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|Title Page
|Letter of transmittal
|Foreword and acknowledgements
|Table of Contents
|Florida's Gulf of Mexico
|Florida's northwest Panhandle Gulf...
|Florida's Lower Gulf Coast
|Florida's Keys
|Full Citation
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|Table of Contents
Title Page
Page i
Page ii
Letter of transmittal
Page iii
Page iv
Foreword and acknowledgements
Page v
Page vi
Table of Contents
Page vii
Page viii
Page ix
Page x
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Florida's Gulf of Mexico
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Florida's northwest Panhandle Gulf Coast
Page 13
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Page 15
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Page 17
Page 18
Page 19
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Page 48
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Florida's Lower Gulf Coast
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Florida's Keys
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|Full Text
David B. Struhs, Secretary
Edwin J. Conklin, Director
Walter Schmidt,: Stte Geologist and Chief
David B. Struhs, Secretary
Edwin J. Conklin, Director
.-. Watffr Schnifit, State Geolokgwst and Chief"'.
SPECt PUBLICATION NO. 48
ANNaTATID ANDI LI"STRATED BIBLIOGRAPHY OF MARINE
SUBAQUk US *ND CRES CES OF FLORIDA'S GULF OT MEXICO
Florida Geological Survey
Governor Jeb Bush
Florida Department of Environmental Protection
Tallahassee, Florida 32301
Dear Governor Bush
The Florida Geological Survey, Division of Resource Assessment and Management,
Department of Environmental Protection, is publishing "Annotated and Illustrated Bibliography of
Marine Subaqueous Sand Resources of Florida's Gulf of Mexico, 1942-1997" as its Special
Publication No. 48. This document shall be of use to the State as a source of information about
Gulf of Mexico sand resources for a variety of purposes. Perhaps the most important purpose is
to identify sources of sand for beach restoration and maintenance purposes.
Respectively yours,
Walter Schmidt, Ph.D., P.G.
State Geologist and Chief
Florida Geological Survey
Printed for the
Florida Geological Survey
Tallahassee, Florida
This work is organized into one short introduction, one section on the Gulf Coast, three
regional sections, and 13 county sections. The Introductory section was written by JHB and edited
by RRC, The Florida Gulf Coast,and regional sections were compiled by JHB based on work
previously written/published by JHB and RRC, with offshore sediment resources compiled by JHB.
General descriptions for the county sections were jointly written by JHB and RRC. Inlet
descriptions were largely written by RRC with updated information about sediment resources
provided by both JHB and RRC. Offshore sand resources for county sections were compiled by
JHB with editorial input and additions provided by RRC. Text and figures were compiled by JHB.
The contents of this work include contributions pursuant to the goal to encompass the
period from about 1942 (when the first quantitative account was reported) to mid- to late-1997, and
includes identification of over 560 bibliographic entries. It was originally intended by the authors
that this work would be updated through the outside and FGS review process to reflect work
accumulated through 2000. However, given the length of the document relative to the time it takes
for the FGS review process to occur and the interruption of computer (PC) resources at the FGS,
it was determined by the State Geologist to publish the work through mid- to late-1997. We hasten
to add that with the amount of investigative material amassed during this 55-year period, there will
be documents not contained in this work. In instances, there are studies which have been reported
by multiple documents, and only the more or most comprehensive of these may be reported herein.
In other cases, we may have entirely missed a publication or report, particularly if it has been
reported or published by an esoteric source, or we simply could not procure a copy. We have
found, through the years, that it is impossible to obtain, let alone read, everything that exists. This
work is the result of our combined experience and knowledge assisted in large part by our own
extensive personal libraries. We have felt it necessary to share with our colleagues in the coastal
geology and coastal engineering community our accumulated "corporate knowledge", that by its
sharing, future endeavors will be rendered more complete and a little less tedious.
All figures included in this compilation are intended to assist the reader with understanding
and clarity of the cited references. We have reproduced them and included them here, generally
in their original form and scale. As a result, some figures contain details and text difficult to
ascertain in this format, with inconsistent use of scale base, north arrows, and longitude/latitude
displays. For complete understanding and additional information the reader should consult the
original referenced document.
To assist the reader in identifying referenced material, references cited in text are in bold
type when they refer to reports and publications that contain and discuss pertinent sedimentologic
information. General references are not printed in bold type.
This document was submitted to an extensive number of entities (consulting firms,
universities, agencies, and individuals requesting an outside review and identification of material
that should be included. A number of highly valuable reviews were forthcoming, accompanied also
by the identification of pertinent data, maps, reports and publications requiring inclusion in the final
work. We gratefully acknowledge the painstaking contributions of the following with thanks:
1) Christopher P. Jones, Earth Tech, Charlottesville, Virginia.
2) Thomas Campbell, Stephen Keehn, and Jeffrey L. Andrews,
Coastal Planning and Engineering, Inc., Boca Raton, Florida.
3) Gregg R. Brooks, Galbraith Marine Science Laboratory, Eckerd
College, St. Petersburg, Florida.
4) Michael T. Poff, Coastal Engineering Consultants, Inc., Naples,
5) Gregory W. Stone, Coastal Studies Institute, Howe-Russell Geoscience
Complex, Louisiana State University, Baton Raton, LA 70803.
We should also like to acknowledge comments on the manuscript forthcoming from Richard E.
Bonner of the U. S. Army Corps of Engineers, Jacksonville District.
The three-part inhouse review process of the Florida Geological Survey was conducted by
Kenneth M. Campbell, Jacqueline M. Lloyd, Deborah E. MeKeel, Thomas M. Scott, and Walter
Schmidt. We gratefully acknowledge their efforts and contributions.
A number of figures published in this work were from copyrighted material, whose release
is here acknowledged.
Figure 2 of this work was forthcoming from Blake and Doyle (1983). Figures 4 and 25
originated with Gould and Stewart (1983). Figure 23 was from Stauble and Warnke (1974), and
Figure 38 came from Gibbs and Davis (1991). We acknowledge the copyright release from the S.
E. P. M. Society for Sedimentary Geology given by Cathleen P. Williams, Executive Director.
Figure 17 is from Stewart and Gorsline (1962). Copyright release was granted by A. G.
Plint, editor of Sedimentology (Blackwell Science, Ltd.).
Figure 11 of this work was from Hyne and Goodell (1967) for which copyright release was
forthcoming from Marine Geology, Elsevier Science through Ms Veennema.
Figure 75 originated with Davis and Klay (1989) for which copyright release was obtained
from the President of the Gulf Coast Association of Geological Societies.
LETTER OF TRANSMITTAL .............................................. iii
FOREW ORD ................ ................. .............. .. ........ v
ACKNOWLEDGEMENTS ..................... .......................... v
CONTENTS ................ ........... ...................... vii
General Description .........................................21
Inlet Sand Resources ............................. ........ .... 23
Pensacola Bay Entrance ................................. 23
Offshore Sand Resources ..................................... 23
General Description ................ ................... ........ 25
Inlet Sand Resources .......................................... 26
Destin East Pass.. .............. ..................... 26
Offshore Sand Resources ................ ...... .............. 27
General Description .........................................29
Inlet Sand Resources .......................................... 30
Offshore Sand Resources .................................... 30
General Description ................ ............. ... ........ 31
Inlet Sand Resources ........................................ 33
Phillips Inlet ..................... ............... ...... 33
St. Andrews Inlet ................... ................ 33
St. Andrews Bay East Entrance ........................... 34
Eloise Inlet .......................................... 34
Mexico Beach Inlet ................................. .34
Offshore Sand Resources .................................... 34
General Description ...........................................39
Inlet Sand Resources ................ ............ ..... ..... 40
St. Joseph Point Channel .......... ................ 40
Indian Pass ..........................................41
Offshore Sand Resources .................................... 41
General Description ...........................................43
Inlet Sand Resources ........................................ 45
Indian Pass .............................................45
West Pass ................ ........................... 45
Bob Sike's Cut ............................ ........ 46
East Pass ............... ................... ........ 46
Ochlochonee Bay Entrance ................................ 47
Apalachicola River ................................... 47
Offshore Sand Resources .................................... 47
General Description ................ ....................... 65
Inlet Sand Resources .................................... .... 70
Hurricane Pass .................. ................. .... 70
Willy's Cut .............................. ............... 71
Dunedin Pass ......................................... 72
Clearwater Pass ............................. ......... 73
John's Pass .................... .................... .74
Blind Pass ........................................... 76
Pass-a-Grille .........................................78
Three Unnam ed Inlets .................................. 78
Bunces Pass ......................................... 79
Egmont Channel, Southwest Channel, and Passage Key Inlet .... 79
Offshore Sand Resources ..................................... 80
General Description ................. ........................ 99
Inlet Sand Resources ...................................... 101
Passage Key Inlet ........................... ......... 101
Longboat Pass ........................................ 101
Offshore Sand Resources ................ ................... 103
General Description ......................................... 111
Inlet Sand Resources .................................... ... 115
New Pass ............................................. 115
Big Sarasota Pass ...................................... 115
Midnight Pass ........... ... .......................... 115
Venice Inlet (Casey's Pass) ............................ 116
Offshore Sand Resources .................................... 116
General Description .........................................129
Inlet Sand Resources ........................... ............ 131
Stum p Pass ............................................ 131
Little Gasparilla Pass ...................... ........ . 131
Gasparilla Pass ................... .................. 131
Offshore Sand Resources .......................... .......... 132
General Description ............................ ..........137
Inlet Sand Resources ......... ........................ . 144
Boca Grande Pass ...................................... 144
Captiva Pass ........................................ 144
Redfish Pass ................ .............. .......... 144
Blind Pass ............ .... ................. ........ 145
San Carlos Bay Entrance ................................ 145
Matanzas Pass ......................................... 145
Big Carlos Pass ....................................... 145
New (Little Carlos) Pass ................................. 145
Big Hickory Pass ......................... .......... 145
Offshore Sand Resources .................................... 146
General Description ........................................... 157
Inlet Sand Resources ................. ............ ... ....... 163
Wiggins Pass ..................................... ... 163
Clam Pass .......................................... 163
Doctor's (Moorings) Pass .......................... . 163
Gordon Pass ......................................... 163
Little Marco Pass ............ ................. 164
Hurricane Pass ............................ .......... 164
Capri Pass.......................... ................164
Big Marco Pass ......................................... 164
Caxambas Pass ....... ............................ 164
Blind Pass ................... ........................ 164
Morgan Pass ......................................... 164
OffshoreSand Resources ................ ................... 164
General Description ........................................181
Tidal Channels ...................... .......... .............. 188
Offshore Sand Resources .................................... 188
1942 1997
James H. Balsillie1, P. G. 167
Ralph R. Clark2, P. E. 23243, P. L. S. 3927
A significant number of investigations have, over the years, been published or otherwise
reported concerning offshore sediments of Florida's Gulf of Mexico. We have attempted in this
work to compile a comprehensive treatment of the subject in a regional, subregional, and
county-by-county basis for Florida's Gulf Coast. We have endeavored to annotate publications
and reports to the extent that the user will have a grasp of the information and area of
applicability of each included work. The user, then, will have information from which they can
decide if it is proper or not to further consult individual works for additional details.
This study has been undertaken to identify what is known about potential sources of
sediment for beach restoration and maintenance renourishment and, perhaps, for other
reasons for Florida's Gulf of Mexico beaches. The process of identifying sediment sources
(borrow material) for beach restoration and maintenance renourishment civil works projects
is one which requires multi-phase treatment. These phases proceed from the general to the
One could expend considerable effort compiling a complex and intricate flowchart
detailing the interactive steps required to identify final selection of borrow material resources.
The process is indeed complex. A cost-shared beach restoration civil works project beginning
with a local sponsor (i.e., city or county), receiving (in Florida) State support and, then,
obtaining funding support from the Federal Government has historically required a time period
exceeding ten years! A somewhat simplified order of considerations includes:
1Geological Investigations Section, The Florida Geological Survey.
20ffice of Beaches and Coastal Systems, Florida Department of Environmental
1. Identify where beach restoration is needed.
2. Identify borrow material site(s).
a. Have the site(s) been previously used, and are
resources available or exhausted?
b. Are resources renewable or do we need to
readjust our management of sand resources (e.g.,
inlet sinks)?
3. Given the existing current economical constraints, is it feasible
to transport the borrow material to the restoration site?
4. If transport is feasible, then:
a. Is the borrow material compatible for
replacement of the native beach material? Is
there, for instance, an acceptably small volume of
fines (i.e., fine-grained sediment, specifically silt
and clay)?
b. Does the borrow material have overfill ratios
and renourishment factors (Krumbein, 1957;
Krumbein and James, 1965; James, 1974, 1975;
Dean, 1974; Hobson, 1977; U. S. Army, 1984)
which render it suitable for placement within given
economic constraints?
5. Have cultural (e.g., antiquities) and environmental issues been
properly adhered to? For instance, for one environment issue,
sea turtle nesting can require annual or seasonal windows in
permissible placement schedules. In turn this depends on
seasonal wave heights, lengths, periods, and water depth
conditions which will critically affect dredging equipment
mobilization and operation.
These are all task-oriented issues which predominately fall within the realm of geological
or earth science purview. There are cases where information exists such as cores yielding
grain-size information for purposes other than identifying potential borrow material resources.
Nevertheless such information provides a clue for further investigationss.
This report constitutes a first overview of the subject and addresses only general
information related to items 1 and 2 above. Item 1 can be treated in a straightforward manner.
In addressing item 2, there is no practical value in considering those reaches of Florida's Gulf
Coast where beach restoration activities will not be needed in the foreseeable future. Such
coastal reaches include the Big Bend, Ten Thousand Islands, Lower Everglades, and Distal
Keys of the Florida Keys (Figure 1). In part, these are protected areas and, in part, do not have
the population and economic pressures to support beach restoration activities. This is not true
of the Panhandle Coast, Lower Gulf Coast, and Lower Florida Keys where storm damage
0 10 20 30 40 Miles
01020 304050 Km
BAY Bay
CHA. Charlotte
CIT Citrus
COL Collier
DIX Dixie
ESC Escambia
FRA Franklin
GUL Gulf
HER Hemando
HIL Hillsborough
JEF -Jefferson
LEE Lee
LEV Levy
MAN Manatee
MON Monroe
OKA Okaloosa
PAS Pasco
PIN PInellas
SAN Santa Rosa
SAR Sarasota
TAY Taylor
WAK Wakulla
WAL Walton
Distal Lower
Keys Keys
Figure 1. Florida Gulf location map showing locations of counties
physiographic reaches (from Balsillie and Clark, 1992).
and coastal
~__ _.
reduction recreational benefits provide a demand for maintenance of beach resources. It is
these areas upon which this study will focus.
Just how a report of this type is to be organized has been a topic of some discussion among
coastal professionals. There are, of course, studies which vary in scope from Gulf wide, to
regional, to subregional, to highly localized. It remains useful to discuss pertinent information
according to such an hierarchy. And so we shall in this report. The question becomes, however,
just how specific and in what manner do we wish to present information so that it is useful for the
task at hand? We recognize that such subjects as coastal and marine geology, physiography, etc.
do not conform to political orjurisdictional boundaries. For the most part, funding for beach-related
civil works projects are related to such boundaries. The "lion's share" of such projects are cost-
shared through Federal, State, and local (county and city) funding sources. Through the years
experience has taught us that a most equitable organizational breakdown is detailed to a county-
by-county basis, in order to produce a user-friendly reference document. There is, however,
always the potential that some counties will have a paucity of information, while others have been
extensively studied. Nevertheless, this report has been organized so that the most detailed or
specific information is specified on a county basis. In all, thirteen counties comprise the three
coastal reaches of concern (Figure 1).
It has also, through experience, become apparent when dealing with beach restoration and
maintenance nourishment projects, that it is difficult to perceive their need unless there is some
modicum of understanding of local conditions. We have such projects, after all, because there are
people (a locally interested and active population) who wish to see beaches maintained for
economically-related recreational/tourism purposes, or because of concerns related to maintenance
of the environment. Even if for no other reason, such description of historical beach and coastal
conditions provides useful information that may not have been compiled elsewhere.
One vital characteristic of local conditions is the identification of historical and current
erosion reaches. Where possible, quantitative erosion rates are used. Although the technology
exists to accomplish determination of quantitative erosion rates for the entire State (e.g., Balsillie,
1985, 1986; Balsillie and others, 1986), they have not for various reasons, been forthcoming. For
this reason, the comprehensive qualitative beach erosion assessments of Clark (1993) for Florida
are for the most part used in this work. Clark (1993) has identified erosion areas as being critical
or non-critical. Critical erosion occurs where development or recreational interests are threatened,
and non-critical erosion where they are not. It is possible, for instance, that a coastal reach is
experiencing significant erosion rates but because there is no adjacent upland development, it is
categorized as non-critical erosion. On the other hand, beaches which have been restored and
renourished are categorized as critical erosion reaches because they invariably have developed
adjacent uplands and we know they are eroding otherwise there would be no reason for
nourishment and maintenance renourishment.
Petroleum prices critically impact the cost of borrow material. Borrow site and placement
destination water depths and seasonal wave conditions pose certain logistical constraints, as do
such factors as annual windows for sea turtle nesting, etc. Beach and coastal barrier widths and
elevations provide, in part, a measure of the amount of sand-sized material that the forces of
nature have to draw upon in order to naturally maintain ocean-fronting beaches. The demand for
beach restoration/maintenance renourishment is dictated by demography.
Inlets can be significant sediment sinks, and important sources of borrow material. Just
how significant depends on such factors as inlet dimensions, whether they are natural, or
developed for navigation purposes and, if so, how the developments are arranged and
maintenance dredging activities are scheduled, etc. Incident wave conditions and astronomical tide
conditions provide for standard geologic inlet classification. Coastal science has resulted in little
understanding of shore-normal sediment transport processes, at least in-so-far as quantification
is possible. However, the importance and quantification of longshore sediment transport processes
is undeniable and possible, and must be specified if inlet sink resources are to be responsibly
An understanding of the above factors and processes is necessary to responsibly design
a search schedule for potential sources of beach restoration/maintenance renourishment material.
Therefore, descriptive overviews of the status of local conditions of Florida's coastal conditions will
accompany each county assessment.
This is an information discovery document. Certain sections contained in this work are
abbreviated accounts, such as discussions of county coastal physiography, geology, littoral
conditions, etc. which are properly covered in sections entitled "general description". Sections on
inlet sand resources can significantly vary in detail because some Florida Gulf Coast inlets have
been intensively studied, others have not. Forthe above, one must refer to cited references to gain
insight as to local, specific conditions. Accounts related to offshore sources of sand provide
information sufficient to generally describe such potential resources; original documents must be
accessed to find specific details.
Regarding this work and, specifically, sand source information, we have not posited any
interpretations of original data. This work, again, constitutes an information discovery document.
Any discrepancies or misinterpretations (other than possible errors in reporting the information) are
not the responsibility of the authors or publishing agency.
It became apparent as we pursued this work that a potentially serious problem may exist.
It pertains to sediment borrow areas whose resources have been partially or substantially exploited.
On land one can easily inspect such borrow areas, i.e., sand pits. The same is not true for offshore
subaqueous areas (note: inlet associated sediment resources pose different logistical concerns that
are more closely monitored). There is currently no known (at least to the authors) system in place
to account for exploited sediment volumes and the location of dredged areas. Following are some
1) Offshore sand resources are not inexhaustible.
2) To survey areas to find no useful resources because they have
been previously dredged would not be dollars well spent in terms of
a sediment search program.
3) However, monitoring of dredged offshore areas would be of
value to determine how and what rate the dredged "holes" fill with
sediment under both normal conditions and from extreme event
4) Wave energy content is a function of water depth. Hence, if we
dredge closer to shore there is the potential that highly destructive
wave energy, particularly during storms and hurricanes, will have
greater destructive impact close to or directly upon our beaches and
5) There exists much sand in deposits lying upon limestone
hardbottom too thin to be excavated by traditional dredging
The bottom line is that we are utilizing offshore sediment resources that lie in the public
domain (with the exception of offshore Spanish land grants and areas used for national defense
purposes), and we are not accounting for their use. To do so would seem to be in our interest and
should not be a difficult action to document. The critical information would be the amount of
material removed and GPS coordinates of the perimeter of the dredged area.
Florida's coast fronting on the Gulf of Mexico has a myriad of unique coastal
environments that deserve recognition. Six general regions can be easily identified, each of
which commonly deserves subdivision (Figure 1). From northwest to southeast these are
identified in Table 1. Following are some general introductory characteristics concerning
Florida's Gulf Coast affecting the task at hand.
Florida has over 747
miles of shoreline fronting directly
on the Gulf of Mexico, of which
about 417 miles are sandy
beaches. Of the sandy beaches,
192 miles are currently
experiencing problematic erosion,
of which 101 miles are considered
critical, and 91 non-critical miles
(Clark, 1993). In addition, there
are at least 3,125 miles of bay and
estuarine shoreline. (Balsillie and
Clark, 1992).
Not counting river
entrances of the Big Bend and
tidal channels of the Ten
Thousand Islands, Lower
Everglades, and the Florida Keys,
sandy beaches of the Gulf are
affected by 55 barrier tidal inlets
resulting, on the average, in an
inlet for every seven miles.
(Balsillie and Clark, 1992).
Table 1. Coastal classification of Florida's Gulf Coast
(from Balsillie and Clark, 1992).
Western Barriers
Middle Mainland
Panhandle Gulf Coast Middle Mainland
San Bias Realignment
Apalachicola-Ochlockonee Barriers
Big Bend
Northern Barriers
Middle Islands
Lower Gulf Coast Charlotte Harbor Complex
San Carlos Reentrant
Southern Barriers
Ten Thousand Islands
Lower Everglades Sloughs Debouchure
Capes of Sable
Lower Keys
Florida Keys Lower Keys
I_ Distal Keys
It is geologically of consequence to note that except for the Apalachicola River
entering the Gulf of Mexico near the eastern part of the Panhandle Gulf Coast (and behind
several barrier islands), rivers discharging into the Gulf do not contribute appreciable quantities
of sediment to the State's Gulf of Mexico coast. (Balsillie and Clark, 1992).
A number of regional studies for Florida's Gulf of Mexico have been conducted.
Following is an overview.
Terrestrial sand resources (borrow material) for restoration and maintenance
renourishment have over the years become, due to transportation costs and increasingly limited
quantities, unable to meet project demands. The last such restoration along Florida's Gulf of
Mexico, occurred in 1989 on Honeymoon Island (Pinellas County) where 230,000 cubic yards
of sand were trucked from an inland site. For some considerable time, now, we have
recognized that littoral and offshore sources of sand deserve exploration. These sources can
be approached in terms of two categories. The first deals with inlets, the second with offshore
Inlets are natural sinks for sediment transported along adjacent shores. Where inlets
are stabilized (e.g., with jetties) and maintained (e.g., dredged) for navigation purposes, inlet
effectiveness as a sediment sink is enhanced and in some cases, where sediment sources are
prolific, may be considered as renewable resources. Prior to the late 1970's early 1980s, it
was common practice to dispose of dredged inlet material in offshore approved disposal sites,
rather than to place material onto the beaches. Bruun (1967) determined that, on the average,
some 11,000,000 cubic yards of sand per year were irremeably lost from Florida's beaches due
to this practice. The State of Florida, led by William T. Carlton (Director, Division of Beaches
and Shores), reversed this policy in the late 1970s.
