极端气象水文条件下滨海地区小流域溃坝洪水模拟及风险评估

Simulation and Risk Assessment of Dam-break Flood at Small Coastal Watershed Under Extreme Hydrometeorological Conditions

极端气象水文条件下的小流域水库溃坝,往往造成更为严重的洪水风险。为分析滨海小流域溃坝洪水风险,以粤港澳大湾区滨海小流域为例,基于二维溃坝洪水演进模型和洪水风险分级方法,探究小流域洪水淹没过程和风险分区,及极端降水和风暴潮影响下的变化响应。结果表明,溃坝洪水快涨慢退,主要敏感点约在17.5~22.0min之间达到最大淹没水深,退水时间约为6h,淹没范围占48.9%,以中、高风险区为主。极端降水和风暴潮对洪水涨退水规律影响较小,但对主要敏感点的最大流速和最大淹没水深影响较大。百年一遇极端降水叠加风暴潮,主要敏感点的最大流速、最大淹没水深分别增加了23.8%~39.9%、10.7%~31.4%,其中风暴潮贡献分别为8.3%~14.9%、4.7%~14.4%。极端降水使得洪水淹没范围扩大且风险等级上升,而风暴潮对风险区范围和等级影响较小,仅使临近海岸局部地区的风险等级有所上升。研究结果可为滨海地区中小型水库洪水溃坝风险管理提供参考。

Under extreme hydrometeorological conditions,dam-break of small watershed reservoir often leads to more severe flood risks.This study focused on dam-break flood risk of coastal small watershed in the Guangdong-Hong Kong-Macao Greater Bay Area.By employing two-dimensional dam-break flood routing model and flood risk classification method,the flood inundation process and risk zoning were investigated,as well as the response to their changes under ex-treme precipitation and storm surge.The results show that the dam-break flood rises rapidly and recedes slowly,with the main evaluated locations reaching the maximum submergence depth between 17.5 and 22.0 minutes,and the recession time being about 6 hours.The inundation area accounts for approximately 48.9%,predominantly in medium and high-risk zones.Extreme precipitation and storm surges have a relatively small impact on the pattern of flood rise and fall,but have a significant impact on the maximum flow velocity and maximum submergence depth of the main evaluated loca-tions.With a 100-year extreme precipitation event combined with storm surge,the maximum flow velocity and maximum submergence depth of the main evaluated locations increased by 23.8%to 39.9%and 10.7%to 31.4%,respectively.The contribution of storm surges was approximately 8.3%to 14.9%and 4.7%to 14.4%,respectively.Extreme precip-itation expands the inundation area and raises the risk level,while storm surge has minimal impact on the range and level of risk zones,only slightly increasing the risk level in some areas near the coast.The research results can provide refer-ence for flood dam-break risk management of small and medium-sized reservoirs in coastal areas.