Morphological Evolution of Dune-Like Bed Forms Generated by Bridge Scour

Abstract

This research intends to provide new insights on sediment transport at bridges, exploring the features of migrating dune-like bed forms generated immediately behind piers or abutments by local scour processes. An extended VAW (Laboratory of Hydraulics, Hydrology, and Glaciology, Swiss Federal Institute of Technology Zurich) data set collected from 1999 to 2002 was analyzed. In total, 63 temporal runs involving 480 observations for cylindrical piers, and 54 runs with 384 observations for rectangular-shaped abutments were considered. It was found that the main dimensionless parameters governing the dune processes are the relative pier diameter (or abutment width), densimetric Froude number, wash-out parameter, and relative time. The dune height is mainly controlled by the relative width of the scour element, and its relative length depends on the wash-out parameter. The morphologic dune evolution and its downstream propagation are described using straightforward equations as a function of the key parameters. The results apply to practice and are suitable to assess the performance of computational modeling.