| Abstract: | ABSTRACT: One hundred twenty-eight stream-crossing culverts in the central Oregon Coast Range were evaluated for peak flow capacity and were compared with current design guidelines. Their ability to pass the 25-year peak flow, as mandated by Oregon State Forest Practice Rules, and their maximum flow capacity were determined. Over 40 percent of the culverts were unable to pass the 25-year peak flow at a headwater to diameter ratio of 1. About 17 percent could not pass the 25-year peak flow without headwater overtopping the roadfill. Installing the next larger pipe size at an additional original installation cost of about 14 percent would have allowed nearly all these culverts to pass the 25-year peak flow. Culvert capacity varied with ownership and watershed size. |
