Modelling of the Alpenrhein delta in lake of Constance

The Alpenrhein river has been artificially extended into Lake Constance by lengthening its levees. The purpose of a planned additional extension is to prohibit the premature sedimentation of the bays surrounding the alluvial delta. The current investigation addresses the question how a part of the flow and transported sediment can be diverted through levee breaches in a controlled manner during floods. The breaches would then lead to a more natural delta development. These processes were studied with hydraulic and 2-d numerical models. The sediment in the hydraulic model consisted of expandable polystyrene grain material with a density of
1030 kg/m3, a density far smaller than the prototype sediment (Lightweight Model). The horizontal model scale was 1:70 and the vertical scale was 1:32, such that the model was geometrically distorted by a factor of approximately 2.2. Only the sand portion of the total suspended sediment load was modeled. The bed material of the Alpenrhein channel extension and the most important depositis on the lake side of the levee breaches are sand.