城市群圩垸式防洪的流域洪水响应与风险评价研究

With the accelerated process of urbanization, urban flood control is developing from flood control of singer urban to that of urban agglomeration. Among flood controls of urban agglomeration, single urban playing its own role to construct urban flood control circle, which known as polder type flood control model, is the extensively used model at present. However, what influence will be induced on basin flood situation and urban flood risk while this model is adapted? How to coordinate the relation between urban and river basin flood control? These two questions are the first problems that need to be solved. This study takes Qinhuai River basin located in Yangtze delta area as research object, in which flood control polder of six cities, such as Nanjing and so on, are included. And obviously it is typical. Methods like remote sensing, GIS technology, digital geography and so on are employed to analyze the variation of basin pregnant disaster environment. And HEC-HMS hydrological model and HEC-RAS hydraulic model are established for simulating basin flood process under polder type flood control model. Besides, Multi-dimensional probabilistic risk assessment is introduced to analyze flood risk. The analysis results will reveal the mechanism and impact of polder type control model on basin pregnant disaster environment, as well as the variation of flood risk of urban agglomeration that may be brought about. Then the reasonable scale and layout can be determined. Finally, the analysis and assessment method for urban agglomeration flood and disaster based on polder type flood control can be obtained. The achievements, which are rarely reported in China, are of great value in application and popularization, and they will extend the connotation of urban flood control and hydrology.

随着城市化进程加快，城市防洪正由单座城市防洪向城市群防洪发展。在城市群防洪中，目前普遍采用单座城市各自为阵构建城市防洪圈的圩垸式防洪模式。该模式对流域洪水情势和城市洪灾风险将产生怎样的影响？如何协调城市与流域防洪的关系？这是迫切需要回答的问题。本项目以长三角地区秦淮河流域为研究区，该流域内现有包括南京等六个城市防洪圩垸，极具典型性。拟采用遥感、GIS技术和数字地理等方法解析流域孕灾环境的变化；构建流域HEC-HMS水文模型和HEC-RAS水力学模型模拟圩垸式防洪模式下流域洪水过程；采用多维概率风险评价等方法分析洪灾风险。揭示圩垸式防洪模式对流域孕灾环境、洪水情势的影响及其机制；揭示其对城市群洪灾风险可能带来的变化；探讨城市防洪圩垸的合理规模与布局；建立基于圩垸式防洪模式的城市群洪水、洪灾分析与评价方法。研究成果有较好应用推广价值，将拓展城市防洪和城市水文学的内涵，而目前我国鲜有相关报道。

本研究在分析秦淮河流域下垫面格局变化以及水系格局变化特征的基础上，建立HEC-HMS和HEC-RAS模型，研究圩垸式防洪模式与流域洪水之间的响应关系，揭示流域孕灾环境与洪灾风险的新特点。发表相关文章9篇（标注论文9篇），协助培养博士1名，独立培养硕士6名，参加国际学术会议5人次，申请发明专利1项，获得教育部科技进步二等奖1项，安徽省水利优秀成果二等奖1项，完成了项目的预期成果指标。主要的研究成果概括如下：.1、伴随着城市化进程的进行，土地利用变化有以下特征：前期有农田、林地向旱地转化，以及少量旱地、农田向建设用地转化；后期主要是农田、林地、旱地等土地利用类型直接转化为建设用地。水系格局变化有以下特征：（1）流域内河流长度减小，河网密度下降；（2）水系结构稳定性变差；（3）河网结构不断简化，细支河道消失；（4）水域总面积减小，而面状水体在局部地区有增加。.2、秦淮河流域农村圩垸式防洪模式较无圩垸防洪模式，削减了圩外河道洪水的洪量及洪峰；而城市群圩垸式防洪模式增大了圩外河道洪水的洪量及洪峰。洪水规模越小，圩垸对洪量的影响越显著。圩垸分布在流域出口对洪水的洪峰及洪水过程的流量削减程度低于流域中上游圩垸的作用效果。对于不同规模洪水，随着流域城市化水平逐渐提高，流域洪量、洪峰相较于当前城市化水平均逐渐增大。.3、秦淮河流域城市群圩垸式防洪模式较无圩垸防洪模式，增大了圩外河道洪水的水位。洪水规模不同对流域洪水水位影响程度不同。城市圈圩垸分布越靠近流域出口对水位的影响程度越弱，越靠近上游影响越显著。对于不同规模的洪水，随着流域城市化水平逐渐提高，流域水位相较于当前城市化水平均逐渐增大。.4、对某一量级的洪量，秦淮河流域有城市圩垸工况下发生超过该量级洪量的洪水的概率大于无圩垸工况下。洪水位、洪峰的超过概率亦如此。在洪量相同的情况下，有圩垸的工况比无圩垸工况计算的洪灾风险更大，有圩垸工况的防洪标准设计值也相应增大。