Many important insights into the dynamic coupling among climate, erosion, andtectonics in mountain areas have derived from several numerical models of the past fewdecades which include descriptions of bedrock incision. However, many questionsregarding incision processes and morphology of bedrock streams still remain unanswered.A more mechanistically based incision model is needed as a component to study landscapeevolution. Major bedrock incision processes include (among other mechanisms) abrasionby bed load, plucking, and macroabrasion (a process of fracturing of the bedrock intopluckable sizes mediated by particle impacts). The purpose of this paper is to develop aphysically based model of bedrock incision that includes all three processes mentionedabove. To build the model, we start by developing a theory of abrasion, plucking, andmacroabrasion mechanisms. We then incorporate hydrology, the evaluation of boundaryshear stress, capacity transport, an entrainment relation for pluckable particles, a routingmodel linking in-stream sediment and hillslopes, a formulation for alluvial channelcoverage, a channel width relation, Hack's law, and Exner equation into the model so thatwe can simulate the evolution of bedrock channels. The model successfully simulatesvarious features of bed elevation profiles of natural bedrock rivers under a variety of inputor boundary conditions. The results also illustrate that knickpoints found in bedrock riversmay be autogenic in addition to being driven by base level fall and lithologic changes.This supports the concept that bedrock incision by knickpoint migration may be anintegral part of normal incision processes. The model is expected to improve the current,understanding of the linkage among physically meaningful input parameters, the physicsof incision process, and morphological changes in bedrock streams.
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