The arrested gravel front: stable gravel-sand transitions in rivers Part 2: General numerical solution

Many rivers have an abrupt transition from gravel-bed to sand-bed morphology. In many cases the point of transition is neither prograding nor retrograding, but is rather arrested in place. Two mechanisms are hypothesized as responsible for stabilizing the gravel-sand transition, basin subsidence (or alternatively base level rise) and abrasion of gravel. The companion paper offers a simplified analytical solution for the long profile of a river with such a transition. This treatment allows for direct insight into the relation between the morphology and the controlling mechanisms at the expense of several gross approximations. The present paper offers a rigorous complete numerical solution which takes such facts as the streamwise sorting of heterogeneous gravel into consideration.