Of the 55 inlets earlier identified for consideration along Florida's Gulf of Mexico, 19 are
stabilized and/or maintained. In order to responsibly utilize such sediment resources, one
needs to employ a considerable amount of accrued inlet hydraulics knowledge that can be
applied to inlets in general. It is not deemed appropriate here to inventory such inlet research
and results; such a task would be considerable. A few important works include O'Brien (1969),
O'Brien and Clark (1974), Bruun (1978), etc. One might also recognize the work of Mehta and
Montague (1991) who have addressed the issue of how much of an inlet ebb tidal shoal can
be dredged without running the risk of doing undue harm to an inlet. Hine and others (1986)
compiled an informative work which, based on the results of many researchers, provides an
inventory of Florida Gulf of Mexico inlets including their sediment storage capacities. Dean and
O'Brien (1987), using Hine and others (1986) data, published an inventory of Gulf inlets
including aerial photography. Based on the work of Curtis and others (1984) the Office of
Beaches and Coastal Systems, Florida Department of Environmental Protection has been
flying low-altitude video of Florida's coastline and inlet conditions once or twice per year.
Offshore investigation of sand resources for the Gulf of Mexico has not received the
attention given to other coasts. Florida's east coast, for instance, has been subject to the Inner
Continental Shelf Sediment and Structure Program (ICONS) series of investigations (e.g.,
Duane, 1968; Duane and Meisburger, 1969, Meisburger and Duane, 1971; Meisburger and
Field, 1975; Anonymous, 1988) which were specifically designed for the purpose of identifying
sand resources for beach restoration and maintenance renourishment. This program was
never applied to the Gulf of Mexico. That is not to say that there have not been Gulf
investigations related to the needs of this work.
Lowman (1949) published a Gulf-wide study on sedimentary faces of the Gulf Coast;
the account is not, however, sufficient in detail for purposes of this work.
Gould and Stewart (1955) published the first comprehensive regional study on
subaqueous surface sediments for most of Florida's Gulf of Mexico, which we shall extensively
use in this work.
Fairbank (1956) conducted an offshore study of mineral resources extending from the
Mississippi River to the Dry Tortugas. Most sampling occurred along the continental slope.
Moe (1963) compiled an inventory of marine fishing reefs for the entire state. These
reefs are, characteristically, elevated "hard-grounds". The compilation is important because
Moe describes these subaqueous outcrops, and provides depth and location data that can
serve as "marine landmarks".
Bergantino (1971) analyzed bathymetric, magnetic, gravity, and seismic profile data
obtained by the U. S. Navy to identify Gulf of Mexico regional physiography.
Rezack and Edwards (1972) provide an overview of carbonate sediments of the eastern
Gulf of Mexico. Wilhelm and Ewing (1972) published on the geology and history of the Gulf
of Mexico including discussion of several Florida seismic profiles. In general terms Ginsburg
and James (1974) have mapped and discussed bathymetry and facies distribution in the
eastern Gulf of Mexico (see also Reading (1978), p. 276-278). Brooks (1973, 1974) published
a discussion of available information on the geology and surface sediments of the eastern Gulf
of Mexico.
Doyle and Sparks (1980) and Doyle and Feldhausen (1981) discuss MAFLA
(Mississippi-Alabama-Florida) sediment samples, based on mineralogy and texture, for the
Florida Gulf of Mexico continental shelf and provide an interpretation of surface sediment
faces. They conclude (incorporating the work of others (e.g., Gould and Stewart, 1955;
Shepard and Ludwick, 1956; Griffin, 1962; Huang and others, 1975; Pyle and others, 1977;
etc.) that surface sediment character west of Cape San Bias is different than sediment
character to the east and south. West of Cape San Bias the sediments are plastic, become
finer to the west, and are dominated (where clay is present) by smectite. East of San Bias and
along the lower peninsula of the Florida Gulf Coast are three zones of sediment dominated
(where clay is present) by kaolinite. Landward of the 100-meter depth contour there are,
sequentially, a carbonate sand sheet, a carbonate-quartz transition zone, and finally the west
Florida quartz sand sheet. Most of the MAFLA samples are from locations too far seaward to
be useful as a sand resource. Additionally, granulometric analysis was conducted using whole-
phi intervals, which is not useful for assessing potential borrow material for beach placement.
Brooks and others (in manuscript, in preparation) note that the nearshore quartz sand belt
is really a patchy distribution, in some places dominated by quartz sand, but in others by
carbonate material. A representative nearshore collection of the MAFLA surface cores are
housed in the Florida Geological Survey Core Storage Facility, and can be subjected to
granulometric analyses.
The U. S. Minerals Management Service (1983) published a 1:1,200,000 scale map
depicting bottom sediments for the Gulf of Mexico. While the scale does not allow for detailed
bottom sediment character, sand sheets and quartz-carbonate transition zones are indicated.
Based on previously amassed information Blake and Doyle (1983) compiled a surface
sediment facies map of the eastern Gulf of Mexico (Figure 2). Following is an explanation for
the various sediment types.
I MAFLA carbonate sand sheet,
II Carbonate-quartz transition zone,
III West Florida lime mud,
IV West Florida quartz sand belt,
V Destin carbonate facies,
MAFLA quartz sand sheet,
Mississippi pro-delta, and
Mississippi pro-delta/MAFLA quartz sand
sheet transition zone.
Figure 2. Sediment facies map of the eastern Gulf of Mexico (from Blake and Doyle,
1983). See text for description of zones.
As a part of the MAFLA investigation, Neurauter (1979) conducted a bathymetric,
seismic, and side-scan sonar investigation along the west Florida shelf. A network of 52
transects totaling 2,400 miles covered an area from Cape San Bias to the north, to Sanibel
Island to the south, and offshore to a water depth of 656 feet (Figure 3). The study revealed
a multitude of bed form types composed of unconsolidated sediment. They are classified
based on wave length, and ripple index (wave length/wave height), resulting in 4 groups: giant,
large, small-scale ripples, and low-relief swells. Low-relief swells are further defined as
sediment hills of extremely long wave length (usually greater than 1000 m) with comparatively
low relief that is often strongly asymmetric. Five major geographic zones have been identified
according to the distribution of the above bed-form types. The results of this study shall be
addressed in appropriate ensuing sections.
A U. S. Minerals Management Service heavy mineral reconnaissance study
(Anonymous, 1988) was conducted between Alligator Point and Panama City, extending some
Figure 3. Bathymetric, seismic, and side-scan sonar tracks and
bedform regions (A, B, C, D, and E) of Neurauter (1979).
10 to 15 miles offshore. About 200 miles of seismic profiles and 11 cores (6 to 20 feet in
length) were taken. In addition to heavy mineral analyses, general granulometric
characteristics (i e., means and standard deviations) were determined from samples taken from
five of the longest cores.
Hine (1997) has described an overview of the geology of Florida's Gulf of Mexico shelf
The Panhandle Gulf Coast of Florida extends from the Alabama-Florida state line east
to the Ochlokonee River entrance. There are 218 miles of sandy Gulf-fronting beaches and
13 barrier island inlets. In addition, there are 844 miles of interior bay and estuarine shoreline.
(Balsillie and Clark, 1992). Balsillie and Clark (1992) have subdivided the northwest panhandle
Gulf coast into four physiographic coastal reaches that from west to east are: the Western
Barriers, Middle Mainland, San Bias Realignment, and the Apalachicola-Ochlockonee Barriers
(Figure 1).
Placement of subaqueously derived sand on the beaches has not been a prolific activity
along the northwest panhandle. Most maintenance dredging has been disposed of in open
water Gulf sites. In 1959, however, 6.93 million cubic yards of sand dredged from Pensacola
Bay Entrance were placed near the western end of Santa Rosa Island. In 1970 and 1973, 1.15
million cubic yards of sand removed from St. Joseph Point Channel were placed on the end of
St. Joseph Peninsula. These two projects, however, appear to have been based on
convenience rather than the concerted effort to nourish beaches. Shortly following the impact
of Hurricane Eloise in 1975 at Panama City, emergency fill operations were conducted. An
unknown quantity of material was placed on the beaches, but the operation was cut short
because of dredging improprieties. Three bona-fide bypassing projects have been undertaken.
One in 1985 resulted in the transfer of 300,000 cubic yards from maintenance dredging of St.
Joseph Point Channel to St. Joseph Spit. Another occurred in 1973, 1982, and 1985 when
just over 1.0 million cubic yards of maintenance dredging material from St. Andrews Inlet was
bypassed to west the of the inlet on St. Andrews State Recreation Area. The third took place
in the 1970's, when an unknown quantity of sand was bypassed to the west of Bob Sike's Cut.
All of Florida's coasts are subject to extreme event erosion. For the Panhandle Gulf
Coast recent Hurricane impacts (e.g., Hurricanes Alma in 1966, Agnes in 1972, Eloise in 1975,
Frederic in 1979, Elena and Kate in 1985, Erin and Opal in 1995) have all resulted in coastal
erosion. However, for the most part, long-term beach erosion is considered minimal for the
Panhandle, because there are sufficient quantities of sand stored in coastal dunes. Storm
forces erode these natural resources to maintain the beaches fronting them. Faced with
increasing population growth and coastal development, however, this status-quo cannot last.
The ensuing account for the Panhandle Gulf Coast does not refer to extreme event
impacts and their consequences. Related information, however, is available. Some references
include U. S. Army, 1964; 1976; O'Connor and Yon, 1967; Warnke, 1967; Shows and others,
1976; Burdin, 1977; Chiu, 1977; Balsillie and Clark, 1979; Balsillie, 1975, 1983, 1985a, 1986;
Moore, 1983; Nave and others, 1986; Stone, 1984; Morgan and Stone, 1985; Stone and others,
1985; Clark, 1986a, 1986b, 1992; Stone and Salmon, 1988; Stone, 1991; Stone and Morgan,
1993; Stone and others, 1996a, 1996b; and Clark and others, 1995.
A number of regional studies related to offshore sediment sources deserve description,
for which discussion follows.
One of the earliest studies of the region is offered by Goldstein (1942) who described
sedimentologic provinces of the northern Gulf of Mexico.
Gould and Stewart (1955) sampled unconsolidated surface sediments and described
offshore conditions off the
easternmost three counties
(Bay, Gulf, and Franklin) of
the Panhandle Gulf Coast
(Figure 4). Some 165
sediment samples were
obtained. They found that
sand, averaging more than
90% quartz and less than
10% calcareous or organic
matter, covers approximately
75% of the area to an
average distance of 50 miles
offshore. These quartz
sediments were found to be
uniformly composed of fine-
and medium-sized sand.
Seaward of the
predominantly quartz sand
zone lies a narrow belt of
sand-sized unconsolidated
quartz-shell sediment, with
shell being the dominant
component. There were,
however, no descriptions of
thicknesses of the
unconsolidated sediment, nor of bare rock exposures.
Saffir (1955) compared granulometric characteristics of panhandle river (23 samples)
and beach (7 samples) sediments.
Moe's (1963) fishing ground survey introduced earlier, describes offshore bottom
conditions. Locations are given in Figures 5a and 5b; descriptions are listed in Tables 2a and
2b. Only those areas located in water depths of 60 feet or less are considered in this work.
The reader is referred to Moe's work for areas located in deeper water.
Ludwick (1964) describes sand sheets lying adjacent to coastal Florida along its
Panhandle Gulf Coast. To the west (Perdido Key) is the Mississippi-Alabama sand faces
which lies south of the barrier islands to depths of 180 feet some 40 to 50 miles offshore. On
the average these sediments are 93% terrigenous sand, 7% carbonate, and no silt or clay.
Thickness of the deposit is unknown, but probably is less than 50 feet. Carbonate sands are
infrequently found, but when identified are composed largely of broken mollusk shells, with
average particle sizes of 2 to 4 mm. At several places, disarticulated oyster shells have been
found, which were brackish water, not marine, organisms.
To the east (Destin East Pass east to St. George Island) lies the Cape San Bias sand
facies, which has a 70-mile alongshore extent and lies from 25 to 50 miles offshore to water
depths of from 150 to 300 feet. Thickness of the sand sheet is unknown, but probably less than
g FFORAM, SAND & SILT
67 i
Figure 4. Bottom sediment characteristics of offshore eastern
part of the Northwest Panhandle Gulf Coast (from Gould and
Stewart, 1955).
Figure 5a. Fishing ground locations of Moe (1963); see Table 2a for descriptions.
Table 2a.
ueous bottom des .
Figure 5b. Fishing ground locations of Moe (1963); see Table 2b for descriptions.
50 feet. These sediments are 90% terrigenous, 10% carbonate sand, and no silt or clayThere
are some deposits comprised of 25% or more shell material. Excluding these latter deposits
there are three major sand types in the sheet: 1. fine-grained, whitish-gray, well-sorted quartz
sands; 2. medium-grained, gray, moderately well-sorted quartz sand containing some large
quartz and quartzite grains 1.0 to 2.0 mm in diameter; and 3. coarse-grained, yellow-brown,
iron-stained quartz sand containing up to 25% quartz and quartzite grains coarser than 1.0
mm and some 1.5 to 2.5 mm in diameter.
Arthur and others (1986) reported granulometric properties of 250 offshore surface grab
sediment samples for the panhandle Gulf Coast extending from the Florida-Alabama border
east to the Big Bend (Figure 6). Thirty-two north-south transects, separated by an average
distance of 6.0 miles were sampled in May of 1984. The transects, averaging about 11.5 miles
in length, began at a distance of about 3.4 miles offshore. Sampling was conducted at an
interval of 1.1 to 1.7 miles along each transect. Sediments, primarily siliciclastic (Arthur,
personal communication), are interpreted to be fluvial in origin, having been transported to the
Area Loca Name North Depth Bottom Composition and Topography
Longitude Latitude
The 87 19' 300 16' Exposed Sand bottom; wreck of old battleship.
CH-A Massachusetts
CH-B The Sea Buoy 87 14' 30' 14 18 to 60 Rolling sand bottom with rare occurrences of low rock;
to to occasional patches of shell, gravel or grass. One
870 23' 300 17 small privately constructed artificial reef.
CH-D The Sea Buoy 860 24' 300 19' 24 to 78 Sloping flat sand bottom. Very few rock areas; some
to to wreckage present.
860 33' 30 23'
CH-J Trolling Ground 85 39' 300 02' 18 to 72 Sand bottom with rare occurrences of shell and rock.
to to One artificial reef in the area.
860 04' 30" 16
Table 2b. Subaqueous bottom description for fishing grounds (from Moe, 1963).
Area Local Name West North eeth Bottom Composition and Topography
Longitude Latitude
84W 24' 290 33' 36 to 66 Uneven, slightly rolling sand bottom with ridges of
PA-B to to limestone rock and shell parallel or at a slight angle to
840 35' 290 48' the coastline; a few ridges of rock 6 to 8 feet high
scattered through the area
PA-C 84' 00' 29 33' 54 to 78 Hard sand bottom with scattered holes and gullies;
to to broken rock on the edges and bottoms of
86 23' 29" 36' depressions; gently slopes toward deeper water.
PA-D 83 50' 290 37' 12 to 42 Hard sand bottom with a series of gullies running NE
to to and SW in direction with shell and broken rock in
84' 14' 290 57' depressions.
PA-E 84' 07* 290 46' 9 to 42 In vicinity of sea buoy; inshore area with expanses of
to to sand, grass flats, and shell and rock; gentle rolling
84 25' 290 54' relief, extensive sand ridge runs through the area
ridge marked on map.
PA-F 83 50' 290 14' 60 to 66 Flat sand and shell bottom with scattered
to to outcroppings of limestone rock; gentle slope toward
_84 40' 290 26' deep water with mild relief.
Figure 6. Sample locations for the study of Arthur and others (1986).
shelf primarily by the Apalachicola River during low sea level stands of the Pleistocene, and
subsequently reworked by wave activity. The grand mean grain size of sampled sediments is
1.62 (p, ranging from 1.25 (p to 2.87 cp (i.e., medium-sized sand). Standard deviations (sorting
coefficients) ranged from 0.66 grain size from west to east, although there are local trends that may be of consequence. From
Pensacola Bay east to Choctawhatchee Bay sediments decrease in size. East from
Choctawhatchee Bay sediments initially increase in size then decrease in size to St. Andrews
Bay. From St. Andrews Bay southeast, then east to the central part of St. George Island there
a decrease in size, to the east of which grain size markedly decreases. Selective details will
be discussed for respective counties to which they apply.
Locker and others (1988) and Locker and Doyle (1992) logged 1,988 trackline miles of
high precision bathymetry, high resolution seismic reflection data (30-60 feet of penetration),
side scan sonar, (Figure 7a) and 681 surface sediment samples (Figure 7b) in Florida State
waters from the Florida-Alabama border east to St. Joseph Peninsula. Field data, collected in
December of 1986, extended from nearshore to about 18.6 miles offshore. The authors
discuss filled channels associated with fluvial-deltaic "systems". Side scan sonar and high
resolution seismic reflection results do not indicate the widespread presence of outcrops. Most
of the inner shelf is predominantly veneered with medium-sized quartz sand. These sediments
Figure 7a. Bathymetric, seismic, and sonar tracklines for the study of Locker and others
0 c-;-, ____--___ ,,",,
Figure 7b. Surface sediment sample sites for the study of Locker and others (1988).
are low in carbonate content. There is a single, rather large area of shelf mud to the south of
Panama City and southwest of Crooked Island. Patches of very coarse sand occur at the
offshore edge of the study area south of the eastern side of Pensacola Bay, and along the shelf
between Choctawhatchee Bay and Panama City. Side scan sonar interpretations indicate
these latter areas may be associated with outcrops.
Along the inner shelf off Pensacola Bay and along most of Santa Rosa Island,
sonographs show low relief bathymetric swells with sand waves three to ten feet in height.
Outer reaches of the study area from Pensacola to Choctawhatchee Bay also indicate
bedforms ranging from three to ten feet in height, with some ranging in height from 13 to 82
feet, and reticulation ring patterns ranging in diameter from 16 to 23 feet.
From Choctawhatchee Bay east to just west of the vicinity of St. Andrews Inlet, the shelf
is characterized by localized hard-bottoms, reticulation patterns, sand waves, and patchy
reflectivity patterns. Hardbottoms are found mainly within 6.2 miles of shore in water depths
of 65 to 98 feet, with area extents of 330 to 650 feet. Sand waves up to ten feet in height are
common, upon which are superimposed reticulation and patchy patterns.
From just west of St. Andrews Inlet to St. Joseph Peninsula, sediments contain greater
than 5% mud. "Sand ribbons" are present in an extensive band (18.6 miles in width to 6.2
miles in length) normal to shore in water depths up to 66 feet. Elsewhere, the area is
characterized by megaripples and low-relief sand waves decorated with megaripples.
These researchers provide detailed listings and plots (in appendices) of sedimentologic
results including sample location, mean grain size, standard deviation, percent fines, and
percent carbonates, for each of the samples.
Following are detailed county accounts (from west to east) for Florida's Northwest
Panhandle Gulf coast.
Allard (1988) in a heavy mineral study describes 11 shallow cores taken in waters
offshore of Panama City east to St. George Island.
General Description
Escambia County is the westernmost county located along Florida's panhandle coast,
extending from the Alabama-Florida border east to Santa Rosa County (Figure 8). Escambia
County's shoreline possesses 36.5 miles of beach front located on two coastal barriers, Perdido
Key to the west and Santa Rosa Island to the east. This account, also includes a short 4.3-mile
coastal reach lying in Santa Rosa County just east of Escambia County (R-192 to R-214). This
reach was, for years, leased to Escambia County (returned to Santa Rosa County jurisdiction
in 1990).
Gulf-fronting Escambia County
is characterized by barrier island
beaches subject to a moderate wave lli ISlill
energy climate (Tanner, 1960;
Gorsline, 1966; Balsillie, 1975). Mean
range of tide varies from 1.23 feet at
the western end of the county to 1.27 z. ic
feet at the eastern end (Balsillie and
others, 1987; Balsillie, 1987). The
Gulf-fronting beaches of Escambia R4 0-so ..-
County experience net annual -0111 ,""
westward longshore transport (Balsillie,
1975, 1977; Stapor, 1975, Stone, 1991; B Entr...
Stone and others, 1992), although, like GULF OF MEXICO
the remainder of the panhandle, daily
to weekly transport reversals appear to
occur rather than seasonal reversals.! T ..
Perdido Key, the westernmost
barrier, is 15 miles long, of which the . ..
western 1.7 miles are located in
Alabama. Once connected to the ...".'
mainland by a low marshy area in the R..
vicinity of Gulf Beach, dredging of the R- .-., "' "
Intracoastal Waterway has separated R.1o *"
Perdido Key from the mainland. The .,o "" "
widest portion of Perdido Key is close "*""~ ah GULF OF MEXICO
to 6,200 feet near its center. From the
Alabama State line to Gulf Beach, the Figure 8. Escambia County coastal map
key ranges from 900 to 2,000 feet in showing locations of every tenth DNR
width, and to the east of Gulf Beach reference monument.
ranges in width from 500 to 2,000 feet
Fischer and others, 1984). Dune heights average about 20 feet along the central portion of the
key decreasing toward each end with the dunes becoming discrete mounds. The dune toe (i.e.,
the beach/coast intersection or nickpoint) averages 6 to 10 feet above mean sea level, and is
generally well anchored by vegetation. The eastern end of Perdido Key terminates at
Pensacola Bay Entrance.
Long-term historical shoreline change rate studies for Escambia County have been by
Kwon (1969); U. S. Army (1971), Stapor (1975), Balsillie and others (1986), and Clark (1993).
The following account is based, unless otherwise noted, on the results of Balsillie and others
(1986) using eight surveys for the period 1856 to 1985. The coastal reach from the Florida-
Alabama line to the east five miles (i.e., DNR reference monuments R-1 to R-27) along Perdido
Key is accreting to stable with maximum accretion of 2.8 feet per year occurring at R-1 and
decreasing to a stable shoreline near R-27. Proceeding to the east, the shoreline has an
erosion history reaching a maximum value of -5.68 feet per year at R-52 (5.02 miles east of R-
27), thereafter decreasing to -0.54 feet per year just east of the Pensacola Bay Entrance near
R-66 (7.46 miles east of R-27). Immediately west of the bay entrance at R-67, the shoreline
has been experiencing an erosion rate of -1.45 feet per year. Clark (1993) describes the
erosion from R-31 to R-65 as noncritical.
