山丘区小流域精细化水文建模及不确定性研究

Flooding in small-scale watershed in mountainous area is characterized by the short time periods and the rapid rise and recession due to the complex underlying surfaces, various climate type and strong effect of human activities. It is hard for present hydrological models to describe the variation of flooding in both time and space accurately. Therefore, there are still significant randomness and uncertainty in the flood foresting. Based on the refined hydrological mechanism, a distributed hydrological model is proposed and the uncertainty is also quantified. According to the analysis of hillside landscape attributes, a method is raised to divide the mechanism of runoff yield and excess infiltration. Based on mathematical physical equations, the effect of flow concentration in river channel and gridding is studied. A distributed hydrological model based on the compound runoff and variable velocity field is established. Meanwhile, the effect of precipitation data, DEM resolution, land utilization resolution and their interference on the uncertainty of flooding is illustrated. The research achievement is expected to expend the present flood forecasting theory, improve the disaster defense ability against flash flooding and provide significant value for both academic research and engineering application.

山丘区小流域下垫面条件复杂，气候类型多样，加之受人类活动的强烈影响，流域暴雨洪水历时短、陡涨陡落，现有水文模型还不足以准确描述洪水时空变化过程，导致洪水预报存在较大的随机性和不确定性。为此，以复杂下垫面条件下产汇流过程精细化描述为突破点，提出能够反映山丘区洪水时空变化过程的分布式水文模型并定量分析模型各类建模数据的不确定性影响。研究关键山坡地貌属性对蓄满、超渗产流机制的影响规律，提出山丘区产流机制的划分方法；探究流经水量对河道与坡面网格汇流过程的影响，采用严格的数学物理方程描述各网格的地表汇流过程；建立基于空间混合产流机制和变化流速场的分布式水文模型；在此基础上，分析不同降雨来源、DEM分辨率和土地利用精度对山洪预报结果的影响，阐明各建模数据及其相互耦合作用对山洪预报不确定性的影响规律。研究成果将发展现有山丘区暴雨洪水预报基础理论，进一步提升山洪灾害防御能力，具有重要的学术意义和工程价值。

山丘区小流域非线性程度高，下垫面类型复杂多样，缺少可靠的长系列降雨洪观测资料，导致山丘区暴雨洪水预警预报存在较大的随机性和不确定性。本项目在全国范围内选取具有代表性的流域，实现了小流域产流机制的空间精确划分，重点研究模型内部产流结构的合理性和不确定性问题，提升模拟精度。推求单位线峰值经验公式，并采用可变模糊聚类方法对小流域单位线进行分类，建立小流域特征因子与单位线峰值之间的经验公式。针对缺乏综合考虑多种数据来源的不确定性，提出山丘区水文预报模型与数据精度匹配方法。归纳总结不同原理、不同产汇流机制的水文模型应用特点及适用条件，基于ANOVA方差分解研究水文模拟不确定性。在此基础上，分析降雨对山丘区小流域径流模拟不确定性的影响。本项目突破单一模型水文模拟的局限性，提出适用于山丘区小流域的水文模型选择方法，建立水文模拟不确定性来源量化框架，挖掘不同类型数据与水文模型的匹配关系，项目研究成果可直接应用于山洪灾害预报预警工作，为全国山洪灾害防治工作提供重要的技术支持，具有较大工程应用和科技支撑价值。