A one-layer model to predict the time development of static armour

The development of static armour has been studied extensively from a number of different points of view. Given the hydraulic conditions and the initial composition of the bed, many relations have been proposed which predict the armoured distribution which develops. There are fewer relations which predict the development of the armour layer in time and the change in transport rate as the armour develops. An attempt is made in this paper to use a simple, one-layer model to predict the development of static armour and a comparison is presented with results obtained using different transport formulae for non-uniform sediments. It is shown that a simple model based on the propagation of kinematic waves can predict the development of self-armoured beds by simulating the variations in sediment transport rate at the downstream end of a laboratory flume and in predicting the composition of the static armour that is produced.