Santa Rosa Island, to the east of Pensacola Bay Entrance, is 50 miles in length and
represents the longest unbroken stretch of beach in the eastern Gulf of Mexico, and terminates
at East Pass, near Destin in Okaloosa County. Approximately 27 miles of Santa Rosa Island
are located within Escambia County. It is a narrow barrier island, ranging from 600 to 3,500
feet in width, averaging 2,000 feet. The barrier is composed of a single, well defined primary
dune ridge, backed by a lower swale and numerous large secondary dunes. At its western
end, the island fronts on Pensacola Bay; the remainder of the island is separated from the
mainland peninsula by Santa Rosa Sound. The Gulf-fronting beaches average 100 to 125 feet
in width, and are backed by dunes averaging 16 feet, except in the vicinity of Sabine Bay and
near Fort Pickens on the western end, where dunes attain heights of up to 40 feet (Fischer and
others, 1984). However, some of the high sand bodies around Fort Pickens appear to be
associated with old gun emplacements and may not be natural features. The narrow width of
the island makes it subject to local storm tide washover during major storms and a number of
washover fans are evident from aerial photographs (Stone and Salmon, 1988; Stone, 1991;
Stone and others, 1996). Santa Rosa Island is an area of active dune migration, and near the
western end salt marsh peat is exposed on the foreshore (Wolfe and others, 1988). The
foreshore slope is relatively steep, especially towards the eastern portions of the island, and
hence, the area has recorded some of the highest waves in the northeast Gulf of Mexico
(Gorsline, 1966; Stone and Morgan, 1993).
The western end of Santa Rosa Island (about 1.5 miles) has a history of tip extension
and erosion and shoreline accretion and recession depending upon the time frame consulted.
Such shifts are not surprising given the prevalent inlet dynamics of a nonstabilized inlet. From
R-78 to R-99, a four-mile reach, erosion rates increase from approximately stable to -4.5 feet
per year. From R-99 to R-184, a 16-mile segment, erosion rates decrease from -4.5 feet per
year to -1.0 feet per year. Clark (1993) defines the erosion from R-79 to R-110 (2.4 miles) as
noncritical on the basis of the lack of threat to development or recreation interests along the
Fort Pickens part of the Gulf Islands National Seashore. From R-110 to R-136 (4.8 miles) he
describes the erosion as critical due to the threat to coastal development. This designation was
confirmed by the impact of Hurricane Opal which destroyed some 90 single-family dwellings
and damaged or destroyed 84 hotel/condominium units and 18 other major structures (Clark
and others, 1995). From R-184 to R-204, a 3.8 mile reach, erosion rates are generally less
than -1.0 feet per year. Eastward from R-204 to the Escambia-Santa Rosa County line near
R-213, erosion rates appear to somewhat increase.
Inlet Sand Resources
Pensacola Bay Entrance: Pensacola Bay Entrance separating Perdido Key and Santa
Rosa Island, is considered to be a "complete littoral barrier" by the U. S. Army (1971). (Hine
and others (1986) have published an extensive, detailed list of dredging activities for the inlet).
Between 1885 and 1985, the U. S. Army, Corps of Engineers has performed hopper dredge
channel deepening and maintenance dredging. Some 35,572,000 cubic yards of material have
been removed, with all but 6,930,000 cubic yards disposed in an offshore open water site The
latter quantity was placed on Santa Rosa Point in 1959 (Hine and others, 1986). Based on a
1984 National Ocean Survey bathymetric survey, the ebb tidal shoals are capable of storing
about 18,030,000 cubic yards of sand (Hine and others, 1986). The removal of sand by
dredging from the entrance ebb tidal shoal, may have resulted in Gulf-fronting shoreline
recession of adjacent barrier island ends. (Balsillie and others, 1990). In 1991 the channel
was deepened to accommodate Navy navigation requirements, and the dredged material
placed on Perdido Key. No more recent dredging of the entrance channel or in the bay has
occurred. The entrance channel has filled at a rate of some 300,000 cubic yards of sediment
Offshore Sand Resources
Parker (1968) collected 30 surface samples offshore of Perdido Key. All but one of the
samples were obtained in water depths of from ten to 30 feet. One sample, offshore of the
entrance to Pensacola Bay, was obtained in a water depth of 60 feet. Trend statistics for mean
grain size and per cent carbonate content are illustrated in Figures 9a and 9b, although the
author also produced trend statistics for standard deviation, skewness, and percentages of
sand, silt, and clay. Average granulometric characteristics and ranges of values of offshore
sediments are listed in Table 3.
PHI MEAN GRAIN SIZE PERCENT CARMBtiNATE
Figure 9a. Offshore mean grain size seaward Figure 9b. Offshore carbonate content
of Perdido Key (from Parker, 1968). seaward of Perdido Key (from Parker, 1968).
Table 3. Granulometric characteristics of Parker (1968).
Parameter Average Range
Mean Grain Size ((p) 1.70 0.92 to 2.47
Standard Deviation (cp) 0.60 0.40 to 1.60
Skewness -0.40 -1.55 to 0.25
Kurtosis 5.25 -0.49 to 21.64
% Sand 99.15 91.94 to 99.97
% Silt 0.060 0.00 to 0.610
% Clay 0.16 0.00 to 1.10
% Gravel 0.64 0.00 to 8.03
% CaCOA 3.09 0.57 to 19.34
Jagger and others (1991) note the existence of a
offshore of the eastern end of Perdido Key.
shoal (Caucus Shoal) 0.8 1.6 miles
General Description
Okaloosa County is located on Florida's Panhandle Gulf Coast between Santa Rosa
County to the west and Bay County to the east (Figure 10). Of the 23.9 miles of the county's
Gulf-fronting shoreline, 13.9 miles are Federal property (Eglin Air Force Base, 10.1 miles east
from the Okaloosa-Santa Rosa County line, and 3.8 miles west of Destin East Pass).
Tanner (1960) describes
Okaloosa County as having I
moderate shoreline energy 4 .
conditions (i.e., breaker heights f .
ranging from 0.33 to 1.64 feet).
The mean range of tide ranges : .
from 1.28 feet at the western
end of the county to 1.29 at the : : :
eastern end (Balsillie and others,
1987; Balsillie, 1987). Net
annual longshore transport is to Pe.
the west (Balsillie, 1975, 1977; "" .
Stone, 1991; Stone and others, Hody
1992; Stone and Stapor, 1996),
although like the rest of the
Panhandle Gulf Coast, daily to 2 UL OF MEXICO
weekly transport reversals tz
appear to occur rather than
seasonal reversals (Balsillie, Figure 10. Okaloosa County coastal map showing
1975, 1977). the locations of every tenth DNR reference
The western 17 miles of
the county's shoreline fronts Santa Rosa Island, an elongate barrier separated from the
mainland by Santa Rosa Sound. Santa Rosa Island extends through three counties,
terminating to the west at Pensacola Bay Entrance in Escambia County. The eastern end of
the island terminates at East Pass (or Destin East Pass), the entrance to Choctawhatchee Bay.
The City of Destin lies to the east of the inlet on the western tip of Moreno Point, a Pleistocene
coastal barrier (Stone, 1991) peninsula which lies between Choctawhatchee Bay and the Gulf
of Mexico. East Pass (Destin East Pass) divides the county into two distinct coastal
physiographies. Santa Rosa Island to the west is a relatively recent geological feature, a
barrier island which was formed during the Holocene era (within the last 10,000 years; Otvos,
1982). To the east, however, the peninsula is a more ancient feature which was formed during
the Pleistocene era and is overlain by a belt of recent beaches (Fischer and others, 1984).
Santa Rosa Island ranges in width from 1,200 to 3,000 feet. Dune heights range from
12 to 22 feet and beach widths average around 185 feet (Fischer and others, 1984). Moreno
Point peninsula ranges in width from about 7,250 to over 12,000 feet. Primary dune heights
range from ten to about 30 feet and beach widths average around 250 feet. West of the pass,
Stapor (1975) found ongoing erosion (also U. S. Army, 1971) to a point 5.5 miles west of the
pass which has been accreting; west of this point the beaches appear to be stable. The
erosion is, in large part, a direct result of inlet modification. The pass has been dredged on
several occasions; however, very little of the dredged material has been placed directly on the
beach. Material has been placed in open water areas and the littoral zone to the west of the
west jetty; however, it has not been determined if the placement of that material has had any
beneficial effect to either the eroding shoreline or to the beaches west of the erosion area. The
1.7-mile eroding reach is not considered critically eroding because the reach is within Eglin Air
Force Base and except for two facilities that were destroyed by Hurricane Opal remains, for the
most part, undeveloped. However, of concern are the beaches west of the Air Force Base (R-1
through R-16). This area, known as Okaloosa Island, is highly developed and, although the
development appears to have been relatively well sited and although there appear to be no
erosion problems in the area at this time, it is not known how long this favorable condition will
continue. It is known that there is no new sand being introduced into the system from offshore
(particularly dredged material from inlet channel maintenance which is disposed offshore).
Thus, this area depends on the westward movement of sand, which is interrupted by East Pass
(Balsillie and others, 1990; Clark, 1993); Stone and Stapor (1996) discuss the inner shelf
sediment budget. Hurricane Opal's impact on this area was severe with all dunes eroded from
overwash processes. Some artificial dune reconstruction has occurred. For the most part,
however, lowered coastal elevations render the area vulnerable to future extreme event impact.
East of Destin East Pass, a barrier beach peninsula extends approximately 2.3 miles
to the east where it merges with the foredune line. This large sand spit, known as Norriego
Point (Holiday Isles), is the remnant eastern tip of Santa Rosa Island, which was cut off when
the present pass was formed in 1928, then shoaled and became attached to the mainland in
1938. Norreigo Point is separated from the mainland by Destin Harbor (Old Pass Lagoon) a
narrow, shallow waterway (Balsillie, 1980; Stone, 1991). Substantial shoreline accretion has
occurred east of East Pass due to jetty construction while the shoreline west of the pass is
undergoing non-critical erosion for about 1.7 miles (Clark, 1993). East of Destin, the mainland
beaches have long been considered to be experiencing net long-term erosion (Stapor, 1975;
Kwon, 1969), although for the period 1934-1969 Stapor (1975) could detect no net erosion.
Just to the east of Destin East Pass at Holiday Isles, the adjacent shoreline accreted
significantly immediately following construction of jetties in 1967; since about 1970 the
shoreline has been stable (Balsillie, 1980). The nature of accretion attests to the westward net
longshore transport along Okaloosa County (Stapor, 1975; Balsillie, 1975, 1977, 1980; Stone
and Stapor, 1996).
Inlet Sand Resources
Destin East Pass: Destin East Pass (Choctawhatchee Bay Entrance or East Pass) is
a natural barrier beach inlet between a land mass called Moreno Point and Santa Rosa Island
and connects the Gulf of Mexico to Choctawhatchee Bay. The present pass was originally
opened during a severe storm in April, 1928, and was enlarged by a record rainfall event in
March, 1929. Previously, an old inlet had existed 1.5 miles to the east, but with the creation
of the new inlet, the old pass shoaled until closure in 1938. The pass was stabilized by the
construction of two boulder mound jetties between October, 1967 and January, 1969. The east
jetty is approximately 2,400 feet in length. The west jetty is approximately 3,200 feet in length
with a 1,000 foot weir section designed to permit passage of littoral sediment into a dredged
deposition basin.
The history of Destin East Pass has been colorful (U. S. Army, 1964a, 1964b; Snetzer,
1969; Parker, 1979; Balsillie, 1980; Sargent, 1988), because the wier section was placed on
the wrong side of the inlet. The inlet weir system was designed with an understanding of the
old inlet channel's eastward migration trend (Snetzer, 1969). In reality, the predominant
longshore transport is to the west (U. S. Army, 1964b; Gorsline, 1966; Walton, 1973, Balsillie,
1975; Stone, 1991; Stone and others, 1992; Stone and Stapor, 1996). Substantial shoreline
accretion has occurred east of the inlet due to jetty construction (Balsillie, 1980). In contrast,
the Santa Rosa Island shoreline to the west of the inlet has eroded for 1.7 miles.
Between 1931 and 1984, the U. S. Army dredged 4,421,721 cubic yards of sand from
the entrance channel, Old Pass Lagoon channel, and deposition basin (Hine and others, 1986).
Between 1969 and 1977, nearly 600,000 cubic yards were reported to have been bypassed to
the beach west of the inlet (Jones, 1977); however, much of this material appears to have been
placed within the open water area and littoral zone to the west of the west jetty with little direct
beach disposal. Much of the additional material dredged was used to build sand dikes. The
ebb tidal shoals have been estimated to store approximately 8.2 million cubic yards of sediment
(Hine and others, 1986); more recent information is available from Stone (1991).
Offshore Sand Resources
Hyne and Goodell (1967) investigated sediments and submarine geomorphology (Figure
11) of the inner continental shelf off of Okaloosa County and western portion of Walton County.
Figure 11. Baythmetry and sand bodies off Destin East Pass
(from Hyne and Goodell, 1967).
They found the inner continental shelf in the area had sinusoidal, submarine ridges and troughs
oriented roughly 70 degrees to the shoreline. Two linear sand bodies were identified lying in
70 feet and 90 feet of water.
General Description
Walton County, located in the central region of Florida's Panhandle between Okaloosa
County to the west and Bay County to the east, has a Gulf-fronting shoreline of 25.6 miles
(Figure 12). There are no true barrier islands in Walton County, although the western two thirds
of the Gulf-front is located
on a coastal peninsula,
extending to the west from Choctw n.tcOee B.
the mainland and forming ..
Choctawhatchee Bay. The I . ..
eastern part of the county is. .
characterized by mainland '.
beaches. Significantly IJ -i -I O a"; "
higher elevations indicate / ..:
that this peninsula is an ", ..R-'. o .
eastward continuation of the ,
Pleistocene barrier complex .
that extends across the eO R-
southern mainland of 2 , R-120o
Escambia, Santa Rosa and a ..-1 3 GULF OF MEXICO SO
Okaloosa Counties and is
here truncated by the Gulf Figure 12. Walton County coastal map showing
shoreline. The peninsula is locations of every tenth DNR reference monument.
characterized by a 10 to 20
foot escarpment on the seaward side with a beach and dune field paralleling the scarp, which,
in some places have overlapped lower parts of the Pleistocene sediments. The terrain upland
of the beach is drained by a number of small streams flowing both to the Bay and to the Gulf.
The result is a series of small to medium-sized freshwater lakes along the shoreline north of
the beach with seasonal or intermittent openings into the Gulf through the dunes. These areas
fill with water from gulfward flowing streams which drain the higher mainland area and are
restricted on the Gulf side by the formation of sand dunes. Under extreme water discharge
conditions, these coastal lakes occasionally breach the dune line and drain directly into the
Gulf. Littorally transported sand tends to seal off the mouths of these lakes soon after the
outlets are formed. Longshore transport rates are discussed by Stone and others (1992) and
Stone and Stapor (1996).
Primary dune elevations range from 12 to 45 feet and average about 26 feet (Fischer
and others, 1984). The high dune elevations are partly due to the presence of the Pleistocene
bluffs, upon which modern dunes form. About three miles west of the Bay-Walton County line,
the average dune elevation is about 30 feet, and maintains this elevation for about 12 miles
before gradually dropping to about 15 feet. Beach widths range from 100 to 500 feet and
average approximately 200 feet (Fischer and others, 1984). The beaches are relatively flat,
but the nearshore gradient is among the steepest in Florida.
The moderate wave energy shoreline (Tanner, 1960; Gorsline, 1966; Balsillie, 1975,
1977) of Walton County is one of two coastal Florida counties without a coastal barrier inlet (the
other being Flagler County on Florida's east coast). The mean range of tide varies from 1.29
feet at the western end of the county to 1.25 at the eastern end (Balsillie and others, 1987,
1990; Balsillie, 1987a). The U. S. Army (1971) reports that during the period 1868 to 1935, the
shoreline of Walton County had a history of erosion, ranging from -0.34 to -0.67 feet per year.
However, since 1935, Walton County's shoreline appears to have stabilized (U. S. Army, 1971;
Stapor, 1975), and Clark (1993) reports "no erosion problem areas" along the Gulf-fronting
beaches. The stability of Walton County's nearshore profile has been described by Balsillie
(1987b) and by Stone and Stapor (1996). Walton County has been impacted by tropical storms
and hurricanes (Balsillie, 1975); Hurricanes Eloise and Opal resulted in considerable erosion
(Burdin, 1977; Chiu, 1977; Balsillie, 1983).
Inlet Sand Resources
There are no inlets in Walton County.
Offshore Sand Resources
Hyne and Goodell (1967) investigated sediments and submarine geomorphology of the
inner continental shelf off of Okaloosa County and western portion of Walton County (Figure
11). They found the inner continental shelf in the area had sinusoidal, submarine ridges and
troughs oriented roughly 70 degrees to the shoreline. Two linear sand bodies were identified
lying in 70 feet and 90 feet of water.
General Description
Bay County is located along the central portion of Florida's Panhandle Gulf Coast
between Walton County to the west and Gulf County to the east (Figure 13). Bay County's
Gulf-fronting shoreline is characterized by mainland beaches in the western section and a
series of barrier islands and spits along the central and eastern reaches. Of the 43.6 miles of
gulf fronting beaches in Bay County, 18.2 miles
are mainland barrier beaches, and the
remainder are barrier island beaches. In *"-"
addition, approximately 17 miles, including the ,i,
eastern portion of Shell Island and all of /M" R20
Crooked Island, are held under Federal pM .t ,I ""q 0 .
ownership. The entire county falls within the "
moderate wave energy category (Tanner, 1960; " .
Gorsline, 1966; Balsillie, 1975). The mean P-w, c, V _,.
range of tide varies slightly from 1.25 feet at o Ba "
the western end of the county to 1.22 feet at 'o "a 0W 62 ,
the eastern end (Balsillie and others, 1987, St. Andrw* it
1990; Balsillie, 1987). , 3 R
mIle She Ilalnd
The western 13 miles of the coastline, a
mainland reach, is similar to that of adjacent East~'"'" : l :
Walton County, a modem beach/dune system -
backed by ten to 20 foot high Pleistocene / :i:
bluffs. Lake Powell located at the western end S,. Andw. Bay-
of the county just landward of the beach and Eal Entrance (' .
dune is a significant feature. As with similar -
features in Walton County, Lake Powell is Cok.d I "d 1% ;
thought to have formed in what were stream Eloe e:.
valleys during the last ice age. These areas fill :::
with water from gulfward flowing streams which o, o L : .
4 Mexico Beach Inlet R
drain the higher mainland area and are 3 ,o :
restricted on the Gulf side by the formation of .. "
sand dunes. Under extreme water discharge
conditions, these coastal lakes occasionally Figure 13. Bay County coastal map
breach the dune line and drain directly into the showing locations of every tenth
Gulf. East from Lake Powell, the shore is DNR reference monument
characterized by mainland beaches extending to the vicinity of Panama City Beach. Here, a
barrier spit has formed, trending to the southeast across the entrance to St. Andrews Bay. The
barrier spit has been bisected by the dredging of a navigation channel (St. Andrews Inlet or the
Panama City Shipping Channel) into St. Andrews Bay, creating Shell Island to the east, which
extends eastward for approximately 6.2 miles, although accretion continues on its eastern tip.
Continuing to the southeast, there is a short reach of mainland beach along which a
cuspate spit has formed (Dog Island, located just to the east of St. Andrews Bay East
Entrance). This area appears to be one of confluence of two longshore transport cells. To the
west, along Shell Island, net annual longshore transport is to the east, which at least in part lies
seaward of Dog Island (Stapor, 1973; Stone and Stapor, 1996).
To the southeast, along Crooked Island, the net annual longshore transport is to the
northwest. Crooked Island, which is separated from the mainland by St. Andrews Sound is now
attached to the mainland at the southeastern end. A recently formed inlet (Eloise Inlet) opened
about midway along the length of the barrier to compensate for the natural closure of the
sound's southeastern end. Hurricane Opal opened yet another inlet nearby. Southeast of the
southern end of Crooked Island there is again a reach of mainland beach which extends to the
Gulf County line. Net annual longshore transport along this reach is to the southeast (Stapor,
1973; Stone and Stapor, 1996).
The barrier spit west of St. Andrews Inlet is separated from the mainland by Grand
Lagoon, and ranges in width from about 1,300 to 1,500 feet. Shell Island ranges from 600 to
4,000 feet in width and Crooked Island ranges in width from about 300 to 2,800 feet. Dunes,
where present, range in elevation from ten to 25 feet with the higher elevations associated with
dunes overlapping the Pleistocene bluff. The average dune elevation is about 17 feet (Fischer
and others, 1984). The primary dune has essentially been eliminated throughout the City of
Panama City Beach and adjacent areas. Beaches along the reach were severely eroded by
Hurricane Opal and are in need of restoration.
Assessment of Bay County shore history is a subject complicated by drift reversals;
natural integration, fragmentation and reintegration of peninsulas; and anthropic activities
including coastal development and inlet construction and stabilization. Except for a 1.7 mile
reach from DNR reference monuments R-40 to R-49, which appears to be stable, all of Bay
County is experiencing shoreline erosion which has been quantified by Balsillie and others
(1986). The western segment from R-1 to R-40 (7.47 miles) is experiencing erosion of less
than -2.1 feet per year, with the maximum of -2.1 feet per year occurring at R-5 (Balsillie and
others, 1986). The segments from R-6 to R-14 and R-17 to R-20 are described by Clark (1993)
as undergoing critical erosion. From R-50 to St. Andrews Inlet at R-97, a distance of 8.9 miles,
the historical erosion rate increases to a maximum of -8 feet year at R-90 and R-91, 1.1 miles
west of St. Andrews Inlet (Balsillie and others, 1986). Clark (1993) describes the segment from
R-63 to R-97 as experiencing critical erosion. Various investigators (e.g., Stapor, 1973; Dean,
1987) have suggested that the 1934 construction of the St. Andrews Inlet and twin rubble jetties
(U. S. Army, 1971, 1976; Sargent, 1988; Lillycrop and others, 1989) is the primary cause of
erosion to the west. From 1934 to 1988 about 12.8 million cubic yards of sand have been
dredged from the inlet of which only 1.04 million cubic yards have been bypassed to the west,
and the remainder deposited offshore (U. S. Army, 1971; Hine and others, 1986). The U. S.
Army (1976) reports that effects of the construction and maintenance of the inlet extend about
2.6 miles west of the inlet, and that west of this area sediment losses can be attributed to
natural erosion processes.
Stapor (1973) located a drift divide just east of St. Andrews Inlet, with net westerly
longshore transport occurring to the west of the inlet and net easterly transport occurring along
Shell Island to the east of the inlet. Unlike seasonal reversals in longshore transport
characteristic along north-south trending shorelines, Balsillie (1975) found that along the east-
west trending Florida panhandle coast drift reversals are daily to weekly rather than seasonal.
