Sediment Transport Modeling using HEC-RAS 1D

All rivers conveying water contain sediment particles in any of the three forms: bed load, suspended load, and wash load. Natural and human factors trigger rivers to undergo severe deposition and erosion of beds or banks (Joshi et al. 2019). The long-term effects of erosion and sedimentation cause changes in river geomorphological regime. The sediment transport process in rivers depends on several factors including sediment particle size, catchment characteristics (area, basin slope, river slope, and channel width), catchment’s land cover, climate changes effects and flood events.

To simulate the realistic hydraulic and sedimentation phenomena, several numerical models have been developed over the past decades. Among them, 1D numerical models are still successfully used for long river reaches due to simple computations, small amount of required input datasets, and short computation time (Werner, 2001; Horritt and Bates, 2002; Panin and Jipa, 2002). Due to the high capability of the HEC-RAS 1D model for hydraulic simulation and analyzing the sediment transport process, several companies, engineers, and researchers, all around the world, are using the HEC-RAS 1D model in different projects. Sediment computations in HEC-RAS utilize one-dimensional, cross-section averaged, hydraulic properties from RAS’s hydraulic engines to compute sediment transport rates and update the channel geometry based on sediment continuity calculations.

An HEC-RAS sediment model requires a geometry file (in 1D case we need cross-sections), a flow file (quasi-unsteady or unsteady flow hydrograph), a sediment data file (including bed gradation, transport function, fall velocity, Sorting method, and boundary conditions), and a sediment analysis plan file. In this applied course, the details of sediment transport modeling in HEC-RAS are described completely with a applied examples. After finishing this course, the user can easily simulate the sediment transport process for each real case study and project.