Culverts convey surface flow from one side of the roadway to the other. Culvert design comprises three general considerations: culvert size, location, and shape. The size of the culvert is directly related to the results of the hydrologic investigation. The location of the culvert is derived from the site geometry and comprises the alignment, length, and
slope. The site hydraulics and available roadway fill height (height of fill from creek bed to profile grade) are the controlling criteria for determining the shape of the culvert. However, shapes, sizes, and material types used for culvert construction can be precluded from use based on manufacturing limitations. Since only the site hydrology and geometrics are known and all other parameters are variable, a trial and selection process must be used to determine the appropriate culvert size and type.
