考虑Copula-LM-HMS耦联的台风情境下大坝洪水漫顶风险率计算

Calculation of Dam Flood Overtopping Risk Rate under Typhoon Scenario Considering Copula-LM-HMS Coupling

气候变化下台风风暴潮出现频次增加,形成的暴雨洪水对水库大坝安全产生极大威胁。由于部分地区实测流量资料缺少,基于雨量资料的随机模型与水文模型耦合模拟洪水过程线的研究亟待发展。针对现有小流域流量资料缺少问题,研究了基于降雨随机模型与水文模型的Copula-LM-HMS耦联模型,来模拟入库洪水并计算水库大坝洪水漫顶风险率。该模型通过Copula函数与拉丁超立方-蒙特卡罗抽样(Latin Hypercube-Monte Carlo Simulation)生成流域多组7日降雨数据,并通过变倍比放大法缩放处理得到相应降雨序列,利用HEC-HMS水文模型模拟洪水过程线并结合调洪演算得到坝前最高水位,同时考虑风浪作用来模拟台风情景下的库水位变化情况,计算大坝洪水漫顶风险率,并分析不同组合条件对洪水漫顶风险率的影响。余姚市四明湖水库实例分析表明,构建的Copula-LM-HMS耦合模型计算得到的拦河坝在未来台风情境下无漫顶风险,自溃坝最小漫顶风险为0.22%,最大漫顶风险达到2.68%;洪水漫顶风险与降雨分布及起调水位有关,同时风浪作用对洪水漫顶风险影响较大。基于耦合模型进行中小流域洪水漫顶风险率计算,不仅能考虑降雨系列之间的相关性、流域地形特征与实际调洪规则,还可延长无流量资料地区水库大坝应对台风情境下洪水风险的预报期,为保证水库大坝应对未来气候变化影响下的运行安全提供参考。

The frequency of typhoon storm surge increases under climate change,resulting in rainstorm and flood,which poses a great threat to the safety of the reservoir dam.Due to the lack of measured flow data in some regions,research on coupling stochastic models based on rainfall data with hydrological models to simulate flood hydrogr-aphs urgently needs to be developed.In response to the lack of flow data in existing small watersheds,a Copula-LM-HMS coupled model based on rainfall stochastic model and hydrological model is studied to simulate inflow floods and calculate the risk rate of reservoir dam flood overtopping.This model generates multiple sets of 7-day rainfall data in the watershed through Copula function and Latin Hypercube Monte Carlo Simulation.The corresponding rainfall sequence is obtained by scal⁃ing and processing by using the zoom ratio method.The HEC-HMS hydrological model is used to simulate the flood hydrograph and com⁃bined with flood routing to obtain the highest water level in front of the dam,while the effect of wind and waves are considered to simulate the changes in reservoir water level under typhoon scenarios.The risk rate of dam flood overtopping is calculated and the impact of different com⁃bination conditions on the risk rate of flood overtopping is analyzed.The case study of Siming Lake Reservoir in Yuyao City shows that the constructed Copula-LM-HMS coupling model calculates that the barrage has no overtopping risk in the future typhoon scenario,with a mini⁃mum overtopping risk of 0.22%for self breaking dams and a maximum overtopping risk of 2.68%.The risk of flood overtopping is related to the distribution of rainfall and the starting water level,and the effect of wind and waves has a significant impact on the risk of flood overtop⁃ping.The calculation of flood overtopping risk rate in small and medium-sized watersheds based on coupled models can not only consider the correlation between rainfall series,watershed terrain characteristics,and actual flood regulation rules,but also extend the prediction period for reservoir dams in areas without flow data to cope with flood risks in typhoon scenarios,providing a reference for ensuring the operational safety of reservoir dams in response to future climate change impacts.