Bridge abutment scour: estimation and protection

Abstract

A comprehensive method for estimating local scour depths at bridge abutments is presented. The method was developed in New Zealand on the basis of an extensive series of laboratory investigations. Application of the method ensures that the various influences on local scour depths are systematically addressed. These are the characteristics of the flow approaching the bridge crossing, the shape of the river channel in the vicinity of the bridge, the characteristics of the bed sediments in the vicinity of the bridge, the geometry of the bridge abutments, and the peak value and duration of the design flood. Application of the method is highlighted.Preliminary results from a current investigation of the use of riprap and cable-tied blocks to protect bridge abutments are presented. The experiments apply to spill-through abutments sited on the flood-plain of wide river crossings, and wing-wall abutments sited near the bank of narrow crossings.