{'fraction_non_alphanumeric': 0.026172806785051683, 'fraction_numerical': 0.01258945136496157, 'mean_word_length': 4.805, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Bed Load Distribution Analysis of Pondo Poboya River to The Hydraulics Flow Parameters

The aim is to know the effect of bedload sediment to river hydraulics parameters. The research was conducted by taking samples in three-part of the river. Each location is taken ten cross-sections with left, middle, and right parts of the river. Bedload sediment is calculated by the grain analysis method. There are several approaches in determining the roughness: Manning, Raudkivi, Subramanya, Meyer, and Muller roughness. From the analysis results, sediment in the form of fine sediment (d ≤ 0.15 mm) located in the middle of the cross-section does not settle due to high velocity. In contrast, in the wet area, the velocity is smaller so that grain material is deposited. The relationship of bedload sediment to the morphological form of the river shows that the middle part has the most material content in grain sediment (d ≤ 0.15 mm). The wet edge has the most content in gravel and sand (d < 6 mm). The Manning equation obtained a minimum roughness of 0.0257 and a maximum coefficient of 0.0365 with an average value of 0.0311. This value is matched with the coefficient of roughness on the Manning table does not differ much, i.e., natural, straight, and meandering channels.


Introduction
The mechanism of sediment bed transport that occurs in open channels in natural rivers is very complicated and complex. There are many parameters related to sediment flow and transport. Information on the characteristics of bed sediment material flow is needed in planning and operations regarding hydraulic structures. The direct sampling method is more reliable than the calculation method in predicting sediment discharge in a river or open channel. Many obstacles were encountered during field measurements, and sediment sampling often could not be carried out following the required sampling standards. This will have an impact on the prediction results obtained. The estimation of river flow may require the attention of engineers. The water endurance is specified in the water depth and velocity estimation, which is conventionally depicted by the equation. In this equation, the channel and the flow characteristics that induce resist the force or lose energy to the flow [1]. The review shows that many factors influence the flow in a meandering river: the shape of the cross-section, flow depth, sinuosity, Reynolds no, roughness ratio, side slope, etc. [2]. Early studies focused on deepwater zones with relatively small roughnesses, such as plain rivers. The Manning formula is an empirical relation that accounts for the flow velocity, hydraulic radius, and channel slope in plain rivers [3]. The friction factor values in gravel-bed rivers depend on the particle size of the bed material, bedforms, channel geometry, longitudinal slope, and non-dimensionalized flow depth (flow depth/sediment size) as a IOP Conf. Series: Earth and Environmental Science 930 (2021) 012024 IOP Publishing doi: 10.1088/1755-1315/930/1/012024 2 hydraulic condition. Among these parameters, grain size and bedforms have the greatest impact on the friction factor and sediment transport in most gravel-bed rivers with the deep flow [4]. The flow resistance consists of two parts: 1) grain resistance or skin friction which depends on the bed grain size, and 2) form resistance which depends on the bedform geometry and flows depth. Flow resistance is a fundamental control of flow hydraulics in streams and rivers. It is not only determining the amount of water a channel can convey through its influence on velocity (and thus flow depth) but also controlling the distribution of shear stress around the channel boundary and the magnitude and distribution of bed and bank erosion. Therefore, a thorough understanding of flow resistance is necessary to improve natural hazard prevention and mitigation [5]. Flow resistance in rivers and open channels are of enormous importance in river engineering. Furthermore, its dynamics vary from compartment to compartment depending upon the bottom roughness and the variability of lateral flow depths. Accurate estimation of river flow resistance is important to predict the stage-discharge relationship in rivers, thus evaluating the likelihood of river flooding and issuing warnings of flooding. The issue of deciding the flow velocity and depth in a channel for a known discharge, remains a frequently revised topic in fluvial engineering. One of the important causes is the trouble in deciding precisely friction factors in a river channel [6].
The degree of roughness depends on several factors. The most important in open-channel flow are surface roughness of the bed material, cross-section geometry, channel variations, obstruction to flow, type and density of vegetation, and degree of channel meandering. In general, all factors that tend to cause turbulence and retardance of flow, hence energy losses, increase the roughness coefficient. Those that cause smoother flow conditions tend to decrease the roughness coefficient [7]. Similar research has examined the grain character of the sediment to evaluate a channel roughness formula to obtain a channel roughness formula that was appropriate for its use and application [8][9][10][11]. The relationship between the characteristics of the riverbed material and its geometry shows that the middle part of the river has the highest content of coarse-grained soil (d0.150 mm). In contrast, at the edge of the river it has the highest content of fine-grained soil (d0.150 mm). Meanwhile, [9] researched the distribution pattern of surface sediments based on water depths to determine the condition of the Dompak island waters, namely the reclamation of the mangrove area and being developed into an international ferry port area. For [10], he carried out direct measurements on the Opak River, which originates at Mount Merapi. Analysis of the measurement data to obtain the frictional velocity u* and the numerical integration constant Br using the Clauser method. The flow velocity distribution pattern in natural rivers does not always have a maximum value in the middle section. The flow velocity distribution increases as it approaches the surface and vice versa with sediment concentration. The value of sediment concentration decreases as it approaches the surface and is larger at the bottom of the channel.
Meanwhile, [11] conducted a study to determine the size of the transported sediment grains against the current velocity in the waters of the Pawan River, Ketapang Regency. Water parameters that affect sediment deposition in the Pawan River meandering channel type. The study results obtained information on current velocity and grain size, which caused silting and narrowing of the river crosssection.
Based on that, a study was conducted on the Pondo Poboya River, a rainfed river. The Pondo Poboya River is one of the rivers that originate in the Parigi Regency. The research was conducted by observing field conditions and direct measurements in natural rivers with various parameters related to flow velocity, water depth, and sediment bed material. This river is the rainfed river. When the climate is rainy, the river has full of water along the river to the estuary. However, when the dry season, the water still flows until the middle part of the river, with varying water depths between 10 cm to 50 cm. The bedload sediment characteristics have unique behavior. Therefore, this research was conducted.