Shell Island from R-98 to R-107 is eroding at increasing rates from -1.74 feet per year at R-98
to -6.41 feet per year at R-107. Clark (1993) reports the erosion to be noncritical due to the
lack of coastal development. Stapor (1973) attributes an alteration in the tidal return flow
pattern, effected by the cutting of St. Andrews Inlet, as probably responsible for landward
migration of Shell Island.
Southeast of Shell Island is a 17 mile coastal reach of federal ownership which includes
Dog and Crooked Islands. Stapor (1973; Stone and Stapor, 1996) provides a detailed history
of barrier island formation and migration and sediment budget.
Southeast of the base of Crooked Island to the Bay-Gulf County line (R-122 to R-144)
is a 3.9 mile coastal reach which includes the town of Mexico Beach and Mexico Beach Inlet.
Mexico Beach Inlet at R-127 is a small, inefficient pass with short twin jetties. Net
southeastward longshore transport tends to close the inlet, and some sand bypassing to the
southeast has been accomplished. The beach fronting the town of Mexico Beach from R-127
to R-144 is experiencing critical erosion (U. S. Army, 1971; Clark, 1993).
Inlet Sand Resources
Phillips Inlet: Smallest of the northwest Florida inlets, Phillips Inlet connects Lake Powell with
the Gulf of Mexico in western Bay County. Although Lake Powell is fed by several small
intermittent streams, the predominant tidal prism affecting the inlet/bay system is the volume
of water displaced by the 1.18 foot mean tide range over the lake's 657 acres. Phillips Inlet
periodically opens and closes, but an inlet appears to have existed throughout modern history
as Lake Powell has all the characteristics of an established estuary (Environmental Protection
Systems, Inc., 1985). The inlet's hydraulic and stability characteristics reflect behavior as both
a tidal and an overwash channel (Mehta, 1985). When open, the inlet is approximately 100 feet
wide and only two to three feet deep. The earliest government surveys do show the inlet
existing in 1855.
St. Andrews Inlet: St. Andrews Inlet (also known as the Panama City Shipping Channel or
Land's End Canal), located east of Panama City Beach, is an artificially cut tidal channel
connecting St. Andrews Bay with the Gulf of Mexico. The inlet excavation project was
completed in 1934 as part of the Public Works Program under the National Industrial Recovery
Act. With the construction of this new project and the abandonment of the historic eastern
entrance to St. Andrews Bay, St. Andrews Inlet became the predominant navigation route for
Panama City commerce. Two granite boulder mound jetties spaced 1,500 feet apart were
constructed in 1934. Initial jetty lengths were about 500 feet; however, significant shoreline
recession within the inlet necessitated lengthening the jetties along the inlet's interior shoreline.
In 1935, the east jetty was lengthened to 800 feet and the west jetty to 1,050 feet. The
hurricane of July 31, 1936, caused extensive damage to the jetties, but repairs during 1937 and
1938 extended the east jetty by 210 feet and the west jetty by 270 feet. Between 1939 and
1942, the east jetty was extended another 680 feet and the west jetty was extended by 800
The net annual longshore transport at Panama City Beach has been calculated to be
a westward (Stapor, 1973; Walton, 1973; Balsillie, 1975; Wang and others, 1978; and Walton,
1979). Outer shoals of the inlet store an estimated 2.8 million cubic yards of sediment (Hine
and others, 1986). Subsequent to the 1934 removal of approximately 2.8 million cubic yards
of sediment for the inlet excavation project, the U. S. Army, Corps of Engineers conducted
approximately ten million cubic yards of maintenance dredging from 1935 through 1985. The
channel is authorized to a depth of 42 feet, but currently only dredged to the prior
authorized depth of 32 feet. Sand waves as high as 15 feet are a continuing problem at the
entrance channel and require dredging every 18 months (Lillycrop and others, 1989). Inlet
sand transfer was conducted in 1973, 1982, and 1985 and involved the placement of over one
million cubic yards of sand on the beach at St. Andrews State Recreation Area west of the inlet.
St. Andrews Bay East Entrance: The large natural pass at the east end of Shell Island is the
historic navigation channel into St. Andrews Bay. Maintenance of this navigation channel was
discontinued after the new inlet was cut in 1934. Between 1911 and 1934, the Corps of
Engineers dredged 6,144,163 cubic yards of material from the channel; however, the area of
disposal is not known (Hine and others, 1986). The ebb tidal shoal has been estimated to store
as much as 30 million cubic yards of sand. The shoal dynamics are complex in this area, but
the material storage may be increasing due to the southeastward longshore transport of
sediment along the east end of Shell Island. The east end of Shell Island prograded over 4,000
feet between 1870 and 1977. The excess eastward transport of sediment which does not
materially increase the length of Shell Island continues across the ebb tidal shoals (estimated
at 32,000 cubic yards per year by Stapor, 1973). The inlet is in the process of closure due to
natural littoral transport processes.
Eloise Inlet: The coastal barrier historically referred to as Crooked Island extends for over nine
miles of gulf beach in eastern Bay County. Three former inlets have existed within the Crooked
Island system since the earliest maps published by J. F. W. Des Barres in 1779 (Stapor, 1973).
Further details are discussed by Stapor (1973) and Balsillie and others (1990). Eloise Inlet
was created on the morning of September 23, 1975, when Hurricane Eloise made landfall in
Bay County with the eye passing near Phillips Inlet. It has since exhibited stability and
continues as a classical single inlet-bay system. Stapor (1973) identified this area as a drift
divide, a factor which should further affect the future of the inlet. Eloise Inlet widened as the
result of impact of Hurricane Opal on October 4, 1995, and another inlet formed nearby.
Although Eloise Inlet is of little commercial importance, an investigation of its flow
characteristics would further the state of knowledge of tidal inlet hydraulics and stability. There
are no surveys detailing sediment storage capacity.
Mexico Beach Inlet: Near the southeast end of Bay County is a maintained tidal entrance,
called Mexico Beach Inlet, connecting the Gulf of Mexico to an interior canal system. Another,
unmaintained, Gulf outlet to the canal system exists 10,000 feet to the southeast. The canal
system was developed from a small creek during the 1950's (Jones, 1977). Because there
is an insufficient tidal prism needed for sufficient scouring of the entrance channel, shoaling is
an intermittent problem. The inlet is 60 feet wide and varies in depth from three to five feet at
the entrance. The west jetty is 150 feet long and the east jetty is 130 feet in length. The west
jetty projects 100 feet further Gulfward than the east jetty. The longshore transport of sand is
predominantly eastward. There is little westward transport given the sheltering effect of St.
Joseph Peninsula to the east. For further details about the inlet see U. S. Army (1976), Jones
(1977), and Balsillie and others (1990). Inlet sediment holding capacity has not been
Offshore Sand Resources
Following impact of Hurricane Eloise in 1975, emergency fill activity for Panama City
beach was undertaken. Offshore sediments were obtained by dredging. However, the dredge
began removing sediments from the second offshore bar rather than the designated borrow
area located further offshore. Dredging operations were stopped, and no further fill placement
was conducted.
Preliminary investigations for a source of compatible borrow material for Panama City
beaches (Panama City Shipping Channel west to Phillips Inlet) were conducted in the early-to-
mid 1970s. A more extensive sand exploration program was completed in 1984 when 192
offshore cores, nine to 30 feet in length, were collected. They were obtained at 2,000-foot
spacings along four shore-parallel lines 1,500, 3,500, 5,500, 7,500 feet offshore along the 18.5-
miles of beach from Phillips Inlet to the Panama City Shipping Channel. Core logs are
presented by the U. S. Army (1995). Sampling water depths ranged from -25 feet NGVD just
seaward of the outer bar to -75 feet NGVD. Additional nearshore surface grab samples were
obtained in 1990 in water depths of -3, -4, and -6 feet NGVD, corresponding to offshore
distances of about 100 feet, 125 feet, and 150 feet, respectively. An acoustic impedance
survey of the offshore was conducted in 1992; results of the survey are given by U. S. Army,
1995. In 1994, multiple nearshore sediment borrow sites were identified on the basis of
additional site-specific investigations (U. S. Army, 1995). For these a total of 58 virbracore and
13 splitspoon cores were taken at 63 locations. Vibracore barrels, 25 feet in length, attained
an average of 93% recovery. Splitspoon sampling was collected at 3-foot intervals to within six
feet of the desired termination depth. Laboratory analyses of selected samples resulted in 376
sieve analyses and three density tests. Selected offshore borrow areas and characteristics for
the coastal reach from the Panama City Shipping Channel west to Phillips Inlet are provided
by Figure 14.
Coastal Planning and Engineering, Inc. (1997) reassessed offshore borrow areas for
Panama City beaches (Figure 15 and Table 4). They found five of the Corps of Engineers (U.
S. Army, 1995) offshore borrow sites (1B, 3B, 5A, 5B, and 5C) to contain sand too fine for
beach nourishment purposes, and recommended not using the sites. They did, however,
identify eight additional sites which may contain suitable borrow material, which increases the
potential total amount of suitable borrow material to 26,847,000 cubic yards. Moreover, for the
existing borrow areas they suggest that additional cores are needed in order to assess
suitablility of the borrow material for beach restoration suitability.
.---2--~ aic ~ ^ t "' "~*--...- -25.... -,s .... ....<..r ....- ~~~/f
9 ..- -.-' C Dsg A" ", 5 .o.r .... r-t,,Uf ... ... r~,, --=
A -' '^ B Do_ F 'l ^--
l -,p,-. .lIi 'I I- t
VU "MGM Sartei Ovew
kue V =ea O ma W
Native Bea h -- 1.99 043 -
Borrow Ares A 1,663.000 1.92 0.83 1.3
Borrow Ar B 438.000 1.95 0.74 1.2
Bwrrow Amr C 216,000 2.12 0.69 1.4
Borow Are 0D 895.000 1.92 0.40 1.3
Borrow Aru E 727,000 2.33 0.60 1.8
Borrow Arm F 759.000 2,41 0.50 2.0
Borrow Area G 2,944,000 2.27 0.70 1.6
Borrow Araa H 974,000 1.94 0.84 1.3
TWa 8.06.000
Contours in Feet
Figure 14. Offshore borrow areas and characteristics for Panama City beaches from the Panama City Shipping Channel
west to Phillips Inlet (after U. S. Army, 1995).
4,.200,000 CY 0 m
0 z
Figure 15. Offshore sand resources for restoration of Panama City beaches (modified after Coastal Planning and
Engineering, Inc., 1997).
Table 4. Information summary for Bay County offshore borrow areas (data
from U. S. Army (1995) and Coastal Planning and Engineering, Inc. (1997)).
_Jf) YARDS) REQUIRED
1A 0.206 1,550,000 1.47 12 Requires final design
1B -- --- 0 Eliminated
H 1.89 1,000,000 1.06 8 Requires final design
2A 2.00 438,000 1.10 2 DEP confirmed
G 1.89 3,000,000 1.19 10 Requires final design
38 2.12 216,000 1.4 0 Eliminated
4A 1.94 895,000 1.18 2 DEP confirmed
F 1.79 4,200,000 1.16 18 Requires final design
D 1.79 1,800,000 1.08 10 Requires final design
C 1.89 2,400,000 1.12 9 Requires final design
B 1.84 5,000,000 1.13 20 Requires final design
A 0.21 6,204,000 1.18 20 Requires final design
5A 2.33 727,000 1.8 0 Eliminated
5B 2.41 759,000 2.0 0 Eliminated
5C 2.27 2,944,000 1.6 0 Eliminated
6 2.00 324,000 1.21 6 DEP confirmed
DEP = Florida Department of Environmental Protection.
See Figure 16 for location of borrow areas.
General Description
Gulf County, located along the central part of the Florida panhandle, lies between Bay
County to the northwest and Franklin County to the east (Figure 16). From the Bay-Gulf County
line, the mainland shoreline extends for about 17 miles in a southeasterly and southerly
direction to a point where it is intersected by the base of St. Joseph Peninsula. The peninsula
is approximately 17 miles in length, trending
north-south, and is connected to the mainland by l' .. i. .
a 3.1 mile east-west trending basal peninsula.
Mainland beaches extend easterly approximately
2.9 miles to Indian Peninsula, a spit separated "
from the mainland by Indian Lagoon. st. Joseph Bay Entrance s "
Tanner (1960b) describes Gulf County "-*
shore energy conditions to be moderate (i.e.,
annual average breaker heights ranging from 0.33 -
to 1.64 feet). Mean range of tide varies from 1.23 ..I.. R
feet at the northwest end of the county to 1.37 *o -. .
feet at the southeast end (Balsillie and others, To Eag.e r .
1987, 1990; Balsillie, 1987). On the basis of its ';g "" Hab
physiography and historical shore behavior, the .90o k .,. s
28.8 miles of Gulf-fronting beach in Gulf County 0
can be divided into three distinct segments. ....,e -'
The first segment, a mainland reach, R.1.0 R 100
extends from the north County line south to Palm""-0 W14n p**
Point (DNR reference monuments R-1 to R-31), C p*a Indn Pass
a distance of 5.7 miles. Photography taken in LF OFEX
1983 shows highway U. S. 98, which parallels this
coastal reach, to lie from 120 to 140 feet east of
the seaward vegetation line and 450 to 550 feet Figure 16. Gulf County coastal
east of the dry beach shoreline. Balsillie (1985) map showing locations of every
notes that the beaches are for the most part tenth DNR reference monument.
accreting. Net longshore transport is to the
southeast (Stapor, 1971, 1973a, 1973b, 1974; Stone and Stapor, 1996).
The second segment occupies St. Joseph Peninsula, a 17-mile reach extending from
St. Joseph Point (2,400 feet north of R-32) south to Cape San Bias (R-116). St. Joseph
Peninsula is a coastal barrier spit of late Holocene age. The spit extends west from the
mainland near the southern end of the county for approximately three miles where it forms
Cape San Bias. The spit then turns north-northwest for a distance of over 17 miles. The north
end of the spit turns northeast and terminates at a point about two miles from the mainland.
St. Joseph Peninsula ranges in width from less than 600 to over 4,600 feet, and is subject to
overwash and breaching at several narrow areas along its length. Primary dunes range in
height from five to as much as 37 feet and average around 16 feet. Beach widths range from
70 to as much as 500 feet (Fischer and others, 1984). Except for about the northern 2.17 miles
(from about R-40 north to R-32 and St. Joseph Point) which is accreting (Balsillie, 1985), St.
Joseph Peninsula is eroding (Stapor, 1971; Tanner, 1975; Balsillie, 1985; Clark, 1993). From
R-40 to R-91 (9.9 miles) the historical erosion rate increases from 0 to -3.75 feet per year; from
R-92 to R-116 at Cape San Bias (4.81 miles) the erosion rate increases from -4.1 to -30.7 feet
per year (Balsillie, 1985). The latter is probably the largest historical long term erosion rate
recorded in Florida. Tanner (1975) notes that the lighthouse located in the vicinity of R-110 (1.1
miles north of Cape San Bias), has been relocated six times to eastern sites since its original
construction. Furthermore, truncation by erosion of east-west trending coastal beach and dune
ridges in the area attests to the degree of erosion. Clark (1993) describes these higher erosion
rates as non-critical on the basis that there are few or little coastal man made
structures/development to be threatened. However, erosion along a 500-foot segment of beach
at Stump Hole (DNR reference monument R-106) threatens county road C30 and is designated
as critical erosion; an emergency rubble mound structure was constructed following Hurricane
Opal along the segment. A longshore drift divide has been identified along the southern one
third of St. Joseph Peninsula (Stapor, 1971, 1973b, 1974; U. S. Army, 1971; Stone and Stapor,
1996). St. Joseph Point is accreting and migrating northward due to erosion north of the divide
and longshore transport of the eroded material to the north. However, progradation of the point
has been described as slight (Tanner, 1975). The majority of eroded material is moving south
of the divide and is accreting in shoals south of Cape San Bias (Tanner, 1960a, 1961; Stapor,
1971, 1973b, 1974; Stauble and Warnke, 1974).
The third, and final, segment extends from Cape San Bias east to Indian Pass (R-116
to R-162), a distance of 8.9 miles. From R-116 at Cape San Bias to R-149 the shoreline is
stable to accreting. Very high historical rates of accretion from 61.4 feet per year at R-119
gradually decreasing to 5.0 feet per year at R-130 (a distance of 2.1 miles) strongly suggest
a significant net eastward sediment transport of Cape San Bias shoal material, controlled
mainly by wave refraction due to shoal configuration. Such a conclusion is strongly supported
by physiographic evidence of backbeach dune ridge formation. Just west of Indian Pass (R-
150 to R-159), a distance of two miles, the shoreline is experiencing noncritical erosion
(Balsillie, 1985; Clark, 1993). Net westward longshore transport, while moderate to slight,
appears to occur from R-159 just west of Indian Pass to about R-145, a shoreline reach of
about three miles. Hence, a longshore transport node exists due to the convergent transport
directions between about R-135 and R-148. The immediate closure of Money Bayou at R-141
following opening by hurricane Kate attests to the overpowering influence of alongshore or
onshore sediment transport processes relative to inlet hydrodynamics, and supports the
existence of a transport node in the area.
Inlet Sand Resources
St. Joseph Point Channel: There exists a tidal entrance between St. Joseph Peninsula and
the mainland which connects the Gulf of Mexico with St. Joseph Bay. This tidal entrance is a
little less than two miles wide and has a navigation channel immediately adjacent to the north
end of St. Joseph Peninsula. The entrance has been the historical navigation route to Port St.
Joe. Erosion has prevailed along most of St. Joseph Peninsula, while accretion has occurred
at the northern tip due to a predominant northward longshore transport. The northern tip of the
peninsula lengthened nearly 4,000 feet between 1875 and 1970. Because considerable
deposition occurs at the north end of the peninsula, shoaling in the navigation channel is
significant. The ebb shoals of St. Joseph Bay store an estimated 145 million cubic yards of
sediment (Hine and others, 1986).
In 1913 and 1914, 456,000 cubic yards of sand were dredged from the entrance channel
and disposed in an open water area. An initial 27 foot deep Federal navigation project was
authorized in 1937, and about 1,234,000 cubic yards of material were dredged from the
entrance channel and disposed in an open water site between 1938 and 1942. In 1945, the
channel was authorized to a depth of 32 feet and about 2,442,000 cubic yards of material were
dredged and disposed in open water between 1948 and 1953. In 1954, the channel was
authorized to a depth of 37 feet, whence between 1955 and 1970, approximately 6,797,000
cubic yards were dredged and disposed in two open water spoil areas in the Gulf of Mexico.
In 1970 and 1973, nearly 1,150,000 cubic yards of sand were removed from the entrance
channel and a silting basin and placed in an upland dike area on the north end of St. Joseph
Peninsula. In 1981, nearly 332,000 cubic yards of material were removed from the entrance
channel, the silting basin, the north channel and harbor channel and disposed in an open water
area in St. Joseph Bay. In 1985, the first inlet sand transfer operation was conducted with the
excavation of approximately 300,000 cubic yards of sand placed along the Gulf beach of St.
Joseph Peninsula. (Balsillie and others, 1990).
Indian Pass: Separating Indian Peninsula in Gulf County and St. Vincent Island in Franklin
County, Indian Pass is a natural tidal inlet connecting the Gulf of Mexico with both Indian
Lagoon and St. Vincent Sound. Indian Pass is the westernmost coastal barrier inlet in the
Apalachicola estuarine system. Historically, the inlet has never been strategically important for
either commercial or recreational navigation, although depths are sufficient. Given the lack of
navigation interest, the inlet was not adequately surveyed in the 1800's. Recent computations
suggest the outer shoal storage of sand to be approximately 2.4 million cubic yards (Walton
and Dean, 1976). Historically stable, the general position of the shorelines have changed little
since the 1874 government survey. Stapor (1971) suggested that there is little net exchange
of sediment between Cape San Bias and West Pass because of the relatively balanced sand
budget adjacent to the inlet and because of the relative stability of the inlet shorelines over time.
Westward along the Gulf beach of Indian Peninsula, the shoreline is eroding for over 2.5 miles.
Two miles east of Indian Pass, St. Vincent Island is eroding for over three miles of its length.
(Balsillie and others, 1990).
Offshore Sand Resources
Stewart and Gorsline (1962) studied St. Joseph Bay and offshore areas. Eighty
subaqueous surface sediment samples were collected of which half were located in St. Joseph
Bay and half in offshore waters. Clean quartz and biological carbonates comprise the bulk of
sediments. Offshore sediments were collected up to from two to seven nautical miles offshore
(water depths of from 35 to 40 feet). Sampling site and mean grain size information are plotted
in Figure 17. Subaqueous bathymetry, sediment types, standard deviation, chemical analyses,
including percent carbonate and organic carbon and nitrogen content, sedimentation trends,
etc., are discussed in this account.
Lader (1974) conducted granulometric, electron microscopy, and heavy mineral studies
of littoral sediments (48 samples) from Cape San Bias to Indian Pass.
Stauble and Warnke (1974) also investigated subaqueous surface sediments off the
western shores of southern St. Joseph Peninsula. However, their study was a part of a more
extensive study south and east of Cape San Bias. In addition, the east-west trending coastal
reach east of Cape San Bias received considerable attention from other researchers. Because
this reach is a westward continuation of processes related to east-west trending coastal barriers
of Franklin County, details are presented in the section on Franklin County.
Figure 17. Sampling sites and mean grain size isolines
(large type in phi units, small type in mm) from Stewart
and Gorsline (1962).
General Description
Franklin County is located along the eastern section of Florida's northwest panhandle
coast, between Indian Pass and Gulf County to the west and the north bank of Ochlockonee
Bay and Wakulla County to the east (Figures 18a and 18b). Franklin County has 54.6 miles
of gulf frontage located on ., i i....
a series of coastal barrier .
complexes in Franklin
County which, from west to
east, are: St. Vincent
Island, St. George Island, A, .... ... Pas
and Dog Island. St. F '"
George Island has been ,,,. **'
artificially segmented by a MM
navigation inlet, known as L,,. St Oorge sland .
Bob Sikes Cut or St. Wet Pa ss.O.. *..g t.l.n
George Island Channel to R-Io SD Bob Sikes Cut
the west of which lies Little A,
St. George Island. Dog ' G F
.MM c=p st. GeOrge GULF OF MEXICO
Island lies to the northeast
of St. George Island. East
of Dog Island is a barrier Figure 18a. Western Franklin County coastal map
spit which trends in an showing locations of every tenth DNR reference
east-west orientation, monument.
paralleling the mainland shore and creating Alligator Harbor; it is connected to the mainland at
its eastern end. The coastal barrier islands are separated from the mainland by three
interconnecting water bodies, St. Vincent Sound, Apalachicola Bay and St. George Sound.
Beaches along the barrier islands are relatively flat and average about 180 feet in width
(Fischer and others, 1984). However, beach widths range from 800 feet to less than 20 feet.
The beaches are backed by dunes with elevations ranging generally 10 to 15 feet above mean
sea level (U.S. Army, 1971), with some dunes attaining elevations as high as 31 feet (Fischer
and others, 1984). The Franklin County mainland coast is composed mostly of east-west
trending Pleistocene barrier ridges which form bluffs at many locations along the sound. In the
eastern part of the country, limestone lies at or near the surface leading to the formation of
sinks, caves and other karst features due to solution activity.
