Clear-water scour at bridge piers and abutments

Extensive studies on the temporal evolution of scour have been made recently at Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie (VAW), ETH Zurich, Switzerland, and models for scour estimation were presented. The VAW scour model is further investigated in the present study and possibilities for its refinement are identified. It is conceptualized that expression for temporal evolution of scour at bridge elements that is based on Froude’s similarity should more logically relate scour depth to the difference between actual densimetric particle Froude number and entrainment densimetric particle Froude number. The analysis of VAW data set on pier and abutment scour validates this concept. Also contrary to the previous assumption of a logarithmic increase in scour depth with time, the characteristics of ‘end scour’ is noticed to have been exhibited by a few of the VAW scour data on mixtures.