Materials and Method
The location of the research is the Pondo Poboya river which is in Palu, Central of Sulawesi. Administratively, the Pondo-Poboya River is located in Mantikulore District, Palu City, Central Sulawesi Province. Palu City is geographically located in the middle of Donggala Regency. Precisely  The research was conducted by collecting primary data. The primary data taken are the bedload sediment sampling, flow velocity, cross-sectional area of flow, and wet cross-sectional area of flow. Sediment bedload sampling was carried out in each part of the river, upstream, middle, and downstream. Each section is taken ten cross-sections. These 3 points are taken for each section, namely the crosssection's left, middle, and right sections. The picture below showed that the point of the bedload sediment sampling. Data collection of river cross-sectional area and river wet cross-sectional area is measured directly using the theodolite, meter gauge, and GPS. Because the flow depth varies, the velocity data collection and the measurement of the wet cross-sectional area of the flow are only carried out when there is water flowing. Sediment data collection was done manually using a shovel. The sediment taken is estimated to weigh 500 grams to meet the requirements of the grain gradation analysis. The sampling bedload sediment was carried out to Soil Mechanics Laboratory for analysis. The Soil Mechanics Laboratory was in Civil Engineering Faculty at Tadulako University, Palu. Perform sieve analysis testing in the laboratory that refers to grain size analysis (ASTM 422-63). Inspection of grain gradation using a set of sieves. The sediment data was sieved using a sieve and weighed. Then the results of sieving and weighing are entered into a graph to see the analysis of the gradation of sediment grains. Meanwhile, the velocity and the cross-sectional area data were used to analyze the friction factor using the equation of Manning, Raudkivi, Subramanya, and Meyer Peter Müller empirically.