Tanner (1960a) describes Franklin County as having a low wave energy shoreline (i.e.,
average annual breaking wave heights less than 0.33 feet). The mean range of tide varies
from 1.42 feet at the western end of the county to 2.24 feet at the eastern end (Balsillie and
others, 1987, 1990; Balsillie, 1987).
Existing reports (U.S. Army, 1971; Stapor, 1971, 1974; Tanner, 1975; Stone and Stapor,
1996) indicate that coastal Franklin County has historically undergone moderate and systematic
shifts and migration in i|| H
cells. Such moderate
changes are related to a T All .|.|iga tor 1A1i|at
characteristic low wave |-oo
energy climate (Tanner, li.....
1960a, Gorsline, 1966). C p.
Otvos (1985) discusses | |-
Franklin County barrier
island genesis. Clark
(1993) notes that 18.3 ." eP0
miles of beach are ,. .- .o
experiencing erosion (16.3 E-st Paeo '"'g1
miles non-critically, and
2.0 miles critically).
St Vincent Island, .. -
the westernmost barrier V-ia
island, is approximately
7.5 miles long, triangular Figure 18b. Eastern Franklin County coastal map
shaped and characterized showing locations of every tenth DNR reference
by a unique complex of monument.
multiple beach ridges trending generally in a southeasterly direction. This beach ridge plain is
almost four miles wide and reportedly contains 12 beach ridge sets with approximately 180
individual sand ridges (Stapor, 1973a, Campbell, 1986). St. Vincent Island is separated from
adjacent St. George Island by West Pass, a natural inlet less than one-half mile wide. Of the
7.5 miles of Gulf-fronting shoreline of St. Vincent Island, Clark (1993) reports 3.2 miles of the
center portion of the island to be experiencing non-critical erosion.
Little St George Island and St. George Island, combined, are approximately 29 miles
long (R-1 at West Pass east to R-148 at East Pass) and range from about 1,100 feet to slightly
over a mile in width. The western 3.7 miles of Little St. George Island differs in character from
the remainder of the barrier. From West Pass to Cape St. George, Little St. George Island has
the same southeasterly orientation as adjacent St. Vincent Island and is composed of
approximately 35 parallel barrier ridges similar to those of the St. Vincent beach ridge plain.
This section of the island was once separated from the remainder of St. George Island by a
natural inlet, forming Little St. George Island. The two islands merged in the late 1800's to form
one continuous feature (although the inlet opened briefly again n the 1920's). At Cape St.
George, the island changes orientation and trends in a northeasterly direction for the remainder
of its length. With the exception of an older, more complex segment near its northeast end,
this portion of St. George Island is a rather simple, narrow barrier with numerous breaches and
washovers. There is a small jettied inlet called Bob Sikes Cut located about 10.5 miles east
of West Pass which was constructed in 1954 to allow navigation access. The northeast end
of St. George Island is bordered by a discontinuous belt of tidal marshes and the shallow
waters offshore display numerous shoals and sand waves. Near West Pass a 0.4 mile
segment of beach (R-3 to R-5) is reported to be undergoing non-critical erosion, as is a 1.3 mile
segment of Cape St. George (R-17 to R-24). The shoreline adjacent to Bob Sikes Cut, located
between DNR reference monument, R-34 and R-69, is experiencing noncritical erosion
(approximately 3.2 miles to southwest, and 3.3 miles to the northeast). The eastern tip of St.
George Island (0.5 miles) is also undergoing non-critical erosion. (Clark, 1993).
Dog Island is 6.9 miles long (R-150 to R-193) and irregularly shaped, with a narrow
western segment and a broader eastern portion. The shape is typical of what is termed a
"drumstick" barrier (Hayes, 1979), in which littoral transport is bidirectional, with the dominant
longshore transport occurring in the direction of the narrow end of the island and opposing
longshore transport near the broad end. This sediment transport reversal is due to offshore
sand shoals which refract the incoming waves (Davis, 1989). Tanner (1990) has located the
drift divide near the middle of the eastern portion of the island, and has correlated energy
expenditures associated with longshore transport based on the kurtosis of granulometric
parameters. The western end of Dog Island displays a few hooked, sand ridges which
indicates westerly growth. The eastern end is more complex, consisting of at least four sets
of hooked spits, indicating a northeasterly growth. There are two narrow (less than 500 feet)
segments located in the western portion of the island which are susceptible to breaching. The
broadest portion of Dog Island near the northeastern end is approximately 4,300 feet wide.
Non-critical erosion (Clark, 1993) is occurring along 2.4 miles of southwestern Dog Island (R-
157 to R-170), and along 0.7 miles of northeastern Dog Island (R-180 to R-184).
There is a small beach on the mainland just west of Carrabelle which has formed
landward of East Pass in the opening between Dog and St. George Islands.
The eastern part of Franklin County is a mainland peninsula, known as St. James
Island, which is separated from Wakulla County to the north by Ochlockonee Bay, the receiving
body of water of the Ochlockonee River. The eastern end of the peninsula extends in a north-
south direction for a distance of 3.4 miles from Bald Point to Lighthouse Point. From
Lighthouse Point, a recent (Holocene) barrier spit extends almost five miles to the west which
is separated from the mainland by Alligator Harbor. This spit, known as Alligator Peninsula,
is growing in a westerly direction. The mainland coast between Alligator Point and Dog Island
does not exhibit much beach growth due to the presence of numerous shoals, sand waves and
a prominent sand bar over 5 miles in length paralleling the shoreline in St. George Sound.
Along the 9.3-mile arcuate shoreline from Peninsula Point to Ochlockonee Bay, Clark (1993)
reports three erosion areas. Warnke (1967) reported on such erosion during the mid-1960's.
At Peninsula Point (R-194 to R-196) there is a 0.4 mile segment of non-critical erosion.
However, two areas of critical erosion occur along the 1.1 mile segment of Southwest Cape (R-
210 to R-216), and along the 0.9 mile reach of Lighthouse Point (R-220 to R-225). An adjacent
0.9 mile segment at Lighthouse Point (R-225 to R-229) has non-critical erosion.
Inlet Sand Resources
Indian Pass: Indian Pass is shared by both Franklin and Gulf Counties, and has been
presented in the Gulf County discussion.
West Pass: West Pass is a natural inlet between Little St. George Island and St. Vincent
Island connecting the Gulf of Mexico and Apalachicola Bay. Between 1852 and the early
1900s, the northwest end of Little St. George Island was separated from Little St. George
Island. New Inlet, another pass located to the east of Cape St. George, historically separated
Little St. George Island from St. George Island after a hurricane breached an opening in 1837.
The pass is thought to have closed between 1896 and 1902, then reopened and closed again
during the period 1927-1929. West Pass, due to its relatively deep natural channel, has been
the historic navigable entrance into Apalachicola Bay.
Because West Pass has historically remained a deep navigable inlet, little dredging has
been required. Between 1900 and 1948, nearly 466,000 cubic yards of material were dredged
and disposed in an open water site (Hine and others, 1986). The location of the West Pass
channel, being somewhat inconvenient to Apalachicola, was a factor prompting local interests
to initiate a federal navigation project which created Bob Sikes Cut that now divides St. George
Island. There is a vast quantity of sand (estimated at greater than 51 million cubic yards)
stored in the lunate bar located east and south of West Pass. Accretion has occurred along
St. Vincent Island and Little St. George Island immediately adjacent to West Pass within the
influence of the inlet shoals. The Gulf shoreline along St. Vincent Island for 3.2 miles west of
the West Pass shoals and a 0.4-mile segment at the west end of Little St. George Island are
non-critically eroding (Clark, 1993). Further east, a 1.3 mile segment around Cape St. George
is eroding.
Bob Sike's Cut: Also known as St. George Island Channel, Bob Sike's Cut is an artificial
navigation channel across St. George Island connecting the Gulf of Mexico and Apalachicola
Bay. The inlet was originally dredged in 1954 by local interests, but was taken over as a federal
responsibility through the River and Harbor Act of September 3, 1954. Bob Sikes Cut has
become the primary route for commerce to Apalachicola, a function which had historically been
provided by West Pass.
In 1956, the Corps of Engineers constructed two granite boulder jetties spaced 400 feet
apart and extending 500 feet into the Gulf to the -10 foot contour. The northeast jetty has a
length of 800 feet and the southwest jetty has a length of 1,000 feet. The inlet's interior
shorelines have experienced significant recession associated with inlet shoaling and
maintenance dredging activity. A 1970 study concluded that the annual erosion of the inlet
"side walls" to be approximately 47 percent of the total average yearly maintenance dredging
(University of Florida, 1970; Zeh, 1980).
Shoaling has historically been a problem in the inlet channel, as well as in the gulf and
bay channel segments adjacent to the inlet. The Federal navigation project's initial dredging
totaled 77,749 cubic yards in 1956 and 83,459 cubic yards in 1957. Channel maintenance
dredging since 1957 has totalled 1,115,554 cubic yards for an annual quantity of almost 40,000
cubic yards. An open water site in Apalachicola Bay immediately west of the channel was used
for disposal of maintenance dredging material during the 1960's and early 1970's. Inlet sand
transfer to the beach, west of the entrance jetties, was conducted in the late 1970's. Eroded
shores east and west of the inlet have been nourished with dredge material during the 1980's
to prevent and repair breaching between the jetties and the gulf shoreline. The jetties were
breached by the storm surge of hurricane Elena in September, 1985 (Clark, 1986).
The ebb tidal shoal has been estimated to store approximately 600,000 cubic yards of
sand (University of Florida, 1970). Tidal influence of the inlet on Apalachicola Bay was
investigated and determined to be relatively minor (Mehta and Zeh, 1980). Annual net
longshore sand transport along St. George Island has been estimated to be from 127,000 to
175,000 cubic yards to the west (Stapor, 1973a; Walton, 1973). The Gulf shoreline for over
three miles to both the east and west of the inlet is eroding. Inlet sand transfer is needed to
the beach west of the inlet.
East Pass: East Pass, located between St. George Island and Dog Island, is a wide natural
tidal entrance connecting the Gulf of Mexico with St. George Sound. East Pass has provided
a lesser used eastern navigation route to Apalachicola, but is the main navigation route to
Carrabelle. During the period 1885-1970, East Pass decreased in width from about 2.5 to less
than two miles due to lengthening of the east end of St. George Island and the west end of Dog
Shoals exterior to the pass have been estimated to contain over 54 million cubic yards
of material (Hine and others, 1986). Because East Pass is a wide stable inlet with a natural
20 foot deep channel, maintenance has not been a problem. Between 1905 and 1943, a 27
foot deep federally authorized navigation channel was maintained with approximately 1,042,600
cubic yards of material dredged and disposed in open water in the Gulf of Mexico (Hine and
others, 1986). After 1943, maintenance of the 27 foot channel depth was discontinued to
match the controlling 12 foot depth of the Gulf Intracoastal Waterway. There is a general trend
of erosion along the western half of the Dog Island shoreline fronting the gulf which has been
calculated to be about 107,200 cubic yards per year during the period 1858 to 1970. Significant
accretion has occurred at the west end of Dog Island at the rate of about 91,600 cubic yards
per year. Accretion of the west end of Dog Island has been about 2,300 feet during this past
century. Similarly, the east end of St. George Island has accreted into East Pass at the rate
of about 99,400 cubic yards per year (Stapor, 1973a). The northeast point of St. George Island
has migrated about 2,500 feet during the past century.
Ochlockonee Bay Entrance: Ochlockonee Bay Entrance marks the terminus of the
Ochlockonee River which drains over 1,550 square miles in Florida and Georgia. The large
natural inlet separates Mashes Sands to the north from the St. James Island (Bald Point to
Lighthouse Point) to the south. Mashes Sands has been described as a chenier type beach
system (Tanner, 1961). Beach sediments of St. James Island and Mashes Sands are derived
from the Ochlockonee River drainage basin. Tidal hydrodynamics of this entrance have not
been previously described; however, the mean tide range of 2.0 feet and the diurnal tide range
of 2.7 feet are the largest of any of the northwest Florida inlets (National Ocean Service, 1988).
Even though natural depths between -10 to -15 feet penetrate well into Ochlockonee Bay, no
port was ever developed and navigation has historically been limited to small commercial and
recreational craft. A vast, but unknown quantity of sand exists in the ebb tidal shoals. Except
for minor dredging adjacent to some residential canals on the north shore of Ochlockonee Bay,
navigation dredging in the entrance does not appear to have been conducted.
Apalachicola River: The Apalachicola River has and continues to be a shipping route. The
navigation channel (100 feet wide and 9 feet deep) is maintained by the U. S. Army Corps of
Engineers). Maintenance dredging has resulted in the creation of more than 130 upland and
bank-side spoil sites, some of which are of significant size. An interagency team (U. S. Army
Corps of Engineers, Northwest Florida Water Management District, U. S. Department of the
Interior, Florida Department of Environmental Protection (Office of Beaches and Coastal
Systems)) has been convened to investigate utilizing this spoil material for various purposes,
potentially including its use for beach nourishment. Investigations are continuing (Smith and
others, 1991; KBN Engineering and Applied Sciences, Inc., 1995).
Offshore Sand Resources
A considerable amount of nearshore and offshore investigation has been conducted
from Cape San Bias (Gulf County) east to the vicinity of the Ochlockonee River entrance
(Franklin County).
Tanner (1959) directed a
series of sedimentologic studies
for the area including beach and -I-E ..- .. A
barrier island studies (e.g., F L R
Brenneman, 1957; Brenneman
and Tanner, 1958; Stapor, 1973a, TALLAHASSEE
1973b; Von Drehle, 1973;
Emmerling, 1975; Campbell, APALACHICOLA
1979; Spicola, 1984; Rizk, 1985; RIVER
Schade, 1985) and offshore P "AnA r
sedimentologic studies (e.g.,
Vause, 1957; Milton, 1958;
Mullins, 1959). Additional studies ALACE
and Tanner and others, 1961). S 1T \,H POINT
Studies (Figure 19) were A ALACH U DO L'-
conducted up to 12 miles CAPE /T "MY
offshore, where three main types ."JL PW
of bottom conditions were found: s / ~, st acoe o 25
St VINCENT I' STLGEORGE 1. -. .-
karstified wave-cut limestone, M; 'ILES
shell hash, and quartz sand. In
general, quartz sand grain size Figure 19. Location of Gulf County and Franklin County
increases in a seaward direction, shoal and detailed bottom studies.
as does the quantity of shell
hash. Overall, the veneer of
quartz sand/shell hash is thin. However, three large shoals were found and studied. These are
located just offshore and to the south of Cape San Bias, Cape St. George, and Alligator Spit.
Vause (1957) investigated subaqueous surface conditions some six nautical miles
offshore of the coastal reach extending from central St. George Island east to Alligator Spit.
Sampling station (102) locations and median grain size are plotted in Figure 20. Granulometric
parameters, accumulative probability plots, percent carbonate, etc. are detailed by the author.
Unconsolidated sand thins in the seaward direction. Several miles offshore sediments
overlying the limestone are, in many places, only an inch or two thick. Hardbottoms were
commonly encountered. Four bottom types were identified: 1) a clean white quartz sand,
found nearshore, 2) a slightly coarser white sand containing many shell fragments and dark-
colored grains, found further seaward, 3) a brown sand with a high carbonate content
containing very coarse sand and granule gravel, found in deeper water at the end of the
traverses, commonly associated with rock outcrops, and 4) a fine-grained sand that formed
a very flat bottom at many of the stations in the eastern portion of the study area.
Mullins (1959) conducted a sedimentological investigation of shoals lying offshore of the
western portion of St. George Island and Cape St. George, extending some 12 miles offshore
to water depths of 72 feet. A total of 38 sampling sites covered an area of 45 square miles.
Median grain size and sample site locations are provided by Figure 21. The shoal is comprised
of a series of ridges and troughs. Ridge sediments were finer, better sorted, and had greater
carbonate content than adjacent trough sediments. Sediments, in general, ranged from clean
quartz sand to iron-stained, silty sediment. Carbonate content ranged from 1.4 to 64.8%.
Granulometric parameters, cumulative probability plots, carbonate content, and heavy mineral
content details are provided in this account.
Figure 20. Sampling locations and median grain size of sediments offshore of
St. George Island to Alligator Spit from the study of Vause (1957).
In addition to the study of surface sediments of Apalachicola Bay, Kofoed (1961) and
Kofoed and Gorsline (1963) investigated surface sediments offshore and south of the coastal
reach from Cape San Bias to Cape St. George. Forty-eight sites were sampled up to 12 miles
offshore to water depths of about 75 feet. Surface sediment types and sample site locations
are illustrated in Figure 22. Granulometric parameters (mean, standard deviation), percent
calcium carbonate, percent organic carbon, etc., were statistically treated, and Kofoed (1961)
provides tabulations of weight percent for sand, gravel, carbonate, silt fractions, and physical
description for each sample.
Schnable (1966) and Schnable and Goodell (1968) report on sedimentologic conditions
of the Apalachicola area. It is reported that subsequently filled drowned river valleys have been
found, which contain significant sand-sized material.
Neurauter's (1979) side-scan/seismic bedform study covered an area off of Cape San
Bias east into Apalachee Bay (see Figure 3). Zone D1 of Figure 3 lies offshore of Cape San
Bias east to the western end of St. George Island in water depths of from 43 to 131 feet.
Bedforms in Zone D1 are described as giant-scale features with an average relief of from 11
to 16 feet and wave lengths from 1,440 to 2,700 feet. Some 54 giant-scale features were
identified along legs 31 and 32. A field of giant-scale bedforms was also identified along the
nearshore part of leg 33. Zone C1, lying just east of Zone D1 offshore of the western portion
of St. George Island, is characterized by small-scale, low-relief bedform features. Leg 25 of
Zone B which extends from Zone C1 east into Apalachee Bay, is largely characterized by low-
relief bedforms, except for one giant-scale feature. For additional information, the reader is
encouraged to consult Neurauter's text and detailed plates that could not, because of size, be
reproduced here.
Arthur and others (1985) ISL A
have corroborated identification of
offshore shoals off of Franklin
County. Dog Island Reef lies -- -
parallel to the coast between Dog MILIMETERS
Island and Alligator Spit. South iS
Shoal lies south of Alligator Spit, 0 -.o
extending offshore some five
miles. Ochlockonee Shoal lies .10 -20
approximately eight miles TR]
southeast of the Ochlockonee .20-3o
River entrance. These shoals are
believed to be drowned barrier
islands (Schnable and Goodell,
1968). Shoals lying south of
Cape St. George and Cape San 290* 40-50 -O29
Bias are described as extending
about ten miles into the Gulf and .5067
are characterized by broad
irregular ridges and troughs.
Stapor (1971) has further
investigated erosional/
depositional changes of the Cape Sampling Sites
St. George shoal, nearshore
areas off West Pass, and the
Cape San Bias shoal, and o z, .mies
conducted heavy mineral studies 8o0'
(Stapor, 1973b). GULF OF EOco MC
Stauble and Warnke Figure 21. Sample site locations and median grain size of
(1974) investigated bathymetric subaqueous surface sediments for Cape St George shoal
changes and granulometry of the (from Mullins, 1959).
Cape San Bias shoal. The study
included an area up to 7.5 miles south of and 8 miles west of Cape San Bias. Bathymetric
changes for a 30-year period (1940 to 1970) showed that unconsolidated sediments were, in
places, redistributed in the vertical direction by as much as 24 feet (i.e., 8 feet of deposition in
some places, 16 feet of erosion in others). They also collected 144 surface sediment samples.
Mean grain size and standard deviation are presented as isoline plots, texture is discussed in
the text. Subaqueous surface sediment types are provided in Figure 23.
Ware and Kirkpatrick (1981) conducted a shallow drilling program on Cape St. George
shoal. Only 5 out of the 95 total samples contained heavy mineral content greater than one per
Isphording (1985) compiled the results of a sedimentological study of Apalachicola Bay
and estuary.
Figure 22. Surface sediment types and sample site locations for the
investigation reported by Kofoed (1961) and Kofoed and Gorsline (1963) (after
Kofoed, 1961).
Some seismic tracklines through the area offshore of St. George Island are presented
by Donoghue (1993a), and analyzed by Donoghue (1991, 1993b) providing details of paleo-
channel sedimentation (Figure 24). Donoghue and Tanner (1992) and Tanner and Donoghue
(1993) discuss sediment delivery of the Apalachicola River.
Reconnaissance of areas off the mouth of the Ochlockonee River entrance and to the
north offshore of Mashes Sands, also reveals significant shoals of quartz sand. A number of
jet-probes (11) indicates sediment thicknesses exceeding an average of 9.2 feet, and ranging
from 0.5-foot to greater than 23 feet (L. J. Ladner, J. M. Lloyd, J. H. Balsillie, 1996,
unpublished Florida Geological Survey field data).
.___ _~
Figure 23. Subaqueous surface sediment type and sampling sites of Stauble and
Warnke (1974).
Figure 24. Seismic track lines and study area of Donoghue, 1991, 1993a,
1993b (after Donoghue, 1993b).
From Anclote Key to the north to Cape Romano to the south, the barrier islands of the
Lower Gulf Coast constitute a near continuous chain extending 183 miles. With few exceptions
(e.g., Cedar Keys), barrier islands have not formed to the north of Anclote Key where the coast
is characterized as a nonbarrier, open marine, marsh dominated zone, and barriers have not
formed in the zone due to the lack of sand and low wave energy (Tanner, 1960; Hutton and
others, 1984; Hine and Belknap, 1986; Hine and others, 1986). While there is one sound, one
mainland reach, and what appears to be an upland coast of reliction, the Lower Gulf Coast is
characterized by 41 inlets which is indicative of the number of barrier islands. (Balsillie and
Clark, 1992).
Unlike the Northwest Panhandle Gulf Coast, the Lower Gulf has had a plethora of
projects where sand has been placed on the beaches, paralleling development pressures.
While there has been a history of offshore spoiling of dredge material, there have been since
the late 1950's some 98 beach fill projects involving approximately 32,026,000 cubic yards of
material. Of these there have been 71 inlet sand transfer projects involving some 17,626,400
cubic yards of sand, 20 projects using offshore sand sources for some 11,931,250 cubic yards
of material, eight projects using inland borrow sand (trucked upland sand or dredged material
from the Intracoastal Waterway) for about 1,019,000 cubic yards of material, and ten
emergency fill projects using about 1,549,000 cubic yards of material.
All of Florida's coasts are subject to extreme event erosion. For the Lower Gulf Coast
recent notable extreme climatic impacts occurred from Hurricane Donna in 1960, No Name
Storm in 1982, Hurricane Elena in 1985, Hurricane Andrew in 1992, the March 13, 1993 "Storm
of the Century", and Tropical Storm Josephine on October 7, 1996. The ensuing account for
the Lower Gulf Coast does not refer to extreme event impacts and their consequences.
