Linked Canyons and Fans Communicate Through a Migrating Bedrock‐Alluvial Transition

Abstract Net‐erosional fluvial landscapes are often treated separately from net‐depositional fluvial landscapes. Yet these landscapes are often tightly linked by means of a moving‐boundary bedrock‐alluvial transition. We consider a linked canyon‐fan system in a Basin and Range province, basing our work loosely on Rainbow Canyon and Panamint Valley, USA. The canyon is mixed bedrock‐alluvial upstream, and incises into a plateau undergoing uplift. The fan is purely alluvial, and is part of a bajada in the adjacent valley undergoing subsidence. It might be thought that uplift would push the bedrock‐alluvial transition out to the canyon mouth. Yet this transition is often observed to be well up the canyon itself. Here we show that this does not necessarily indicate that the region is tectonically quiescent. The migration of this transition can be explained in terms of canyon‐fan interaction captured by a single, dimensionally homogeneous morphodynamic model which folds in alluvial and incisional processes.