Scour around structures in tidal flows

Abstract

This report describes a laboratory study carried out at HR Wallingford to investigate scour development around obstructions that are large in relation to the flow depth of a design procedure to determining scour depths. The tests were performed to assess the influence of the following parameters: reversal of the flow direction, tidal cycle duration, water depth, shape of the obstruction and sediment size. The experimental facility used in the study was a 24m long flume by 0.6m width fitted with an axial pump that allowed reversal of the flow direction. The test section was formed by a 4m long granular mobile bed where typical structures were placed. Preliminary tests were performed to measure scour development in unidirectional flows in order to allow later comparisons with tidal flow conditions. The work described in this report was partly funded by the Construction Directorate of the Department of the Environment, Transport and the Regions.