Information, however, is available. Some references include Tanner (1961), U. S. Army (1964),
Clark (1982, 1985), Trescott (1983), Balsillie (1985a, 1985b, 1986), Bodge and Kriebel (1985),
Kriebel (1987), Davis and Andronaco (1987), Clark and West (1996).
One of the earliest and most elucidating studies of surface sediment characteristics of
the west-central inner shelf of Florida's Gulf of Mexico was conducted by Gould and Stewart
(1955). Their results, presented in Figure 25, indicate an innermost zone with an average width
of about 20 miles, whose sediments are composed chiefly of quartz sand, with phosphate
grains locally abundant, and varying amounts of shell hash. The next seaward zone, lying from
about 30 to 50 miles offshore, contains more shell than quartz sand. Bathymetry within this
part of shelf exhibits an average slope of 2.6 feet per mile. Texturally, both zones are
characterized by fine- to medium-grained sand sized material. The authors point out, however,
that these unconsolidated sediments do not form a continuous cover over the subaqueous
topography. They report widespread occurrences of limestone in these offshore areas.
Although their sampling effort included 2,484 samples, this results in an average sampling
density of but one sample for every 9 square miles, and they state "... it is impossible to show
boundaries between bare rock exposures and unconsolidated sediments." They also note "...
unconsolidated sediments in many places form only a thin veneer on the bedrock surface."
Brooks and others (in preparation, in manuscript) note that the nearshore quartz sand belt
is really a patchy distribution, in some places dominated by quartz sand, but in others by
9 n
Figure 25. Bottom sediment characteristics of offshore west-central Florida (from Gould and Stewart, 1955).
Figure 26a. Fishing ground locations of Moe (1963); see Table 5a for descriptions.
carbonate sands.
Moe's (1963) fishing ground survey, provides for the description of offshore bottom
conditions. Locations are given in Figures 26a and 26b; descriptions are provided in Tables
5a and 5b. Note that only those areas located in water depths of 60 feet or less are considered
here. The reader is referred to Moe's work for areas located in deeper water.
Neurauter's (1979) work, introduced earlier, includes several zones (A, B, C, and E)
lying offshore of the Lower Gulf Coast (Figure 3). Zone A is solely considered here because
it encompasses offshore areas nearest the coast in water depths less than 66 feet. The zone
extends from Sanibel Island north to the Suwanee River. It needs to be recognized that less
than 30% of Zone A was covered by geophysical transects. Of those areas covered, 88 areas
of giant- to large-scale bedforms were identified. Of these, 14 were well-defined and of an
extent to be termed "major fields", and 13 were located in water depths of 33 feet or less.
Sixteen areas of low-relief bedforms, and 3 fields of small-scale features were also identified.
Neurauter presented a bedfrom lineation plot identified from U-2 imagery (Figure 27) for the
coastal reach from Indian Rock Beach (Pinellas County) south to the vicinity of Big Sarasota
Pass (Sarasota County). Details of bedform fields are described in individual county accounts.
More detailed information (including information for deeper water Zones B, C, and E) is
provided in Neurauter's text and plates that are too large to be reproduced in this work.
Bodge and Rosen (1988) wrote an account presenting a survey of existing knowledge
of potential offshore and inlet-related sand sources for beach restoration and renourishment
along the Lower Gulf Coast. Their findings shall be discussed for each appropriate county.
Doyle (1983) conducted a seismic and surface sediment sampling study off the Lower
Gulf Coast from the vicinity of Honeymoon Island south to the Ten Thousand Islands (Figures
28a and 28b). He found that the inner reaches of the west Florida shelf encompass a major
compositional transition from over 90% carbonate sediments (mostly shell hash) offshore, to
Figure 26b. Fishing ground locations of Moe (1963); see Table 5b for descriptions.
Table 5a. Subaqueous bottom description for fishing grounds (from Moe, 1963).
Area Local Name North Depth Bottom Composition and Topography
West North (feet)
__Longitude Latitude
PA-K Off North Pass 83 06' 280 23' 36 Area of 3 square miles; flat sand and shell bottom;
numerous exposed rocks with high coral or
vegetative growth; 12-foot relief in some areas.
PA-L West of South 83 02' 280 11' 30 to 35 Generally flat and rough; few areas of strong relief;
Pass large flat-topped rocks with crevices and ledges.
PA-N 83" 13' 28' 08' 57 to 70 Generally flat sand and shell bottom with rocky areas
of up to 14 feet in relief scattered through the area.
PA-O Hotel Range 830 04' 28" 03' 40 to 45 Rocky bottom 2- to 3-foot relief; sharp ledges and
crevices; extensive invertebrate and vegetative
growth; some shell.
PA-P 830 02' 27 58' 36 to 42 Oblong area 3 miles long; scattered rock on sand and
to shell bottom; six areas with ledges of 9 feet in the
28 01' southern section.
PA-R 820 57' 27" 56' 25 to 30 Two square mile area; flat bottom; scattered low rock
with coral growths.
PA-S 83' 16' 27 42' 50 to 100 Southern portion has a rolling sand and shell bottom
to to with scattered rock and sponges; northem portion
830 28' 270 53' has flat sand and shell bottom with rocky areas of
moderate relief; numerous ledges and crevices.
PA-T 82* 58' 270 47' 50 to 54 Small artificial reef built on surrounding rock and mud
to bottom; dropped in 1959; mild relief.
830 04'
PA-U 82' 59' 27' 40' 36 to 45 Rocky bottom; relief of several feet; rocks scattered
over sand and shell bottom with extensive vegetation.
CH-A Dunedin 82' 55' 28' 03' 28 to 32 Flat sand and shell with a small area of rock, 4-foot
Wreckage Drop relief; auto bodies and other junk dropped in 1960.
CH-B The Wreck 83 08' 27' 57' 30 to 60 Flat sand bottom with exposed rock in the vicinity;
wreck of old dredging barge sunk about 1920.
CH-C Times Square 82 55' 27 41' 35 Sand and flat rock of low relief; additional rock in the
vicinity; wreck of an old barge supplemented with
auto bodies and other junk; most drops made about
CH-D Eqmont 82' 56' 27' 36' 6 to 90 Large and varied area; channel depth averages 25
Channel feet; one rocky depression 90 feet in depth at north
____ __ end of Egmont Key; bottom mostly sand and mud.
Table 5b. Subaqueous bottom description for fishing grounds (from Moe, 1963).
Area Local Name est North eeth Bottom Composition and Topography
a mt North (feet)
_____ Longitude Latitude __
CO-B The Wreck 82' 51' 26 46' 60 Shipwreck on a sand and shell bottom with a few
scattered low rocks. Large wreck, buoyed.
PA-E 9 Fathom Gully, 82 49' 27- 19' 54 Rock ledges with 5- and 6-foot relief on sand and shell
Barracuda Hole bottom; the ledges are parallel to the coast and form
a small gully about 1 mile in length.
PA-I 820 16' 260 23' 30 to 54 Rolling bottom of sand and shell; few sand hills 10 feet
to to in height. Scattered rock occurs in the depressions
820 25' 260 29' formed by the sand hills. A few 6- to 10-foot rock
ledges are in the area.
PA-J The Mud Hole 82' 01' 26" 11' 60 A fresh water spring has created a cavity in the base
rock 25 to 30 feet below the level of the bottom.
There is a boil of discolored water at this location.
The cavity has steep rock sides.
PA-K 82' 08' 26 05' 40 to 60 Irregular sand and shell bottom; many holes and dips
to to with rock ledges and scattered rock. The eastern side
822 17' 26' 17' has large patches of flat rock 2 to 3 feet above the
bottom level; considerable sponge and coral growth.
CH-A 82" 50' 27T 34' 20 to 25 Hard bottom of sand and shell; flat with sparse grass
CH-B Southwest Pass 82" 40' 270 30' 25 to 30 Hard sand and shell bottom with scattered grassy
to to areas.
820 55' 27 38'
CH-C 82' 53' 270 17' 50 Bottom of sand and shell surrounding a patch of flat
to rock 6 miles long and one mile wide. Many deep
27 22' crevices and caves.
CH-D 82" 41' 27r 12' 30 Small, high rock formation on a bottom of sand and
CH-E The Ice Box, 82 41' 27 10' 50 Two areas of extensive rock bottom; one 50 feet, 220'
The Barracuda to to from Sarasota Pass and one 260 from Sarasota
Hole 82' 47 27' 16' Pass. the rock area extends between these two
locations,; rock is usually found in gullys.
CH-F 820 41' 27" 05' 60 Old shipwreck, hard to find; relief of wreck not high;
surrounding bottom of sand, shell and sparse rock.
CH-I Off Little 82* 21' 26 50' 22 to 55 Sand and shell bottom with scattered areas of rock; 3-
Gasparilla Pass to 7-foot relief considerable invertebrate growth.
CH-J Boca Grande 820 16' 26 42' 40 to 80 Main pass to Charlotte Harbor; deep with strong tidal
Pass flow; hard bottom of sand and rock.
CH-K West of Redfish 82' 21' 26* 33' 40 to 45 Extensive sand bottom with scattered patches of flat
Pass rock.
CH-L 82' 17' 26* 20' 40 Small area of flat rock and gravel with significant
invertebrate growth; low relief.
Table 5b. Subaqueous bottom description for fishing grounds (from Moe, 1963).
Area Local Name est North (feet) Bottom Composition and Topography
SLongitude Latitude
CH-M Off Sanibel 82 00' 26' 25' 10 to 25 Sand bottom with a gentle slope to deeper water few
Beach to sparse areas of shell.
82 10'
CH-N Naples Grounds 81 40' 250 50' 5 to 30 Sand and mud bottom; sand occurs offshore and mud
to to occurs inshore by the mangroves. Very few areas of
816 55' 26 10' exposed rock.
a predominantly fine, mature quartz sand that UNE
comprise the inshore reaches and beaches. "1
Doyle collected and analyzed 114 offshore sand
samples, and lists locations (longitude and MA, tN
latitude), mean grain sizes, standard deviations, ROKS
percent fines, and percent calcium carbonate,
for each sample. Surface sediments were found 2
to reflect older drainage patterns. Specifically, UNE
nearshore quartz sand extends further offshore I \ ..-.
off Tampa Bay and Charlotte Harbor, than in ran BAY
other areas of the west Florida shelf. K_
Locker and Hine (1995) provide an -o
overview of the West-Central Florida Coastal 5
Studies Project. The project extends from 0o
Anclote Key south to Venice along the inner
shelf (up to 25 miles offshore). Initial 6M
reconnaissance included acquisition of more uNE
than 1,390 miles of side-scan sonar and seismic
data, in the effort to gain insight into long term
sediment transport pathways Figure 27. Neurauter's (1979) U-2 imagery
of bedform lineations.
Greg Brooks at Eckerd College is
involved in directing sedimentologic and bed studies of Florida's west coast inner shelf.
Surface grab samples (498) and vibracores (120) have to some extent been analyzed.
Preliminary findings have been presented by Berman and Brooks (1997), Brooks and others
(1997), Obrochata (1997), and Obrochta and others (1997). Brooks and others (in
manuscript) present results of the comprehensive study of surface sediments off the lower Gulf
Coast of Florida. The study extended some 90 miles from Anclote Key (Pinellas County) to the
north to south of Venice Inlet (Sarasota County) to the south, and offshore approximately 19
miles. Some 500 surface grab sediment samples were collected during three cruises in 1994
and 1995. An example of results (for phi mean grain size) is given by Figure 29a. Similar
output is given for per cent
carbonate, per cent organic,
carbonate mineralogy, and carbonate
constituents. Settling tube
granulometric results are also listed
for each sample. Brooks and
others (in preparation) report
similarly on the analysis of some
140 cores (Figure 29b) taken from
the same area described above.
Following are detailed county
accounts (from north to south) for
Florida's Lower Gulf Coast.
Figure 28a. Lower Gulf Coast offshore surface
sediment mean grain size (after Doyle, 1983).
Figure 28b. Lower Gulf Coast offshore surface
sediment percent carbonate (after Doyle, 1983).
Mean Phi Values
O4 t~
2. 17
t. 2j. 2A. 0.7. (.
1 i 1. 2 2
to t IAis t
2.7- 1.1-
*A a
1r .
"* '
Kb ,* U"
0 10 20
to. Lo. ^
I" Zia "* ^ y '
is 0. ti. to. q *' ,
im. tI o. aa
IA- W' 2 do.J- ^ S-" .e ^ ^ r
0'5 2 a-s.
< 1. 2.7t. 2yfla 'sA
Ga* to. &*3 "f 'aS
a'. t~ -o. to 1a \
2 7 s P
1A "* "6 ^^ u.i3r
GA D- d
GAP. toV ?.de
LORIDA t.o.' ai to
t4- 1A. a
LORIDA &8 IA A Venice
^\ ~ ~ ~ ar its t\ i*i "_y
a0s. i\ is. 2.7 1&:bs:: 0- .
GULF O0F \. -i Y
'-*"- -- \ gjto t1.7 l.Tlt
MEXICO Zr. I APrt
2to is.-&
l-2A 3A .-
^b vrOhl i
GULF F I u
Figure 29a. Example of plotted output (Phi Grain Size) and surface sample locations for
the study of Brooks and others (in manuscript).
0 10 20
* USGS Series Cores
* COE Series Cores
A SAR Series Cores
* WF Series Cores
* IRB Series Cores
Open symbol denotes core
attempt with no recovery
Figure 29b. Vibracore locations for the study of Brooks and others (in preparation).
46 4
26 1
General Description
Pinellas County, which has 34.7 miles of Gulf-fronting shoreline, extends from Tampa
Bay Entrance north to the Anclote River (Figure 30). Not included in this 34.7-mile reach is
a 4.8-mile segment between Anclote Keys to the north and Honeymoon Island to the south
where the mainland fronts on St. Joseph Sound. St. Joseph Sound is separated from the Gulf
by shoals (e.g.,
em erging Three -------------
Rooker Bar) "P ..
between Anclote An Key "--- ---i----- i
The remainder of I llll
ocean-fronting 1 "
stretches of Pinellas .. ....
C o u nty co insists of o-- -- ... . ... .
numerous coastal I-
b a r r ie r s o r k e y s a w . r .H.. ... |
c Hurric n- P Blind Ps---- 1
teristically are low -- .i ,, o
and narrow, range l c'..o.. 1 C haitl S 11 --l- Pt e r ----a ...
in width from 200 to Duni
2,000 feet with ct".....a .. a-.iii / Pan-:.-G.eo.. cM.-c- a
elevations of from Ps
+5 to +10 feet MLW C. *rw Pas......
(Young, Inc., 1987). R40 4-4hCan-y R-1
Origins of R-1K S 1 2O3 o 5 -, -1
Lower Gulf Coast L i-, 'M Ciii
barrier islands have Figure 30. Pinellas County coastal map showing locations
been described as of every tenth DNR reference monument.
landward migrating
features of an unknown mode of formation (Riggs and O'Conner, 1974) and, more recently, to
have an upward-shoaling mode of formation (Brame, 1976; Rosen, 1976; Kuhn, 1983; Davis
and Kuhn, 1982, 1985) controlled by the underlying rock topography (Hine and others, 1986).
The Holocene sedimentary sequence of these barriers and nearshore environs are represented
by 4 basic units: lagoon, shoreface, aeolian, and flood tidal delta/overwash sediments. The
majority of the sand-sized fraction of surface sediments (which constitutes 85 to 95 percent of
the sediments), is a mature, fine to very fine quartz sand with minor heavy mineral content; the
remainder of the sand fraction is carbonate skeletal material. Much of the silt/clay fraction is
organic material. The gravel fraction consists entirely of mollusc shells (Evans, 1983; Evans
and others, 1985; Hine and others, 1987).
The northern portion of Pinellas County (from about Honeymoon Island north) is
described by Tanner (1960) as a low wave energy shore (i.e., average annual breaker heights
are less the 0.33 feet), with the remainder of the county a moderate wave energy shore (i.e.,
annual average breaker heights range from 0.33 to 1.64 feet). The mean range of tide ranges
from 2.03 feet at the northern end of the county to 1.51 feet near Mullet Key (Balsillie and
others, 1987; Balsillie, 1987). Net longshore sediment transport is small at 50,000 cubic yards
to the south (U. S. Army, 1984), although local topography and bathymetry cause significant
reversals (Bruun, 1962; Rosen, 1976; Evans and others, 1985).
In terms of coastal morphology, Pinellas County has a diverse physiography. There
are ten coastal morphological segments in Pinellas County, including one mainland coastal
reach separated from the Gulf of Mexico by shoals, and one group of small, low islands, with
the remaining eight segments being barrier islands (Balsillie and Clark, 1992). Davis (1985)
also discusses Pinellas County's coastal morphology from Anclote Key to Egmont Key. These
reaches are, in addition to being affected by open ocean forces, subject to hydraulic influences
of 13 inlets (see Davis and Bland, 1986), and one Gulf-fronting sound. From north to south
these coastal barriers are described as follows.
Only about 3,000 feet of the southern portion of the largest island of the Anclote Keys
lies in Pinellas County. These low-lying islands comprise the Anclote National Wildlife Refuge
and Anclote Key State Preserve. Most of the four-mile length of Anclote Key is undergoing
non-critical erosion. While the key may be experiencing a high or significant erosion rate, it is
not a developed coastal barrier giving it non-critical status. Geology of the key has been
discussed by Kuhn (1983), Davis and Kuhn (1982, 1985), Davis and others (1985a).
Three Rooker Bar, between Anclote Keys and Honeymoon Island, are emergent
features first recognized in 1969 (Otvos, 1981). Geology and sedimentology of the bar has
been described by Gregory (1984) and Gibbs and Davis (1991).
About 4.8 miles south of the Anclote Keys lies Honeymoon Island, a low, flat island with
about 2.6 miles of Gulf-fronting shoreline. The island is wholly under the jurisdiction of
Honeymoon Island State Recreation Area, and is connected to the mainland by a causeway
constructed in 1966. Because of recreational interests, the southern one-half of Honeymoon
Island has been identified as a critical erosion reach. During the late 1960's, in preparation for
development, the southern portion of the island was filled and leveled, and three groins were
constructed. In 1969 about 450,000 cubic yards of sand, silt, and rock were dredged from just
offshore and placed along 6,000 feet of the southern Gulf shoreline of Honeymoon Island. The
fill remained relatively stable because of the substantial amount of rock fill (Clark, 1981). In
1989, 230,000 cubic yards of sand were placed along approximately 2,700 feet of the island's
southern shore (Davis and others, 1990), but was soon eroded. Beach fill projects for Pinellas
County are listed in Table 6.
Caladesi Island lies immediately south of Honeymoon Island. The two islands are
separated by Hurricane Pass, Willy's Cut and North Willy's Cut. Caladesi Island is accessible
only by boat. It is a low, flat coastal barrier with about 2.1 miles of Gulf-fronting shoreline, is
owned by the state, and is operated as Caladesi Island State Park. Caladesi Island beaches
remain natural, with no nourishment having been conducted or shore hardening structures
having been constructed. Clark (1993) notes that the northern part of the island is undergoing
significant erosion which is classified as non-critical because none of the recreational resources
are currently threatened. Geology of the island has been described by Brame (1976) and Davis
and others (1985b).
South of Caladesi Island, and separated by Dunedin Pass (currently closed), lies
Clearwater Beach Island. With about 3.1 miles of Gulf-fronting shoreline, the island averages
about 1,200 feet in width with natural elevations lying below +10 feet MLW. A causeway and
Table 6. Pinellas County beach nourishment and sources of borrow
material (after Balsillie and others, 1990).
Year Project Vo Fill Location Sand Source
(yd 3)
Honeymoon Island
1969 Nourishment 450,000 Honeymoon Island Offshore
1989 Nourishment 230,000 Honeymoon Island Trucked from inland site
Clearwater Beach Island
Clearwater Beach Island -
1949 Nourishment (4) 150,000 Clearwater Pass ?
southern end
1982 Nourishment (4) 180000 Clearwater Beach Island -just Clearwater Pass
north of Clearwater Pass
Sand Key
1961 Nourishment (4) 30,000 Madeira Beach Johns Pass ?
1969 Emergency Fill (1, 4) 143,000 Indian Rocks Beach Clearwater Pass
1972 Emergency Fill (3) 66,000 Sand Key Johns Pass ?
1973 Emergency Fill (1, 4) 400,000 Indian Rocks Beach Clearwater Pass
1977 Sand Transfer (4) 186,000 Just south of Clearwater Pass Clearwater Pass
1981- Sand Transfer (2) 600,000 City of Clearwater along north Clearwater Pass
84 __ ___ portion of Sand Key
Treasure Island stockpile
1986 Nourishment (3) 30,000 Redington Shores Treasure Island stockpile
from Johns Pass
1988 Nourishment (5) 529,150 Redington Sores and North John's Pass
.....Redington Beach
S Nourishment 19,000 Clearwater Trucked from inland site
1991 Nourishment (6) 1,325,000 Indian Rocks Beach Egmont shoals
1992 Nourishment (6) 1,060,000 Indian Shores and North Egmont shoals?
*_ '_ _Redington Beach
Just west and south
1993 Nourishment (7) 92,000 mile of beach beginning 1 offshore of Clearwater
mile south of Clearwater Pass
Treasure Island
1964 Sand Transfer (4) 10,000 Treasure Island Blind Pass
1969 Emergency Fill, and 793,000 Treasure Island Offshore and Blind Pass
Backpassing (1, 4)
1971 Renourishment (4) 75,000 Treasure Island Offshore of Johns Pass
1972 Renourishment (4) 155,000 Treasure Island Offshore
1976 Renourishment (2, 405,000 Treasure Island Offshore
Renourishment and
1978 Inlet Sand Transfer 50,000 Treasure Island Blind Pass
1980 Nourishment (6) 119,000 O'Brien's Laaoon John's Pass
Inlet Sand Transfer
1982 (3t Sand Transfer 52,000 North end Treasure Island Johns Pass
Table 6. Pinellas County beach nourishment and sources of borrow
material (after Balsillie and others, 1990).
