大清河水系山区下垫面变化对洪水过程影响机理及模拟分析

In this research, a sub-basin of Haihe river basin-Daqinghe river basin is selected. Several typical watersheds will be selected in the Daqinghe river basin, and then field investigation are carried out to collect rainfall-runoff data. Trend analysis of flood characteristics, including flood peak and volume, and the control factors(rainfall characteristics, all underlying factors) will be done. According to the hydrometeorologic and underlying surface data, hydrological response unit will be classified by ArcGIS. Then rainfall runoff experiment will be carried out in each hydrological response unit to identify the main runoff generation components and runoff generation mechanism. Based on the rainfall runoff experiment, a distributed hydrological model will be established in each hydrological response unit. The model will be calibrated and verified using historical rainfall-runoff data and underlying surface data. Flood processes are simulated by using the established hydrological model under different historical underlying surface conditions. In the simulation, small hydraulic engineerings will be considered. Floods of different return periods which are less than check flood standard and greater than check flood standard are simulated. The storage and operation mode are considered when simulating floods less than check flood standard. When simulating floods greater than check flood standard, it is assumed that the dam will break. The dam-break flood processes should be calculated. Through the flood simulation in different conditions, the effects of each underlying surface on floods of different frequencies could be quantified, and the effects of each underlying surface on runoff generation processes can be identified. The results of this study can provide theoretical method for design flood re-check, and also provide scientific basis for hydraulic engineering operation in the Daqinghe river basin.

项目以海河流域的大清河水系为研究背景，在充分现场调研和收集历史资料的基础上，在大清河水系选择代表流域，对洪水特征及其影响因子（降水特征、各类下垫面要素）进行变化规律分析。根据代表流域的水文气象及下垫面资料，利用ArcGIS进行流域水文单元划分，通过野外降雨径流观测，研究各类水文单元的主要产流模式和产流机制，从而构建以水文单元为基本计算单元的分布式水文模型，并对模型进行参数率定和验证。利用建立的分布式水文模型对实测暴雨洪水进行不同下垫面条件下的模拟，综合考虑流域内小型水利工程在遭遇低于校核标准洪水时的拦蓄作用，以及遭遇超标准洪水时的溃坝形式及溃坝洪水过程，定量分析各类下垫面要素变化对不同量级洪水的影响程度，辨识各类下垫面要素变化对产汇流过程的影响规律。研究成果可为大清河水系下垫面变化条件下的设计洪水复核提供理论基础，同时也可为大清河水系水利工程的合理运用提供科学依据。

由于人类活动的影响，流域下垫面发生了较大的变化，对流域的水文过程尤其是洪水过程产生了一定的影响。本研究以大清河流域为研究对象，在大量收集水文气象、下垫面等资料的基础上，选择典型子流域分析实测暴雨洪水特征序列的变化特性，包括趋势、变异等分析。并利用遥感资料分析了流域土地利用的变化程度，认为洪水特性的变化主要是由下垫面变化导致。为了研究下垫面变化对洪水特性的影响程度，首先运用降雨径流相关关系和相似暴雨洪水对比等统计方法进行了研究，结果表明，草地和耕地面积比例的增加导致次洪量模数和洪峰模数增加，林地面积比例的增加会导致次洪量模数和洪峰模数的减小。在分析各类下垫面对产汇流影响机理的基础上，建立了考虑下垫面变化的水文模型，利用历史实测暴雨洪水资料对模型进行了验证，说明模型具有一定的精度。在此基础上，对多场洪水进行了不同下垫面条件下的模拟，给出了下垫面变化对洪水的影响程度。由于不同流域下垫面变化特征差异，各类下垫面变化引起的洪水变化程度也不相同。以阜平子流域为例，大于10年一遇的洪水洪量减少10%~20%，洪峰减少6.1%~11.0%，5~10年一遇洪水洪量减少20%~25%，洪峰减少41.1%~42%，小于5年一遇洪水洪量减少25%~30%，洪峰减少41.6%~52.2%。该研究可为大清河流域设计洪水修正及防洪决策提供指导，并可推广应用于其他流域。