Bridge Pier Scour with Debris Accumulation

Laboratory data, showing the effect of simulated floating debris accumulation at bridge piers on the local scour depth, are presented. The experiments are conducted using idealized impermeable cylindrical debris shapes attached concentrically to a cylindrical pier. The maximum scour depth recorded is 3.6 times the pier diameter. The design method proposed by Melville and Sutherland in 1988 is shown to predict the maximum possible local scour for a pier with simulated floating debris accumulation provided that an effective pier width is substituted for the actual pier width. The effective pier width is calculated as a weighted average of lengths (vertical dimension) of the debris and exposed pier.