In a transportation context this refers to drainage structures such as bridges or culverts. The purpose of hydraulic design is to ensure structures are of sufficient size that natural flooding is not worsened and to ensure that the structure can withstand the design flood and remain traversable. This is required in order to protect the property and residents upstream and downstream of a highway structure and any motorists who use the roadway. Hydraulic designers also must account for scour. Scour refers to the tendency of soil in a streambed to be washed away by flowing floodwaters.
Earth is a world of water.
Roughly three quarters of this planet is covered by water. The interaction between the sun and the water is the force behind life on this planet. Rain, falling one drop at a time, can produce tragic results. Since 1990, nearly all presidentially declared disasters in Tennessee involved precipitation of some kind. Most have involved flood damages.