Scour Countermeasures for Three-Sided Culverts

Bottomless (or three-sided) culverts use the natural channel bed and are environmentally attractive alternatives to traditional closed culverts. Moreover, they are often promoted as alternatives for replacing short bridges. These structures are typically founded (supported) on spread footings, and the issue of scour and the depth of footing must be addressed as part of their design. Many State highway agencies will not allow bottomless culverts unless they can be founded on solid rock formations. Therefore, there is a need to formulate a defendable procedure for estimating scour depths in other types of soil formations (e.g., sands). The scour problem is analogous to abutment and contraction scour in a bridge opening and can be treated in much the same manner.