Building scour in floodplains

Scour of buildings or abutments in floodplains is considered using laboratory experiments and a hydraulic approach. Based on a literature survey, the determining parameters are specified and the scaling parameters are selected such that the Froude similarity law applies. A scour equation in terms of time is developed by accounting systematically for the effects of approach flow, granulometry and building geometry. It was found that the densimetric particle Froude number has a significant effect on the scour pattern. The effect of sediment mixtures is particularly accounted for and a temporal shift from the mean grain size at the start of scour, to the 90% grain size for developed scour is formulated. The accuracy of the scour equation is defined and compared with a large number of individual scour tests. Floodplain scour may be significantly reduced by positioning a geotextile mattress along the leading fronts of the building. A complete design procedure for this novel method is presented, together with its limitations of applicability.