Influence of Culvert Shape on Outlet Scour

A flume study is conducted to determine culvert shape influence on the scour geometry at culvert outlets. Twenty-six experiments are performed in which flows discharged for 316 minutes through circular, arch, square and rectangular shaped culverts and the resulting scour holes are documented. The scour hole dimensions for the arch, square and rectangular shaped culverts are normalized and compared to the scour hole dimensions for the circular culvert. Culvert shape significantly influenced the scour dimensions compared to the scour dimensions determined using the circular shape culvert. A series of expressions are developed correlating the dimensionless scour hole parameters of depth, width, length and volume to the modified discharge intensity. The denominator of the modified discharge intensity parameter, termed the culvert shape factor, compensates for shape differences for comparison.