Scour at bridge sites is typically classified as contraction (or constriction) scour and local scour. Furthermore, avalanches and erosion from snowmelt can scour terrain of vegetation. Water passing through undersized culverts will scour away the surrounding soil over time. High winds scour away thin soils through erosion, as well as damage limbs and twigs. Water normally flows faster around piers and abutments making them susceptible to local scour. Culverts must be properly sized and installed, and protected from erosion and scour. This interpretation came to be known as the theory of Tidal scour. The Detour was a choice between Scrub or Scour. They are also used around bridges to prevent bridge scour. If the flow contracts from a wide floodplain, considerable scour and bank failure can occur. Limestone encased this sandstone to protect against scour and collision from watercraft. These charged molecules scour away surface imperfections, providing a pristine substrate. To ensure his survival, he manipulates the Titans to scour the realms. This manual includes several techniques of estimating scour depth. The Saxon people scour the White Horse free of weeds, keeping it white and visible.