Year Project Volue Fill Location Sand Source
Renourishment and
1983 dissent and 200,000 Treasure Island Blind Pass
1985 inlet Sand Transfer 60,000 Treasure Island north end Treasure Island stockpile
1985 60,000 Treasure Island north end f J Pass
(3) from Johns Pass
1986 Emergency Fill (2, 3) 543,000 South end of Treasure Island Offshore of Pass-a-Grille
1991 Inlet Sand Transfer 56,000 Just south of Johns Pass Johns Pass
Long Key
1968 Sand Transfer (2) 30,000 St. Petersburg Beach Blind Pass
Nourishment and
1975 Inlet Sand Transfer 75,000 St. Petersburg Beach Offshore and Blind Pass
1980 Nourishment (4) 143,000 North end on beach and Blind Pass
1980 Nounshe100,000 in shallow water Blind Pass
Nourishment and
19886 Noumen t (2, 3) 110,000 Just south of Blind Pass Blind Pass
Nourishment and
1986 Nourshment and 83,000 Pass-a-Grille Beach Pass-a-Grille ebb shoal
Emergencyt Fill (6)
1991 Renourishment (6) 280,000 Long Key north end Blind Pass
Mullet Key
Nourishment and
1964 Inlet Sand Transfer 139,000 Mullet Key Egmont Channel
Nourishment and
1973 Inlet Sand Transfer 505,000 Mullet Key Egmont Channel
(3) 1
Nourishment and
19e77 lt aansdfr 750,000 Mullet Key Gulf shore Tampa Harbor
1977 et Sand Transfer 350,000 Mullet Key south shore Tampa Harbor
Data Sources: (1) Walton (1977); (2) Young (1987); (3) Hobbs (1988); (4) U. S. Army
( Q4At)- f lean and I in (1Q000) (A) I1 R Armrny (I 4 (Z) T rknev andt AsSnr InP IQc19
bridges connect the island with the mainland. The island is highly developed as a resort and
residential community. All of the developed coastal reaches of Clearwater Beach Island are
armored with bulkheads and a groin field (about 26 groins) fronting the bulkheads. Two
concrete pier groins were constructed, one in 1952 and the other in 1962 (U.S. Army, 1984).
Beaches are generally narrow (R-35 to R-41), with a wide beach occurring from R-41 to R-46,
and no beach from R-46 to R-50. Two beach nourishment efforts have been conducted just
north of Clearwater Pass, one in 1949 and another in 1982. Clark (1993) notes that the coastal
reach between R-36 and R-40 is currently experiencing critical erosion.
To the south of Clearwater Beach Island lies Sand Key, the longest barrier island in
Pinellas County. Sand Key, separated from Clearwater Beach Island by Clearwater Pass (or
Little Pass), is a narrow, low, arc-shaped island occupying about 14.2 miles of Gulf-fronting
shoreline. The island ranges in width from 200 to about 2,000 feet, with elevations generally
less than +10 feet MLW. Numerous bridges connect the key with the mainland, with a bridge
also connecting the key with Clearwater Beach Island to the north. Sand Key contains 9
municipalities; most development is residential and resort oriented. Except for the northern
2,000 feet of Sand Key, the coastal barrier is highly developed with single- and multi-family
dwellings, and commercial structures. An offshore detached breakwater was constructed in
1985 (Terry and Howard, 1986) in the Town of Redington Shores (between DNR reference
monuments R-100 and R-101). The majority of the island has bulkheads, although there are
intermittent lots without such structures, and a groin field at the southern end of the island from
R-114 to R-125 which includes 37 groins built in 1957 (U. S. Army, 1984). The beach is wide
at the northern end of the island (R-51 to R-55), then narrows to the south to a reach with no
beach from R-60 to R-63. From R-63 to R-83 the beaches are narrow, south of which they are
wider. Except for the northern and southern reaches of Sand Key, Clark (1993) notes that the
majority of the barrier island (R-60 to R-115) is currently experiencing critical erosion. Sand
Key has been subject to a considerable number of nourishment and bypassing projects which
have been listed in Table 6.
To the south lies Treasure Island, separated from Sand Key by John's Pass. This low
and narrow 3.5-mile long coastal barrier island averages about 1,500 feet in width with peak
natural elevations generally less than +8 feet MLW. Bridges provide access to Treasure Island
from the mainland, from Sand Key and from Long Key to the south. Treasure Island is
developed as a residential and resort community. Treasure Island, also, highly developed with
single family, multi-family, and commercial development, is largely bulkheaded (intermittent lots
are not) although most bulkheads are now buried. A series of groins (57) were constructed in
1960 along the southern portion of the island (R-139 to R-143). Except for the northern 2,000
feet of the island where the beach is narrow, beaches range from wide to very wide attesting
to the success of the many beach nourishment projects to maintain beach dimensions. Initial
beach nourishment began in 1969 when a significant portion of borrow material was dredged
from a nearshore source, leaving a trench. Subsequent renourishment efforts also included
the construction of two groins in 1976 just north of Blind Pass to help retain the fill. In 1978,
the terminal groin at the north side of Blind Pass was increased in elevation to prevent sand
overtopping. Even so, the entire island is identified as an area of critical erosion because it is
a beach restoration project which requires maintenance (Clark, 1993).
Long Key is separated from Treasure Island by Blind Pass which has a history of
periodic closure. The key is about 4.1 miles in length with elevations lying between +5 to +10
feet MLW, and is highly developed for resort and residential use.. Bridges connect the key with
the mainland and Treasure Island. While there are shore-fronting lots without coastal
protection structures, there are many revetments and bulkheads along the entire northern
portion of Long Key from R-144 to R-154. Two kingpile groins were constructed just south of
Blind Pass in 1975 to help retain sand. A detached offshore breakwater exists at the north end
of Long Key and is aligned with the Blind Pass south jetty. South of R-156, Long Key is devoid
of coastal protection devices, and the majority of the key has wide beaches. Clark (1993)
describes all of Long Key to be a critical erosion area because it is a beach restoration project
which requires maintenance (see Table 6).
To the south of Long Key and Pass-a-Grille is the Bunces Key-Shell Key complex
(Crowe, 1984; Crowe and Davis, 1985). Landward of Bunces Key and Shell Key lie Cabbage
Key, Sawyer Key, Sister Key, and Summer Resort Key), characterized by elevations just above
mean high water and predominantly covered by mangroves. Accessible only by boat, there is
no development and no erosion control efforts have been conducted on these barrier islands.
Mullet Key, a v-shaped island, lies at the entrance of Tampa Bay (Egmont Channel).
Ranging in width from 1,000 to 2,000 feet, the key has 2.5-mile north-south trending reach
fronting on the Gulf, and 3-mile west-east trending segment extending into Tampa Bay. The
key is managed by the county as Ft. DeSoto Park with bridge access to the mainland. A
Federal beach erosion control project for the island was initiated in 1973, including a 60-foot
wide beach along a 6,750-foot reach with a 420-foot terminal groin, and a revetment 1,150 feet
in length. At the southern end of the Gulf-fronting portion of Mullet Key (R-180 to R-181) are
a terminal groin and revetment. The remainder of the Gulf-fronting beaches are natural and
for the most part are relatively narrow. Only a few thousand feet at the south end of Mullet Key
is undergoing critical erosion. Nourishment projects for the Key are listed in Table 6.
Inlet Sand Resources
Of all the counties fronting on the Gulf of Mexico, Pinellas County has historically been
subject to the greatest development pressure. This, in turn, has led to a greater number of
coastal studies. This more detailed knowledge is particularly apparent for inlets of the county.
Hurricane Pass: While tidal channels exist at both ends of Anclote Key and Three Rooker Bar
in northern Pinellas County, Hurricane Pass was the original inlet separating Honeymoon
Island to the north and the truncated northern tip of Caladesi Island to the south. Brame (1976)
describes the geologic history of Caladesi Island including the formation of Hurricane Pass
during a hurricane on October 25, 1921. The pass, which connects the Gulf of Mexico with St.
Joseph Sound, divided a coastal barrier formerly known as Hog Island.
A hurricane in September, 1950 caused substantial shoaling in Hurricane Pass,
although it continued to widen during the 1950's. In fact, since its opening in 1921, the inlet
gradually increased in size and flow until the early 1960's when the Honeymoon Island (or
Dunedin) Causeway was constructed. Construction of the Honeymoon Island Causeway,
completed in 1962, induced substantial shoaling thereby restricting water exchange between
St. Joseph Sound and the Gulf of Mexico. In recent years the inlet's cross-section has
gradually decreased while the controlling depth has increased (Lynch-Blosse, 1977; Lynch-
Blosse and Davis, 1977). From 1973 to 1976, the inlet axis migrated northward with accretion
occurring on the south side exceeding recession of the northern shore (Young, Inc., 1987).
The pass is dominated by the flood tidal cycle which has resulted in substantial interior
shoaling. Even so, and while the inlet throat has become progressively constricted, the inlet
appears to exhibit relative stability (Clark, 1981). The pass acts as a sink for sediment
transported off adjacent beaches which may account for the channel constriction. A 1.4-mile
segment of historically eroding beach to the north on Honeymoon Island experiences sand
transport southward into Hurricane Pass (Clark, 1993; Davis and others, 1990) and a 1.7-mile
segment of eroding beach to the south on Caladesi Island experiences sand transport to the
north (Lynch-Blosse, 1977; Lynch-Blosse and Davis, 1977; Clark, 1993). Hurricane Pass is
currently approximately 600 feet wide at its throat section and averages about seven feet deep.
Even though Hurricane Pass has never been dredged, the inlet has provided a corridor
for small craft navigation for nearly seventy years. In a sand source investigation for beach
restoration on Honeymoon Island, Davis and others (1990) assessed the ebb and flood tidal
delta sediments of Hurricane Pass. The flood tidal delta, protected from wave action except
for small waves generated within St. Joseph Sound and subjected to low tidal currents due to
the microtidal conditions, is covered by a substantial sea grass community which renders it
ineligible for nourishment consideration. The flood tidal delta covers an area less than 0.39
square miles and contains approximately 400,000 cubic yards of sediment. Cores show a
clean sand thickness of about 3.3 feet overlying 1.5 feet of muddy sand (mud content ranges
from 7 to 12 percent by weight). The total volume of beach quality sand is less than 200,000
cubic yards, much of which is covered with seagrasses. (Davis and others, 1990)
The ebb tidal delta of Hurricane Pass appears to be the best source of sand for
nourishment on Honeymoon Island, because of its proximity and availability. Covering less
than 0.39 square miles, it contains over 500,000 cubic yards of clean sand overlying 5.0 to 6.5
feet of muddy sand (mud content of less than ten percent by weight). The total volume of
beach quality sand is between 200,000 and 300,000 cubic yards. (Davis and others, 1990)
Other useful studies of Hurricane Pass include an inlet management plan (Jones, 1993),
ebb- and flood-tidal delta stratigraphies (Cuffe, 1991), ebb-tidal delta sand source description
(Gibeaut and Inglin, 1992), and detailed inlet improvements (U. S. Army, 1980a).
Willy's Cut: The north end of Caladesi Island experienced a major inlet breakthrough as the
result of impact of Hurricane Elena from August 31 September 1, 1985 (Clark, 1986). The
new inlet's location was located about 3,000 feet south of the island's north tip at Hurricane
Pass and is immediately north of a cuspate foreland called Lone Oak Point. Formation of the
new inlet is the replication of an earlier event in October, 1921 when Hurricane Pass was
created, separating Honeymoon and Caladesi Islands (formerly North Hog Island and South
Hog Island). Observations during its first three months of existence led investigators (Davis
and others, 1989) to describe the inlet as a broad washover fan with no significant tidal
channel. Increased sedimentation probably occurred during storm wave conditions produced
by Tropical Storm Juan in October, 1985. Wave energy and tidal currents during the winter of
1985-86 eroded a protective peat deposit leading to the development of a distinct channel
(Davis and others, 1989). The inlet channel deepened to over six feet, with a width of about
400 feet.
In the fall of 1986, a second inlet formed about 400 feet north of Willy's Cut. The short
subaerial reach between inlets is stabilized because of erosion resistant peat deposits. North
Willy's Cut formed as the sand shoreline north of the peat deposits receded and the barrier
spit became narrow and was overtopped. Due to the northward longshore transport direction
this inlet formed in an area with a sediment budget deficit.
It was speculated that were it not for the erosion resistant peat deposits between them,
both inlets should merge. Davis and others (1989) determined, using tidal prism calculations
from 1987 current measurements and cross-sectional area data, that both inlets flow areas are
in disequilibrium. North Willy's Cut had a flow area and tidal prism of about two-thirds that of
Willy's Cut.
Ross and Dorzback (1987) investigated the stability of these cuts and their potential
impact on the other inlets in the area. A mathematical model of Clearwater Harbor and St.
Joseph Sound was used to simulate and evaluate changes. The study showed the cuts to be
marginally stable and expected to increase in flow area. Such an increase was determined not
to significantly affect either Clearwater Pass or Dunedin Pass (if open), but would significantly
reduce flow through Hurricane Pass and the Dunedin Causeway bridge openings. Hurricane
Pass is expected to remain stable and new shoaling patterns will appear north of the Dunedin
Causeway. As the cuts trap littoral sediment, northern Caladesi Island is expected to
experience continued erosion stress.
The first-formed, southern inlet has closed. The northern inlet remains open, and while
relatively shallow, has merged with Hurricane Pass affecting hydraulic characteristics of
Hurricane Pass. The inlet was named Willy's Cut after the resident State park manager,
William Cutts.
Dunedin Pass: Dunedin Pass closed in late 1988 to early 1989. It originally connected the
Gulf of Mexico to St. Joseph Sound, separating Caladesi Island to the north from Clearwater
Beach Island to the south. In 1883, the flow through Dunedin Pass (then named Big Pass) was
the predominant influence on Clearwater Bay/St. Joseph Sound. Between 1883 and 1920,
considerable shoaling occurred, decreasing the width of the inlet. During this same time,
Clearwater Pass to the south increased in width, diverting flow from Dunedin Pass. When
Hurricane Pass was formed to the north in 1921, increased amounts of tidal flow were diverted
from Dunedin Pass, causing shoaling of the channel, southwestward realignment of the throat
and northward migration of the bar and channel.
Following construction of the Clearwater causeway in 1925-26, Dunedin Pass was
isolated from hydraulic influences of Clearwater Pass. Between 1926 and 1948, Hurricane
Pass carried most of the St. Joseph Sound tidal prism, which resulted in exacerbating the
migration of Dunedin Pass. In 1950, a hurricane caused considerable shoaling in Dunedin
Pass, reducing its width and depth, and influencing its northward migration. Progressively,
between 1950 and 1958, the pass returned to its original dimensions, forming an extensive
offshore bar from the shoal material deposited during the 1950 hurricane.
In 1958, the first phase of dredge and fill activity for Island Estates Development
(volume unknown) was initiated, causing reduction in the passes' channel width and tidal prism.
As development continued, Dunedin Pass channel progressively narrowed due to decreased
lagoon area, and the rate of inlet migration increased.
Between 1958 and 1972, inlet dimension changes were largely influenced by hurricanes
and tropical storms. Construction of the Honeymoon Island Causeway during 1960-63
compartmentalized St. Joseph Sound, and the tidal prism for Dunedin Pass decreased. The
impact of bay surface area reduction may be noted by the following relationship which
describes the process of aquatic mass transport through a tidal inlet:
Ab dh
v dt
where A, is the inlet cross-sectional flow area, Ab is the surface area of the connecting bay,
dh/dt is the rise or fall of the tide, that is, the time rate of change in the water surface elevation,
and v is the inlet channel current velocity.
With the construction of the causeways, Ab was reduced which, therefore, caused a
corresponding reduction in A, as noted in equation (1). The inlet channel current velocity, v,
was also reduced allowing increased sedimentation to occur. (Clark, 1981).
Inlet flow area reduction may be compared to inlet stability (the tendency towards
closure) by the relationship developed by Mehta and Hou (1974), according to:
2 y AC W
where C is the coefficient of stability, E, is the alongshore wave power per unit length of beach,
T is the tidal period, y is the unit weight of water, A, is the inlet cross sectional flow area, and
W is the work done by friction per pound of water over one-half tidal cycle. Over time, Dunedin
Pass experienced dramatic decreases in A, and W, and its stability coefficient C increased.
Large values of C denote a highly unstable condition subject to closure. Subsequently,
Dunedin Pass closed (late 1988 and early 1989) and a large region of St. Joseph Sound is no
longer served through direct exchange or renewal of water with the Gulf of Mexico.
In February, 1991, the closed inlet was breached and was still open in April, 1991. The
flow is minimal because the low tide width and depth is only 25 feet by about one foot at the
throat which is near the entrance bar across the inlet's mouth. The high tide width and
maximum depth is about 400 feet by three feet at the throat. The opening may close during
the summer months if sufficient sedimentation occurs during southwest wave activity. The
current opening still maintains a northwest offset.
The inlet has never been dredged. However, a proposal has been made by Pinellas
County to reopen the inlet to increase circulation of bay waters, to provide Gulf access for small
craft, and to reduce Clearwater Pass bridge openings. Opening the inlet by cutting a channel
across Mandalay Point has met with substantial opposition by those interests concerned with
protecting a least term nesting area, preserving an undisturbed natural beach/dune area,
preventing the erosion caused by the inlet on Caladesi Island, and disrupting a sea grass
community along the interior channel. The controversial issues regarding reopening Dunedin
Pass remain unresolved. (Division of Beaches and Coastal Systems, coastal construction
permit files DBS 87-196 and DBS 90-269).
Clearwater Pass: Clearwater Pass, located between Clearwater Beach Island to the north and
Sand Key to the south, is a natural inlet which connects the Gulf of Mexico with Clearwater
Harbor. The inlet was previously referred to as Little Pass and is shown as a narrow pass
(approximately 350 feet wide) on the 1879 United States Coast and Geodetic Survey chart
number 177. The inlet grew considerably over the next forty-five years and is shown to be
approximately 4500 feet (0.85 miles) wide on the 1924 United States Coast and Geodetic
Garden Memorial Causeway was constructed between Clearwater and Clearwater
Beach Island in 1925-1927 and provided a major restriction to flow between St. Joseph Sound
and Clearwater Harbor. Reduced bay area providing the tidal prism for Clearwater Pass had
a significant impact on the inlet's flow geometry. The inlet began to narrow as the north end
of Sand Key accreted. The formation of Hurricane Pass in 1921 also served to reduce the
effective tidal prism conveyed through Clearwater Pass.
By 1950, the inlet had narrowed to about 2500 feet. Subsequent development and
dredging activities further reduced the effective tidal prism through Clearwater Pass. In 1950,
the first phase of dredge and fill activity for the Island Estates Development was initiated. The
creation of new waterfront uplands from lagoonal dredging reduced the bay's potential tidal
prism. During 1961-1963, dredging for the Intracoastal Waterway and fill placement on spoil
islands added to bay area reduction, and the construction of Bascule bridge across Clearwater
Pass caused a reduction in flow velocities and an increase in frictional resistance. Although
not as impactive as the Garden Memorial Causeway on the Clearwater Harbor tidal prism, the
Honeymoon Island Causeway, constructed in 1964, created a further restriction to flow between
St. Joseph Sound and Clearwater Harbor. By August, 1974, the inlet's width had decreased
to only 750 feet. (DEP aerial photography).
Clearwater Pass was authorized as a Federal navigation project by an Act of Congress
on July 14, 1960. Subsequent work conducted includes an entrance channel 150 feet wide by
ten feet deep and two interior channels 100 feet wide by eight feet deep. Total length of the
navigation channels is about three miles. The Corps of Engineers has conducted maintenance
dredging activities in 1967, 1969, 1973, and 1977. The last maintenance project utilized the
dredge material for beach fill. During the three dredging projects in the 1960's, 320,822 cubic
yards of material were placed in subaqueous disposal sites. The two channel dredging projects
in the 1970's placed 311,629 cubic yards of material on the north end of Sand Key (U. S. Army,
In 1970, a study of Clearwater Pass and northern Sand Key was conducted by the
University of Florida, Coastal and Oceanographic Engineering Department, for the City of
Clearwater. Because the inlet's depth was increasing with the decrease in inlet width, the
bridge piles lost sufficient penetration to warrant safety concerns (University of Florida, 1970).
The City obtained an insurance policy on the bridge with Lloyds of London which required the
implementation of inlet stabilization design recommendations resulting from another University
of Florida study (i.e., a physical hydraulic scale model study of Clearwater Pass). The hydraulic
model study (Olsen, 1973) recommended the construction of two inlet jetties and excavation
within the pass to increase the flow area and to reduce current velocities. The City completed
construction of the 4200- foot long south jetty on Sand Key in 1975. The 550-foot long north
jetty was constructed at the south end of the public beach on Clearwater Beach Island in 1981.
Jetty construction and inlet dredging resulted in an increased inlet width of 1,380 feet. The City
of Clearwater Beach was authorized to dredge 1.13 million cubic yards of sand from the inlet
and place 250,000 cubic yards as fill around the threatened bridge piles. A subsequent
monitoring report was forthcoming from Wang and others (1977).
Following the purchase of a dredge in 1979, the City commenced inlet excavation in
February 1981 (Newman, 1983). Between 1981 and 1983, the City placed approximately
600,000 cubic yards of sand fill as beach nourishment along northern Sand Key although about
150,000 cubic yards of material was lost during the subtropical storm of June, 1982. During
late 1983 through early 1984, the City placed approximately 80,000 cubic yards of inlet sand
along the inlet's north shore beach and approximately 240,000 cubic yards of inlet sand along
Sand Key.
Newman (1983) evaluated various hydraulic relationships and determined the inlet to
be stable. Hine and others ( 1986) report an ebb tidal delta sediment volume of 7.02 x 106
cubic yards based upon a 1984 survey. The beaches immediately north and south of the inlet
are currently stable or accreting.
John's Pass: John's Pass, located between Sand Key and Treasure Island, is a small tidal
inlet connecting the Gulf of Mexico with Boca Ciega Bay. John's Pass appears to have been
opened by a hurricane in September, 1848 (Mehta and others, 1976a). The inlet has
maintained stability since opening and has not migrated along the coast as have Blind Pass
to the south and Indian Pass to the north.
In 1929, the U.S. Army, Corps of Engineers closed Indian Pass, a wild migrating inlet
located adjacent to the Narrows at Indian Rocks Beach to the north of John's Pass. The
closure of Indian Pass may have influenced the continued stability of John's Pass to which its
tidal prism was diverted. A bridge was constructed across John's Pass in 1926 and replaced
with the existing bridge in 1969.
In 1960, 94,000 cubic yards of material were dredged from John's Pass by local
interests. The material was spoiled on the outer bar of the pass located 20,000 feet offshore
and south of the dredged channel. (U. S. Army, 1969).
Erosion problems along the City of Madeira Beach to the north prompted the city to
construct a groin field of 37 timber pile and panel groins along the Gulf shore in 1957. A study
of the erosion on Madeira Beach by the University of Florida, Coastal Engineering Laboratory
recommended a north jetty for John's Pass (University of Florida, 1960). In 1961, the City
constructed a 460-foot curved jetty on the north side of the inlet and dredged 30,000 cubic
yards of sand which was placed on the beach to the north of the jetty (U. S. Army, 1966).
By the authorization of Section 107 of the 1960 River and Harbor Act, John's Pass
became a federal navigation project. The navigation channel's planned dimensions were 50
feet wide by 10 feet deep across the outer bar, 100 feet wide by 8 feet deep into the inlet, and
100 feet wide by 6 feet deep to the Intracoastal Waterway. In 1966, a total of 95,000 cubic
yards of material was removed for the navigation channel and placed in an offshore spoil area
south of the channel (U. S. Army, 1969). The Corps of Engineers also constructed a 920-foot
long revetment along the south shoreline of John's Pass (U. S. Army, 1966).
