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 densi-metric 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.