Scour at cofferdam structures on river walls

Construction activities in rivers and estuaries require cofferdams to be installed to provide a dry working area. Predictions of scour at these temporary structures are made using methods proposed for river abutments in industry guidance with engineering judgement made on the selection of coefficients. The area of the cofferdam and protrusion in the waterway is often larger than the permanent works they are facilitating and they are long, in some instances several hundred metres along the flow direction. Clear-water scour experiments in the General Purpose Flume at HR Wallingford explore the influence of wall mounted cofferdam shape and length, water depth and flow speed on scour. The results provide information of use to engineers working with cofferdams and comments are made on the application of predictive methods.