CSDMS 2011 annual meeting poster Alan Kasprak

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Presentation provided during CSDMS annual meeting 2011

Modeling Gravel Bed River Morphodynamics Using a Step-Length Based Approach

Alan Kasprak, Utah State University Logan Utah, USA. akasprak@aggiemail.usu.edu
Joseph M. Wheaton, Utah State University Logan Utah, United States. joe.wheaton@usu.edu


Understanding gravel bed river morphology over decadal to centennial timescales is vital to making informed stream management and restoration decisions. Factors such as land use change and climate shifts over such timescales may drastically alter river evolution – with major implications for in-channel and riparian habitat. Given these longer timescales of influence, field-based studies may be unable to fully capture such morphologic shifts. Scenario-based morphodynamic modeling is emerging as a means of quantifying gravel bed river evolution, yet current models are unable to predict changes in stream morphology over the timescales in question and with adequate spatial resolution, a problem due largely to the computational overhead they require. Since the computational overhead required to drive sediment transport has hindered previous modeling efforts, field-based research suggests a potential improvement, in that sediment is often mobilized downstream with characteristic step-lengths. Here we introduce a morphodynamic model which drives sediment transport using a step-length based approach. Such a technique negates the need for frequent recalculation of sediment dynamics in the flow, and correspondingly reduces computational overhead. Upon application of this model to the River Feshie (UK), we observe that it accurately reproduces many bed morphologies observed during annual high-resolution topographic surveys. By employing step-length based sediment transport distributions, the formation and preservation of bed morphologies can be accurately predicted with less computational overhead than was available in previous morphodynamic models. Using this new model, a better understanding of gravel-bed river morphodynamics over longer-term timescales (decades to centuries) may aid in the management of gravel bed streams under shifting discharge and sediment regimes.

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