The 24th IAHR-APD Congress (24th IAHR-APD Congress)

246 / 2024-02-28 16:03:04

Hydrodynamic Analysis of Flash Flood Disaster in Zanhuang, Hebei Province

Extreme rainfall, flash floods, rapids, high-speed washout

In July 29^th, 2023, Extreme rainfall happened in Hebei Province. The rain water induced flash flood in Zanhuang, a country of Hebei province. Based on the runoff calculation results, the 7.29 flood process was inverted, and the 10-year, 20-year and 50-year design flood processes were analyzed by hydraulic models. (1) The magnitude of the 7.29 flood was between 10 and 20-year return times in terms of peak flow, but due to the uneven rainfall, the peak flow in some sub-areas has exceeded the 20-year return design peak flow. (2) The overall slope of the Huaihe River is steep, and there are many alternating sub-critical and super-critical slow flow pattern sections. The relationship between the upstream and downstream water levels is complex. When building some sand dams, hinge dams and other blocking facilities, it is recommended to combine the upstream and downstream flow conditions to design the project scale and formulate dispatching principles to avoid excessive congestion during flood periods. (3) The upstream section of the Baicaoping Reservoir, the Huaihe River is a mountainous river channel with a steep riverbed slope and strong flow capacity. The difference in inundation range under different design floods is small. Only a small area is affected by flood inundation; however, the flood flow velocity is high. Damage to embankments and bridges along the coast is mostly caused by high-velocity water and sand erosion. More attention is needed to be paid on anti-scouring design. (4) The downstream of Baicaoping Reservoir lies in a transitional area from a mountainous river to a plain river. Although the slope has slowed down and the width of the flow section has increased, the overall flow velocity is still large, and attention must be paid to anti-scouring design.