黄河悬河段城市洪灾过程模拟及风险动态评估研究——以开封市为例

The Yellow River is well-known for its disastrous features due to serious sedimentation, easy dyke-failure, and frequent migration. In recent years, the lower Yellow River is facing high flooding risk due to the increase of extreme weather events and natural disasters. The hanging river near Kaifeng is one of potential sections with high risks of dyke-breakage and flooding. Therefore, this study is taking Kaifeng City as a case study. It aims to investigate the characteristics of flooding system and its evolution in urban areas along the hanging Yellow River by combining hydrodynamic models and GIS/RS technology. It will simulate the potential dyke-failure and the dynamic advancing process of urban flood with MIKE model. To integrate the impact of sedimentation, HEC6 model will be used to calculate the sediment transport. Based on these simulations, a dynamic model for flood risk assessment will be established. With the scenario analysis technique, the response of future flood risk and dynamic assessment of flood risk along the lower Yellow River will be analyzed. The assessment method and procedures for flood risk will be constructed and the flood risk zoning will be made for better flood risk management. This project will implement the multi-disciplinary method and integrate the technology to simulate the urban flood process. The results from this project will not only improve the development of urban flood risk assessment theory, but also provide a solid scientific foundation for urban planning and flood control strategies in Kaifeng and other similar area along the Yellow River.

黄河自古以来就是善淤、善决、善徙的多灾河流。近年来，黄河下游悬河段面临十分严峻的洪灾决溢风险，据相关研究开封河段是未来50年内黄河下游决溢改道潜在危险的重点河段之一。本研究以开封市为实证区，综合运用水动力学模型与地理信息系统耦合；分析黄河悬河段城市洪灾系统结构特征及洪灾风险演变规律；运用MIKE模型进行溃堤分析和城市洪水演进动态模拟，考虑泥沙淤积的影响，采用HEC6模型进行输沙演算，建立洪灾风险动态模拟模型；采用情景分析技术，分析洪灾风险动因响应关系；构建洪灾风险动态评估方法和程序，对洪灾风险进行区划，提出风险管理策略；这不仅可以丰富城市洪灾过程与风险评估基本理论，而且还为开封市及其它沿黄城市制定城市发展规划和防洪减灾应急管理提供科学依据。

黄河下游是举世闻名的“地上悬河”，自古就具有善淤、善决、善徙的特点，洪水灾害历来为世人所瞩目，历史上被称为中国之忧患。随着全球气候变化所引起的降水异常、自然灾害增加以及极端灾害性天气的频繁爆发，使黄河下游面临更加严峻的洪灾风险。黄河开封河段是黄河下游“地上悬河”最严重的河段；河道宽、浅、散、乱，淤积速率高，主流游荡变化剧烈，易发生决溢灾害，俗称“豆腐腰”。开封河段是历史上黄河下游河道最易决溢改道的河段，也是未来50年内黄河下游决溢改道潜在危险的重点河段之一。黄河开封段一旦决口，开封城将面临灭顶之灾。项目以开封作为研究区域，从地理位置因素、气象水文因素和防洪排涝工程措施三个方面进行致灾因子的辨识和变化研究；从气候变化因素和下垫面因素两个方面进行孕灾环境演化趋势分析；从城市不同土地利用类型的耐淹特征和快速城镇化过程中土地利用类型的变化进行承灾体类型和演化趋势分析。根据对开封黄河段多次实地考察和文献资料的收集整理校核，分析得到开封黄河段极易发生决溢的地点在柳园口险工、王庵控导工程和东坝头险工三处地点。在假设黄河发生百年一遇洪水事件条件下，运用情景分析技术和MIKE11模型中的溃堤分析模块对开封黄河段极易发生决溢洪水的柳园口险工、王庵控导工程、东坝头险工3个河段进行洪水决溢情景模拟分析，得到洪水在不同决溢地点发生的淹没状况；运用MIKE21模型与3S技术结合对洪水在开封地区演进的动态过程进行模拟，得到洪水在开封不同区域不同时相的淹没深度和淹没范围，并建立开封市洪水淹没风险动态数据库；根据开封市不同土地利用类型对水动力学模型中的糙率系数进行准确率定；同时建立不同土地利用类型的洪灾损失率函数，并通过市场调查问卷得到不同土地利用类型单位面积的成本估值；根据开封市洪水淹没风险动态过程模拟结果、不同土地利用类型洪灾损失率函数及其单位面积的成本估算，对黄河百年一遇洪水事件条件下开封决溢洪水可能造成的直接经济损失进行洪灾损失评估，并建立开封市洪灾损失数据库。根据开封市洪灾风险等级划分标准和区划原则，编制开封市洪灾风险区划图；依据开封市洪灾风险区划图，重点对洪灾高风险区域提出有针对性的防洪工程建议和应急管理减灾对策。这不仅可以丰富城市洪灾过程与风险评估基本理论，而且还为开封市及其它沿黄城市制定城市发展规划和防洪减灾应急管理提供科学依据。