Results and Discussion
Water depth is one of the variables that should not be forgotten in the geometric design/calculation of open channels. The effect of hydraulic changes on flow capacity is also primarily determined by the water depth factor. The roughness coefficient (n) will decrease when the water level and flow velocity increase. When the water depth is lower, the irregularity of the riverbed will stand out and the effect will be visible. Based on the measurement data in the field, the average water depth obtained at each location is shown in Table 1.
The water depth of the Pondo Poboya River has variated ( Table 1). Because of the dry season, the water depth variation is uneven flow. During the dry season, the river water flow is influenced by the riverbed porosity and roughness value. Comparing the water depth upstream of the river to the downstream showed that the further downstream, the lower the flow depth. This happens because the further downstream, the wider the wet cross-section, so the lower the flow depth. Source: Field measurement results (2020)

River-bed Slope Measurement
The riverbed slope measurement was done with GPS (Geographic Positioning System) along 7.6 km. This measurement represents the length of the river. When the morphology is straight, the measurement was taken 500 m interval. For the meandering morphology, the measurement was conducted at a 100 m interval. The table below shows the results of the riverbed measurement. The results of the measurement showed that the riverbed slope has a steep slope. It is because of the morphology of the river. This steep slope is due to meandering the river in certain parts and straight in other parts. When taking measurements in the field, it is difficult to determine whether meandering occurs in the shape of the river or the flow of water. This difficulty happens because when measuring, water only flows in the middle part of the cross-section of the river. When the river is straight as the same location the flow is meandering.

River Hydraulics Calculation
In this research, river hydraulics were calculated based on river discharge at each sampling location. The picture below shows the river cross-section sketch to calculate the river hydraulic parameter. The wet cross-area of the river that water flowing (Figure 3). For the part of the river that the water is not flowing, the cross area measure by meter gauge to know the morphology of the river area.  From the results of the calculation of each area of the river, the total area obtained is: The results of river hydraulics calculations at other locations can be seen in the following table The table above showed that as the further downstream, the width of the river is irregular. Usually, the further downstream, the wider the cross-section of the river. This condition is because the flow velocity slows down, and sedimentation occurs. The sedimentation will affect wider the cross-section of the river. In the Poboya river, sedimentation occurs in the middle part river. Because at the downstream river, there is a little part of water flowing. Sedimentation spreading around the middle part of the river.

Calculation of Bed Load Sediment Sieve Analysis
The sieve analysis test aims to obtain the size of the bedload sediment diameter (d50, d65, and d90). The bedload sediment materials samples to be tested were taken from twenty different cross-sections. The following is a table of test results:  And then, the results of gradation bedload sediments analysis make it to the graph to know the percentage of passed diametre of bedload at d50, d60, and d90.  And then, the results of gradation bedload sediments analysis make it to the graph to know the percentage of the passed diameter of bedload at d50, d65, and d90.  Figure 5, the grain size of the bedload sediment is obtained: d50 = 3 mm d65 = 5,5 mm, and d90 = 8,2 mm.  Figure 6. The grain analysis distribution downstream of the river The plot of the graph in Figure 6 showed that the grain size of the bedload sediment material is obtained: d50 = 2,2 mm d65 = 4 mm, and d90 = 7 mm.
The grain sediment distribution from the upstream of the river showed that the further downstream, the smaller the grain diameter. This condition is due to the lower water flow. The water depth along the river is getting lower. The water not flowing until downstream because the porosity of the bed river is high. The composition of sand indicates this in the middle, which is almost 90%.

Calculation of Roughness Coefficient
After testing the sieve analysis on the bed sediment sample, several methods of calculating the sediment roughness value are carried out to compare the roughness value. Manning Roughness Coefficient The results of the calculation of the roughness coefficient (n) for each location reviewed and the average coefficient on the Pondo-Poboya River are shown in Table 7 and Table 8.   Table 7 for sharing the review location shows that the minimum roughness coefficient is 0.0152 and the maximum roughness coefficient is 0.0478. In the Manning roughness formulation, the minimum roughness value is 0.02563. The maximum roughness coefficient is 0.0364, with an average value of 0.0310. When matched with the roughness coefficient value contained in the Manning table, this value is not much different, namely clean natural channels, straight, and clean winding.  Table 9 shows that the Manning formula has a better relationship than the other formulas. Therefore, Manning's roughness formula is suitable for the Pondo Poboya River.