Numerical Modeling of Sediment Transport using ANUGA Sed: Application to Mahanadi River Basin, India

Abstract

Soil erosion and sediment transport are natural processes primarily driven by water. However, excessive human interference through agriculture, urbanization, and the construction of water storage reservoirs has significantly impacted these processes. Human activities have altered the magnitude of soil erosion and deposition, leading to reduced water storage capacity in reservoirs, degraded water quality, and diminished agricultural yield. Therefore, it is crucial to analyze soil erosion and sediment transport dynamics within watersheds. This thesis focuses on modeling soil erosion using the Revised Universal Soil Loss Equation (RUSLE) approach and the sediment transport using the distributed model ANUGA. The modeling approaches were applied to the case of Mahanadi River basin in India. For modeling the soil erosion, which gives the potential soil loss in a catchment, the critical erosion index parameter is derived using the 30-minute rainfall dataset. Due to the unavailability of high-resolution rainfall data for historical events, rainfall intensity from IMERG satellite data was used along with gauge data with daily rainfall. The annual variations and spatial variations in sub-basins of Mahanadi River were simulated. The sediment transport was modeled using the ANUGA Sed model. The ANUGA Sed model is a two-dimensional hydrodynamics model based on shallow water equations, employs a finite-volume method. The model is capable of simulating large catchments in parallel mode on high-performance computing (HPC) systems. Through a series of numerical experiments, extensive tests and sensitivity analyses were performed for evaluating computational accuracy in terms of grid size, scalability and robustness in simulating flow and sediment transport. An extensive study of modeling the water flow and sediment transport was conducted for the Tel River sub-basin, involving serial and parallel simulations on both local and HPC systems. Further, in October 2023, field experiments were carried out on the Tel River to measure in-situ suspended sediment concentration at various sites. The numerical model simulation were compared with the field experimental observations. The ANUGA Sed model was subsequently applied for simulating the flow and sediment transport for the entire Mahanadi River basin using the Param Pravega and Param Porul supercomputing facilities developed by C-DAC to assess the model's performance and scalability in simulating sediment transport in a large river basin. In summary, the insights gained from this modeling study indicate the applicability of the ANUGA Sed model for simulating suspended load and riverine bed elevation changes due to bed load, which is useful to assess the impacts on flood prediction and the maintenance of navigational channel depths.