Building scour in floodplains

Scour of buildings or abutments in floodplains is considered using laborato ry experiments and a hydraulic approach. Based on a literature survey, the determining parameters are specified and the scaling parameters are selecte d 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 densimetri c particle Froude number has a significant effect on the scour pattern. The effect of sediment mixtures is particularly accounted for and a temporal s hift 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 de fined and compared with a large number of individual scour tests. Floodplai n scour may be significantly reduced by positioning a geotextile mattress a long the leading fronts of the building. A complete design procedure for th is novel method is presented, together with its limitations of applicabilit y.