Influence Of Depot Size On Bed Load Transport Velocity Over Static Armour Layers

The influence of the amount of sediment deposited on a static armour layer on the transport velocity is presented. Tracer experiments were carried out in a 6m long, 0.3m wide and 0.4m high flume in the hydraulic laboratory of the Leichtweiss-Institut fur Wasserbau, Technische Universitat Braunschweig, Germany. The layer of bed material consisting of a sand-gravel mixture with grain sizes between 0.7mm and 31.5mm had a mean initial height of 12.5 cm. After an armour layer is fully developed, i.e. when the transport rate for a specific flow is negligible, coloured sediment with a grain-size of 3-5mm was placed on top of the bed surface. The size of the tracer bar varied between 1.1 and 4.4 kg. A functional relationship considering tracer mass, tracer grain size, travel time, transport distance, and shear stress to calculate the transport velocity is introduced.