Author(s): Edom M. Moges; Jeff A. Tuhtan; Habtamu G. Tolossa
Keywords: No Keywords
Abstract: Channel planform, pattern, morphology, erosion, deposition are to a large extent determined by the amount of sediment transported by the flow. Engineering applications such as channel stability, reservoir sedimentation and bridge pier scouring rely on knowledge of the transport processes for design, management and maintenance. In order to analyze these processes, the use of different numerical models is often indispensable. Sedimentation and River Hydraulics Two–Dimensional model, SRH-2D is a depth-averaged numerical model using the finite volume method on a hybrid meshes. Sediment transport in this model can be computed using four different equations which have been developed for different bed conditions. Here the applicability of the implemented four sediment transport equations for a gravel bed river reach on the River Sp? l in Switzerland is evaluated and the sensitivity of the best predicting equation to the different parameters is established. The model results show that of the four sediment transpor equations tested, the equation developed for sandy rive beds by Engelund and Hansen (1972) results in the larges discrepancy with field measurements. The Parker (1990and Wilcock&Crowe (2003) equations show comparably similar results. The Meyer-Peter and Muller (1948equation modified by Wong and Parker (2006) (MPM gives the most satisfactory results compared to the field measurements. The sensitivity of the MPM equation when estimating of erosion and deposition was tested using different active layer thickness values and available adaptation length equations. Additionally, the effect of Manning’s roughness coefficient on estimations of the bed shear stress is also carried out. The calculated values of the erosion depths are dependent on the chosen active layer thickness, where it was observed that only marginal change occurs for only the lower range of thickness values. The selection of adaptation length equations has a large impact on the spatial distribution of erosion and deposition areas. Further, it is proven that calibration of Manning’s roughness value has a high correlation to bed shear stress estimates. It is well known that bed shear stress, velocity, sediment particle size and channel cross section are critical parameters governing sediment transport.