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Abstract: The paper introduces a 2D shallow water model based on a two-phase formulation for the analysis of fast geomorphic transients occurring in the context of river morphodynamics. Mass and momentum conservation principles are separately imposed for both phases. The model naturally accounts for non-equilibrium solid transport, since neither instantaneous adaptation hypothesis nor any lag equation is employed to represent sediment dynamics. The hyperbolic character of the proposed model is shown to be preserved independently on the flow conditions. Results from numerical simulations of both 1D and 2D test-cases are compared with literature experimental data and with available numerical solutions. [Copyright &y& Elsevier]

Abstract: Our goal is to develop a model capable to discern the response of a watershed to different erosion mechanisms. We propose a framework that integrates a geomorphic component into the physically-based and spatially distributed TIN-based Real-time Integrated Basin Simulator (tRIBS) model. The coupled model simulates main erosive processes of hillslopes (raindrop impact detachment, overland flow entrainment, and diffusive processes) and channel (erosion and deposition due to the action of water flow). In addition to the spatially distributed, dynamic hydrologic variables, the model computes the sediment transport discharge and changes in elevation, which feedback to hydrological dynamics through local changes of terrain slope, aspect, and drainage network configuration. The model was calibrated for the Lucky Hills basin, a semi-arid watershed nested in the Walnut Gulch Experimental Watershed (Arizona, USA). It is demonstrated to be capable of reproducing main runoff and sediment yield events and accumulated volumes over the long term. The model was also used to study the response of two first-order synthetic basins representative of landforms dominated by fluvial and diffusive erosion processes to a 100-year long stationary climate. The analysis of the resultant slope-contributing area relationships for the two synthetic basins illustrates that the model is consistent with assumed principles of behavior and capable of reproducing the main mechanisms of erosion. [Copyright &y& Elsevier]

Abstract: This paper presents a three-dimensional (3-D) numerical model to simulate morphological changes in alluvial channels due to bank erosion. A method for the simulation of bank erosion is established. This is incorporated into a 3-D mathematical model for turbulent flow and non-uniform, non-equilibrium sediment transport. This model is applied to simulate morphological changes in the Shishou bend of the middle Yangtze River in China, where serious bank erosions occurred during the last two decades. The double-layer sediment structure of the riverbank on the middle Yangtze River is taken into account in the bank erosion module. Both cohesive and non-cohesive bank material in the different layers are considered. The bank erosion module also includes other factors affecting the rate of bank erosion, such as the longitudinal length of failed bank, the thickness of each layer in the double-layer structure, and the erosion-resisting effect of cohesive material from the top layer of failed bank. A locally-adaptive grid system is proposed to efficiently simulate the lateral migration of alluvial channel due to bank erosion. The predictive capability of the 3-D model is examined by laboratory data. Simulated processes of bank erosion agree with field observations in the Shishou bend during the period of October 1996–October 1998, and the bank erosion module plays a significant role in simulating morphological changes of the study reach. In addition, the equivalent channel-forming discharge, which is defined as a constant discharge that can create the same amount of bank erosion in an alluvial channel as that created by natural runoff processes during the same period of time, is proposed to improve calculation efficiency for feasibility studies. [Copyright &y& Elsevier]

A coastal area morphodynamics model was developed which is capable of modelling both short-term and long-term bathymetric changes in coastal areas. The model is composed of three main modules: wave transformation module, hydrodynamic module and sediment transport and morphology module. The three main modules run simultaneously where the waves and coastal currents information are passed to the sediment transport module, which calculates the sediment transport fluxes and the corresponding bathymetric changes. The model''s output is linked through dynamic plotting libraries, which produces contour plots, vector plots and animation files for the waves, currents, sediment transport fluxes and bathymetry. The model''s output compares very well with other commercial models for the case of an offshore breakwater over a sloping beach. [Copyright &y& Elsevier]