Flood Risk Assessment in the Loess Plateau: A Case Study of the Quchan Basin, China

The Loess Plateau is highly vulnerable to floods and landslides. This paper aims to assess the flood risk in the Quchan River basin located east of the Loess Plateau. A FloodArea model developed by the Gemer company of Germany is seamlessly integrated with ArcGIS in a module form. The principle is based on a two-dimensional unsteady hydrodynamic model, and the calculation is based on a hydrodynamic method. Although rare in history, heavy precipitation struck the Quchan River basin from 4 August to 7 August 2020. The DEM (Digital Elevation Model), roughness, and hourly rainfall in the basin were used to run the FloodArea model. Under the rainstorm scene, an hourly flooding pattern was simulated at a 30-m high resolution. Moreover, land-use types were converted to roughness values because different land-use types have different roughness values. Results show that a flash flood risk is higher in low-lying river areas and gullies of the Quchan River basin than other areas. During this flooding, the maximum flooding depth at the survey site was 3.1 m, close to the observed flooding depth. For the disaster situations of the simulations, the population affected by the flood was 5475, the GDP was 36.15 million Yuan, as well as the disaster areas of cultivated and residential lands, were 20.7 and 0.7 km², respectively. The affected GDP and land area were consistent with the disaster-related data collected from the survey, but the affected population was lower than those reflected in the survey were. This indicates that the FloodArea model is superior in simulating flooding situations and can be employed in the risk evaluation and early warning of rainstorm and flood disasters in the Quchan River basin.