Modeling of erosion and design of structures for strengthening the Western Bug river banks

Abstract

The Western Bug River is a transboundary river in Eastern Europe. The average long-term water discharge in the studied section is 80.2 m3/s, and the spring flood with 1% probability is 818 m3/s. Retrospective analyses of aerial photography data for the period from 2004 to 2022 allowed us to establish the average annual bank movement rate, which was 0.85 m/year. A digital relief model of the catchment area was created and a detailed channel model was constructed, which is based on the use of low-water and Navier-Stokes equations. The calculations were carried out using the server computing equipment of BrSTU and allowed us to build a picture of the spatial and temporal patterns of the free surface levels of the flow, as well as the velocity field. The total spatial and temporal resolution of the model is 371,000 cells with 100–200 time intervals at 10–20 vertical grid layers. Toimplement the program, a programming language was selected that ensures efficient calculations and convenient interaction with the existing MIKE3 environment. As a result, Python/C++ was chosen, providing flexibility and high performance. The river sections exposed to the risk of erosion are identified, namely the coastal and coastal zone along the right bank in the area of the bend, both before and after it. The second section belongs to the floodplain zone, the flooding of which occurs during the spring flood corresponding to the maximum convergence of the meanders of the channel. The velocities obtained as a result of modeling do not exceed 2 m/s in the channel part. Areas at risk of erosion are highlighted. In the channel part, bank stabilization is recommended in the form of rock fill or stone paving. For the floodplain part near two meanders, it is necessary to provide for stabilization in the form of rock fill with a connecting structure for the passage of flood waters.