Abstract
In 2018, a flash flood occurred in the Zhongdu river, which lies in Yibin, Sichuan province of China. The flood caused many casualties and significant damage to people living nearby. Due to the difficulty in predicting where and when flash floods will happen, it is nearly impossible to set up monitors in advance to detect the floods in detail. Field investigations are usually carried out to study the flood propagation and disaster-causing mechanism after the flood’s happening. The field studies take the relic left by the flash flood to deduce the peak level, peak discharge, bed erosion, etc. and further revel the mechanism between water and sediment transport during the flash flood This kind of relic-based study will generate bigger errors in regions with great bed deformation. In this study, we come up with numerical simulations to investigate the flash flood that happened in the Zhongdu river. The simulations are based on two-dimensional shallow water models coupled with sediment transport and bed deformation models. Based on the real water level and discharge profile measured by a hydrometric station nearby, the numerical simulation reproduced the flash flood in the valley. The results show the flood coverage, water level variation, and velocity distribution during the flood. The simulation offers great help in studying the damage-causing process. Furthermore, simulations without considering sediment transport are also carried out to study the impact of bed erosion and sedimentation. The study proved that, without considering bed deformation, the flood may be greatly underestimated, and the sediment lying in the valley has great impact on flood power.
Highlights
Mountainous areas take up 75% of the world’s land
The inlet discharge is based on the discharge profile monitored by the hydrometric station near CS20
Squared Error (Error (RMSE) between the simulated discharge and monitored discharge for each case is listed in Table 2. and it presents that the discharge profile could be similar after a 14 km long flow and sediment transport
Summary
Mountainous areas take up 75% of the world’s land. In Europe there have been 1,564 flood events (1870–2016), of which 879 (56%) were flash floods, 606 (39%) were river floods, 56 (4%) were coastal floods, and the remaining 23 (1.5%) were compound events (Paprotny, et al, 2018). To study the flood in detail, many researchers simulated the flash flood with depth-averaged two-dimensional hydrodynamic models, which is a comprising tool to capture the flow dynamic behavior and save computational time for spatially large-scale flow domains (Guan, et al, 2016; Liu, et al, 2020). These models solve the full governing equations, including rainfall and infiltration sections. All these data contribute to the numerical inversion of the flash flood
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