One‐dimensional numerical modeling of sediment transport and bed deformation in open channels

Abstract

[1] A one-dimensional numerical model for simulating unsteady flow and sediment transport in open channels is presented and tested. The flow hydrodynamics is represented by the shallow water equations, and the bed morphodynamics is represented by the Exner equation and an additional equation describing the nonequilibrium sediment transport. Sediment size distribution is represented by the median grain diameter and the standard deviation, instead of the usual modeling with multiple particle size classes. Various methods for computing bed elevation changes at a cross section due to erosion or deposition of sediment are proposed and tested, including an innovative approach that relates the spatial pattern of erosion and deposition rates to boundary shear stress distribution, which is calculated by the Merged Perpendicular Method. An explicit finite difference scheme is employed for solving the water and sediment governing equations. The pertinence of the model is examined for two hypothetical cases. The model is then tested on one set of laboratory experiments on bed degradation under steady flow, showing excellent model data fit, and indicating that incorporating a nonequilibrium sediment transport equation into the model structure is an important element in reproducing the bed degradation process. Finally, the model is applied to simulate the morphological changes taking place in the Ha!Ha! River (Quebec) after the failure of the Ha!Ha! Dyke on July 1996. Relevant results can be obtained in terms of changes in longitudinal bed profile and cross-sectional geometry as well as water levels, although some discrepancies are obtained between the simulated and surveyed cross-sectional geometries, mainly because bank failure and channel widening are not modeled.

Numerical modelling of climate change impacts on Saint‐Lawrence River tributaries

“…1D morphodynamic models are conceptually inferior to 2D or 3D models which can resolve local spatial differences in fl ow strength, but higher-dimension models based on the St-Venant or Navier-Stokes fl ow equations are still computationally too expensive for long-term morphological predictions over extended reaches (Kleinhans et al, 2008;El kadi Abderrezzak and Paquier, 2009). Rule-based 2D cellular models, which are computationally far more effi cient, can generate plausible generic behaviour (Murray and Paola, 1994) and have been used to simulate the long-term (Holocene) behaviour of specifi c river systems (Coulthard et al, 1999;, but they have not yet been shown to yield quantitatively accurate predictions of sediment transport and channel change in specifi c situations.…”

Numerical simulation of the dynamics of sedimentary river beds with a stochastic Exner equation

“…They have correctly predicted useful information such as an approximation of the total mass of sediments transported during a flood. Among other examples, [13] shows that with a one dimensional sediment transport model, they achieve reasonably good results in reproducing the bed changes due to a large flood event on the Ha!Ha! River (Canada).…”

Hydrology, sediment circulation and long-term morphological changes in highly urbanized Shenzhen River estuary, China: A combined field experimental and modeling approach

“…Under such circumstances, numerical models can be used as a supplementary tool in analyzing the long-term processes. Attempts to investigate the sediment transport and morphological processes with numerical models have been made in a variety of studies of different time scales (for example, see Cao et al, 2002;Wu, 2004;El kadi Abderrezzak and Paquier, 2009;Chen et al, 2010;Zhang and Duan, 2011;among others). These models, sometimes called ''process-based" models because they solve coupled systems of hydrodynamic equations and sediment transport equations, successfully reproduced the fluvial processes in event-based simulations.…”