The University of Florida, Coastal Engineering Laboratory, conducted two studies during
the late 1960's at John's Pass. The first involved a surface current study to investigate the
effects of the offshore dredge spoil on the tidal currents at the inlet's entrance (University of
Florida, 1966). A second study investigated the possible effects of the proposed new bridge
on the hydraulics and shoreline erosion of John's Pass (University of Florida, 1969).
The offshore spoil area south of John's Pass emerged and migrated shoreward until it
attached to the north Treasure Island beach forming O'Brien's Lagoon (now extinct). In 1973-
74, Sedwick and Mehta (1974) studied the hydraulics of a small inlet connecting the Gulf of
Mexico with O'Brien's Lagoon. Sedwick (1974) modeled the hydraulics and determined
hydraulic constants for the inlet (MOB Inlet) using mehtodology suggested by O'Brien and
Clark (1973, 1974). Sedwick and others (1975) chronicled the history of O'Brien's Lagoon and
MOB Inlet. Approximately 75,000 cubic yards of material were removed from the bar
entrapping O'Brien's Lagoon in 1971 using land based equipment, and spoiled along a 1,600
foot stretch of beach one mile south of the inlet (U. S. Army, 1975).
Field studies were conducted at John's Pass by the University of Florida, Coastal and
Oceanographic Engineering Department in August, 1974. Spatial and temporal velocity profiles
were obtained at the inlet's throat section to measure bed shear stress as a function of the tide
stage (Mehta and others, 1975, 1976a; Mehta, 1978). Also in 1975, a fluvio-hyrdrographic
study was conducted by the University of Florida, Hydraulic Laboratory, to evaluate the impact
of a proposed marina in John's Pass (Christensen and Langley, 1975).
Mehta and others (1976b) discuss the changes in the inlet cross-sectional area of both
John's Pass and Blind Pass (to the south) between 1873 and 1974. The cross-sectional flow
area of John's Pass measured at the inlet throat increased from approximately 5,100 square
feet to 9,500 square feet during this 100 year time interval for an 86 percent increase. This
increase was accompanied by a dramatic decrease in the flow area at Blind Pass which also
provides water exchange between the Gulf of Mexico and Boca Ciega Bay. Of note, is the sum
total of both inlets' cross-sectional flow areas, though decreasing somewhat in 1926, has in
1957 and 1974 approximated the combined area in 1873. As less of the Boca Ciega Bay tidal
prism has flowed through Blind Pass, more of the tidal prism has flowed through John's Pass
causing an equivalent enlargement in the John's Pass flow area and reduction in the flow area
of Blind Pass (Mehta and others, 1976a).
Hine and others (1986) computed a total sediment volume in the ebb tidal shoals to be
approximately 5,020,000 cubic yards based on 1984 survey data. Between 1979 and 1985,
over 230,719 cubic yards of material were removed from the pass in several Corps of
Engineers maintenance dredging operations. The sand was placed as beach fill on Treasure
Island and to fill in O'Brien's Lagoon (Hine and others, 1986). In 1988, some 529,000 cubic
yards of sand was dredged from John's Pass and placed (backpassed) on Sand Key along the
Town of Redington Shores (Dean and Lin, 1990). Walther and Douglas (1993) assess the
anticipated recovery history of the borrow site based on historical longshore transport rates.
Blind Pass: Historically unstable and administratively controversial, Blind Pass, located
between Treasure Island to the north and Long Key (St. Petersburg Beach) to the south,
connects the Gulf of Mexico with Boca Ciega Bay. Except for a short (approximately 1200 feet)
length of the entrance channel, the inlet parallels the coast with a pronounced southerly
downdrift offset.
Blind Pass is shown on charts as early at 1777 (Mehta and others, 1976a). During the
past century, the inlet has not been of great importance to navigation interests and in recent
years the shallow depths have precluded all but small pleasure craft. Near the midpoint of
Treasure Island to the north of Blind Pass, a former small inlet shown on an 1883 government
survey was subsequently closed in 1916 by the Corps of Engineers. This inlet reopened
between 1916 and 1921, but a hurricane closed it in October, 1921. The inlet reopened again
in 1930 and closed permanently in 1935. In 1926, when the county constructed the Treasure
Island road and bridge across John's Pass, a bridge was also constructed over Blind Pass near
its north end.
Mehta and others (1976a) also discuss the changes in the surface area of north Boca
Ciega Bay from 1873 to 1974. Based upon a review of U.S. Coast and Geodetic Survey charts,
U.S. Department of Agriculture photography, and National Ocean Survey photography, dredge
and fill operations in Boca Ciega Bay between 1926 and 1969 caused a 26 percent decrease
in the bay surface area. This decreased bay surface area should be directly related to a
reduced tidal prism and flow regime at Blind Pass.
The earliest modification of Blind Pass took place in 1937 when a small jetty or terminal
groin was constructed on the inlet's south side. The Blind Pass channel had migrated south
about 7,000 feet, and a low jetty was constructed along the south shore of the channel to
prevent further southward migration. Erosion also prevailed along the south end of Treasure
Island and in 1960 the city installed a groin field of 56 groins (University of Florida, 1960). A
425-foot long terminal groin was constructed in 1962 on the north side of Blind Pass to further
stabilize the Treasure Island shoreline (U.S. Army, 1966).
Blind Pass has been dredged several times to obtain sand fill for Treasure Island beach
nourishment or to bypass sand southward to Long Key. The first dredging project in 1964
obtained 10,000 cubic yards to nourish the eroded south end of Treasure Island called Sunset
Beach (U. S. Army, 1966). As part of a major beach restoration project for Treasure Island in
1969, approximately 100,000 cubic yards of fine-grained sand was removed from Blind Pass
and placed along Treasure Island. Blind Pass is one of 3 authorized borrow areas for the
Treasure Island federal erosion control project.
To mitigate the continued severe erosion south of Blind Pass, the City of St. Petersburg
Beach excavated 75,000 cubic yards of sand from Blind Pass in 1975 and transferred the
material to a 1/2-mile of beach at the north end of Long Key. The City also constructed a south
jetty extension of 171 feet and restored the original 90 feet. Two groins were also constructed
in the fill area. The Corps of Engineers also nourished southern Treasure Island with nearly
405,000 cubic yards of sand and built two impermeable sheet pile groins north of Blind Pass.
With this nourishment material and a substantially reduced ebb tidal flow through the inlet, Blind
Pass was overwhelmed with littoral sediment and closed in April, 1978.
Blind Pass had been trying to close during the 1970's. Evidence of this instability was
discussed by Clark (1978). Based upon measurements obtained during a University of Florida
field study in 1974, the Blind Pass tidal prisms were calculated to range between 1.15 and 3.45
X 107 ft3 and the inlet throat cross-sectional area below mean low water was 442 ft2 (Diaz,
1975). Using the O'Brien (1969) relationship for inlets with jetties in sedimentary equilibrium,
given by:
Ac = 4.69x10-4 P.85 (3)
where A, is the equilibrium minimum flow area, and P, is the spring tidal prism. Assuming the
spring tidal prism to be Ps = 3.45 x 107 ft3, equation (3) yields an equilibrium flow area, A,, of
1200 ft2. The measured flow area of 442 ft2 was only 36.8 percent of the flow area required for
sedimentary equilibrium. It was therefore concluded that the inlet was unstable at the time of
the measurements (1974) and was trying to close. Aerial photography of 1974, 1976, 1977,
and 1978 reveal the closure process. (Clark, R.R., 1978, Blind Pass, Pinellas County: Beaches
and Coastal Systems Inlet file)
During the first two weeks of May, 1978 the Corps of Engineers supervised an
emergency project to excavate 4,000 to 4,500 cubic yards of sand/shell from Blind Pass by
dragline and to place the material on the upland of Treasure Island for the city's dune
restoration project. Dredging had reopened the inlet by May 13, but the inlet closed on May 14.
In November, 1978, the Corps of Engineers excavated about 50,000 cubic yards of sand and
reopened Blind Pass (U. S. Army, 1980b). The inlet remained open although the material was
placed on Treasure Island.
Using Blind Pass dredged material quantified from 15 cores obtained in 1978 (U. S.
Army, 1980b), the initial beach restoration for the Federal erosion control project on Long Key
was completed in March 1980 and consisted of the placement of 143,000 cubic yards of
material along the northern 2,800 feet of island beach and of the placement of 100,000 cubic
yards of material just offshore to act as a partial breakwater and a beach sediment source. All
the material was excavated from Blind Pass (U. S. Army, 1980b). In 1981, 11 core borings
were obtained from Blind Pass (U. S. Army, 1984). Sediments of the inlet deposit had a
composite mean grain size of 1.41(p with a composite standard deviation of 1.90(p. Silt content
ranged from two to nine per cent and a mean of four per cent. Shell content ranged from two
to 40% with an average value of 14%. In 1983, the north terminal groin was extended 130 feet
to act as a jetty and to reduce beach sediment entrapment. Another 200,000 cubic yards of
material was also dredged from the inlet in 1983 and placed along the south end of Treasure
Island (Sunset Beach). (Hine and others, 1986) In January and February, 1991, approximately
280,000 cubic yards of material was again removed from Blind Pass. The "after losses"
estimate of material remaining as beach fill on northern Long Key is about 200,000 cubic yards.
Coastal Planning and Engineering, Inc. (1992) has submitted an inlet management plan
to Pinellas County (Board of County Commissioners) which contains detailed information about
the inlet.
Pass-a-Grille: South of Long Key lies Pass-a-Grille, a tidal inlet with 2 entrance channels. The
2 channels fork near the end of Long Key and were separated by a tiny island (emerged shoal)
named Shell Key, prior to its merging with Bunces Key. Historically unconfined by a southern
barrier, Pass-a-Grille is now bounded on the south by North Bunces Key which emerged in the
1960's from the ebb tidal delta of the south channel. This new island has effectively blocked
tidal flow through the south channel. The large tidal prism is now carried through the north
The north channel has been stabilized from any migration trend by the construction of
a terminal groin at the south end of Long Key. Initially in 1941, the Town of Pass-a-Grille built
a 120-foot long king pile and panel groin at the end of First Street to stabilize the south beach
of Long Key. Between 1959 and 1960 the Corps of Engineers built a boulder mound groin at
the same location of the earlier groin built by the Town. This structure was extended for a total
length of 436 feet in 1962. Due to substantial deterioration since 1978, the terminal groin was
reconstructed by the Corps of Engineers in 1984. (Division of Beaches and Coastal Systems,
Coastal Construction Permit File number DBS 83-55).
A Federal navigation project was approved for the north channel of Pass-A-Grille in
1964. The authorization provided for a 10-foot deep by 150-foot wide entrance channel and
an 8-foot deep by 100-foot wide interior channel to connect the gulf with the Intracoastal
Waterway. In 1966, a one-time dredging project was conducted involving the removal of
162,000 cubic yards of sand with disposal offshore. (U. S. Army, 1967). The ebb tidal delta
of Pass-a-Grille has been a source of sediment for recent beach restoration and maintenance
nourishment projects to the north. Following the storm erosion inflicted by Hurricane Elena and
Tropical Storm Juan in 1985, the Corps of Engineers conducted emergency fill operations
obtaining 653,000 cubic yards of sand from the Pass-a-Grille shoals. In 1986, the Corps
placed 543,000 cubic yards of this material on Treasure Island and 110,000 cubic yards on the
southern reach of Long Key. In 1988, the Corps completed the beach restoration along
Redington Shores and North Redington Beach with the placement of 529,150 cubic yards of
sand obtained from the Pass-a-Grille shoals.
Three Unnamed Inlets: Although the exact date is uncertain, North Bunces Key breached
within a three month period from early November, 1981, to late January, 1982 (Crowe, 1984).
Since 1961, North Bunces Key was breached on two other occasions, both times with the
formation of unstable tidal inlets. The first inlet opened about 1966 and closed in mid-1970.
The second inlet opened in about 1972 and closed by late 1973. (Crowe, 1984). The last inlet
which divided North Bunces Key survived nearly ten years before closing.
Another unnamed inlet breached South Bunces Key during hurricane Elena in 1985
(Clark, 1986). South Bunces Key has attached to Mullet Key at its south end but the entrapped
lagoon connects with Bunces Pass at the north end. This inlet created during Elena is now
closed. Closure of the lagoon's north opening at Bunces Pass may ultimately occur, thus
entrapping a barrier lagoon.
Bunces Pass: Part of the Tampa Bay tidal delta complex, Bunces Pass lies north of Mullet Key
and south of Cabbage Key and North Bunces Key. North Bunces Key emerged in the 1960's
from the large ebb tidal delta complex between Bunces Pass and Pass-a-Grille.
Bunces Pass is a natural tidal inlet with a large ebb tidal delta and has been stable with
a small increase in size during the past 100 years. Davis and Gibeaut (1990) state "this
stability is made possible by the large tidal prism and the large sediment accumulations which
have recently emerged into small barrier islands on each side of the seaward inlet channel...
This tidal delta has increased in size during the past few decades probably in response to the
closure of the south channel of Pass-a-Grille".
Bunces Pass is about 1,300 feet wide at its throat between North Bunces Key and Mullet
Key. Depths average 18 feet and the inlet has never been dredged.
Egmont Channel, Southwest Channel, and Passage Key Inlet: The entrance to Tampa Bay
consists of three main channels connecting to the Gulf of Mexico. From north to south, these
channels are Egmont Channel, Southwest Channel, and Passage Key Inlet. Passage Key Inlet
between Anna Maria Island and Passage Key actually lies in Manatee County but is included
in the discussion here because of the close proximity of all three inlets. Southwest Channel
is a broad natural channel between Passage Key and Egmont Key, and Egmont Channel is the
main shipping channel located between Egmont Key and Mullet Key. These latter two Tampa
Bay entrance channels are actually located within Hillsborough County. They are, however,
discussed here because of the importance of their immense ebb tidal delta complex.
The tidal prisms and depths of these inlets decrease from north to south. Southwest
Channel, which is not maintained for navigation is about 7,200 feet wide between the islands
and has an average depth of about 21 feet. Depths in excess of 30 feet are found adjacent to
the south end of Egmont Key. Egmont Channel with about twice the flow area is about 8,300
feet wide between the islands and has an average depth of about 48 feet. The channel flow
width between the -6 foot MLW contours on either side of the channel is about 3,300 feet.
Maximum channel depths reach 90 feet adjacent to the north end of Egmont Key.
The entrances to Tampa Bay are ebb tide dominant and an insignificant flood tidal delta
exists. The immense ebb tidal delta exceeds 400 million cubic yards of sediment and
represents the largest tidal delta complex on the coast of Florida. Egmont Channel is a
federally authorized navigation channel with an authorized entrance channel width of 700 feet
and authorized depth of 46 feet. Hine and others (1986) reports about 13,500,000 cubic yards
of sediment being dredged from the entrance channel and being disposed mostly offshore
between 1951 and 1981. Three channel maintenance projects have involved the placement
of dredged material on Mullet Key beaches. A project in 1964 included the placement of
139,000 cubic yards and another project in 1973 included the placement of 505,000 cubic
yards. In a 1977 channel maintenance project, 350,000 cubic yards of material were placed
on the Mullet Key south beach fronting on Tampa Bay and 750,000 cubic yards were placed
on the Gulf beach.
The ebb tidal shoals offshore and north of Egmont Channel have been used recently
as the sand source for beach restoration on Sand Key. Approximately 1,320,000 cubic yards
of this shoal sediment has been removed north of the channel and placed along Indian Rocks
Beach in 1990 and another 1,100,000 cubic yards along Indian Shores in 1991. Given the
large volume of sediments in the Tampa Bay ebb tidal delta and the scarcity of surficial
sediments offshore from the Pinellas County coastal barriers, the Egmont shoals may continue
to play a prominent role as a sand source for beach nourishment.
Offshore Sand Resources
The barrier islands and surrounding nearshore areas are formed of a relatively thin sand
lens lying on top of Tertiary limestone (Evans, 1983; Evans and others, 1985; Hine and others,
1987). The barrier islands form the thickest portion of the lens, extending vertically no more
than 16 to 20 feet from the highest dunes to the underlying limestone rock surface below (Davis
and others, 1982; Evans and others 1985). Nearshore sand seaward of the islands thins and
pinches out within 1,600 to 5,000 feet of the beaches. Further seaward, and even within the
nearshore zone, lie numerous exposures of the St. Marks Formation (Cherry and others, 1970;
Riggs and O'Conner, 1974), which has subsequently been reassigned to the Tampa Member
of the Arcadia Formation (Scott, 1988). The Holocene sedimentary sequence of these barriers
and nearshore environs are represented by 4 basic units: lagoon, shoreface, aeolian, and flood
tidal delta/overwash sediments. The majority of the sand-sized fraction of surface sediments
(which constitutes 85 to 95 percent of the sediments), is a mature, fine to very fine quartz sand
with minor heavy mineral content; the remainder of the sand fraction is carbonate skeletal
material. Much of the silt/clay fraction is organic material. The gravel fraction consists entirely
of mollusc shells (Evans, 1983; Evans and others, 1985; Hine and others, 1987).
Winston and others (1968) report that there is no sediment being supplied to the
Pinellas County coast by rivers. They collected and analyzed some 440 sand samples off the
northern barrier islands of Pinellas County, extending from Anclote Key south to the middle part
of northern Long Key. Descriptions for offshore transects were made for Clearwater Beach
Island, north Sand Key, south Sand Key, and Treasure Island. Descriptions follow:
Clearwater Beach Island: Sedimentary units from onshore to offshore are: 1. recent beach
and inlet sand and shell, 2. muddy sand, 3. recent offshore bar sand and shell, and 4.
Miocene limestone. Thicknesses of unconsolidated sediments range from 18 feet at the
shoreline to a "feather edge" one mile offshore.
Northern Sand Key: The offshore sequence is the same as for Clearwater Beach Island,
except that the muddy sand zone is much narrower and the recent offshore bar sands and
Miocene limestone lie much closer to shore. The Miocene limestone is exposed over much of
the nearshore area at water depths of 16 to 20 feet, and covered with local, patchy
accumulations of bar sands, the elongate bar sands cover, in some cases, considerable areas
but are generally less than 6 feet thick.
Southern Sand Key: It might be interpreted that the offshore sequence proceeds as: 1. beach
and inlet sand and shell, 2. recent offshore bar sand, 3. recent mud and sand, and 4.
Miocene limestone. North of the traverse, limestone lies exposed at water depths of 12 to 20
feet. Nearer John's Pass, bedrock exposure occurs in considerably deeper water and overlying
sediments are considerably thicker.
Treasure Island: Offshore sediment distribution is similar to southern Sand Key, except for a
large exposure of offshore bar sand nearshore just north of Blind Pass, and a deposit of shelly
sand off the south end of the island. Shelly sand "underlies" the entire area at a uniform depth
of about 20 feet, and may exceed 20 feet in thickness. Offshore bar sand and shell, and bar
sand which overlie the shelly sand might attain a thickness of 16 feet.
The authors mapped results 2.5 to 3.5 miles offshore of Pinellas County's coastal barrier
islands. Included are detailed (1" = 1 mile) geologic maps of offshore subaqueous surface
sediments and outcrops, and isopach maps of sediments (Figures 31a through 31d, and 32a
through 32d).
In 1969, 792,866 cubic yards of sand were placed on Treasure Island (U. S. Army, 1968;
University of Florida, 1971). A substantial amount of this material was taken from the
nearshore (the remainder was backpassed from Blind Pass). This was one of but only several
projects which, up until that time, derived its borrow source from nearshore sediments. Three
shore-parallel trenches, 20 feet in depth and totalling 6,213 feet in length, were dredged 1,500
to 2,000 feet offshore. Some sedimentological information is provided by the U. S. Army
(1968) including a stratigraphic section based on 19 cores (17 from the nearshore borrow area
and two from Blind Pass).
The U. S. Army (1971) reports on design information for subsequently restored Gulf-
fronting beaches of Mullet Key. The selected borrow area was located in seven to nine feet of
water, and "sized" to meet needs of the restoration project. Borrow area excavation was
designed to be limited to sediment lying above -20 feet (MLW?) to "... avoid possible
detrimental effects to beach stability." Thirty-one cores were taken from 1,000 to 4,400 feet
offshore from which stratigraphic sections were compiled (Figures 33a and 33b). The
document also provides additional information including core logs, selected granulometric
parameters for each 5-foot length of core, and granulometric plots.
U. S. Army (1975) discusses the third nourishment of the Treasure Island project, whose
fill material was to be derived from the same borrow area that was used for the 1969
restoration. Excavation was designed to be taken adjacent to the south end of the previously
used nearshore borrow trench, not to exceed -25 feet MLW. This document contains
geotechnical information including borrow area sites for the original 1969 project nearshoree
trench and Blind Pass), 1972 renourishment (John's Pass site), and third nourishment, boring
logs, stratigraphic sections, etc.
Some additional geotechnical information is presented by the U. S. Army (1978) for
areas inside of (11 cores) and outside of (three cores) Blind Pass. Core boring logs are
North of Tampa Bay, Neuratuer (1979) reports a decrease in abundance of bedforms
and an increase in rock outcrops. Off of Anclote Key (Tarpon Springs) are two major fields of
giant- to large-scale bedforms in water depths of from 33 to 60 feet. Average relief is two feet.
Figure 31a. Surface sediment isopach map of offshore area from Anclote Key south to the vicinity
of Dunedin Pass, Pinellas County, FL (from Winston and others, 1968; see Figure 31c for
explanatary notes, Figure 310b for scale).
Figure 31 b. Surface sediment isopach map of offshore area from Dunedin Pass south to Indian
Rocks Beach, Pinellas County, FL (from Winston and others, 1968; see Figure 31 c for explanatary
Figure 31c. Surface sediment isopach map of offshore area from Indian Rocks Beach south to south-
central Sand Key, Pinellas County, FL (from Winston and others, 1968; see Figure 31d for scale).
Figure 31d. Surface sediment isopach map of offshore area from south-central Sand Key south to
St. Petersburg Beach, Pinellas County, FL (from Winston and others, 1968; see Figure 31c for
Figure 32a. Subaqueous surfacial geologic map of offshore area from Anclote Key south to the
vicinity of Dunedin Pass, Pinellas County, FL (from Winston and others, 1968; see Figure 32c for
symbols, Figure 32b for scale).
Figure 32b. Subaqueous surfacial geologic map of offshore area from Dunedin Pass south to Indian
Rocks Beach, Pinellas County, FL (from Winston and others, 1968; see Figure 32c for symbols).
Figure 32c. Subaqueous surfacial geologic map of offshore area from Indian Rocks Beach south to
south-central Sand Key, Pinellas County, FL (from Winston and others, 1968; see Figure 32d for
Figure 32d. Subaqueous surfacial geologic map of offshore area from south-central Sand Key south
to St. Petersburg Beach, Pinellas County, FL (from Winston and others, 1968; see Figure 32c for