Scour in Bottomless Culverts

J. Sterling Jones

Laboratory experiments were conducted at the FHWA Hydraulics lab to determine how deep footers would have to be set for natural bottom culverts. Local scour at the upstream corners of these culverts is analogous to abutment scour at a bridge. An analytical procedure has been developed that is based on estimating the local unit discharge in the vicinity of the culvert walls and predicting a local equilibrium flow depth needed to sustain that unit discharge. Experimental results were used to derive an amplification factor that accounts for vorticity and other secondary currents that are caused by sudden mixing at the upstream corners of the culvert.