太行山东部石质山区生态建设对暴雨洪水过程的影响机理

Vegetation changes can influence the storm flood process by affecting the hydrological process of interception, infiltration, soil flow, and hydrological and physical parameters such as surface roughness, soil moisture content. A large-scale ecological construction has strengthened the impact of vegetation on the flood process and can, to a certain extent, enhance the ability of the green infrastructure in the slope system to regulate flooding. However, the current relevant research focuses on the changing trends in flood elements or the impact of the change in the area of surface cover and conversion between different land use types on flood runoff. The mechanism study of the change in the key elements of flood formation is still weak, especially for the characteristics of rainstorm-runoff reflecting the underlying surface of soil and vegetation in the rocky mountainous area of Taihang. In this project, we intend to adopt a combination of field prototype observations, indoor control experiments and model simulation analysis, in order to analyze the mechanism of the impact of changes in the underlying surface on the key elements of flood formation from the point of view of eco-hydrology mechanism, and then evaluate the ability of continuous vegetation restoration for regulating storm floods in the eastern rocky mountainous areas of Taihang for more than 30 years. This project has important scientific and practical value for systematically understanding the basic features and mechanisms of eco-hydrological processes in rocky mountain areas, further enriching the theory of restoring ecological hydrology, and supporting the practice of ecological restoration in the Taihang Mountains.

植被变化通过改变截留、入渗、壤中流等水文过程及地表糙度、土壤含水量等水文物理参数，进而影响暴雨洪水过程。大范围的生态建设强化了植被对洪水过程的影响，并且可在一定程度上提升坡面系统植被绿色基础设施对洪水的调节能力。当前有关研究重点关注洪水要素的变化趋势或地表覆被的面积变化及不同土地利用类型之间的转化对洪水径流的影响，而对洪水形成的关键要素过程变化的机理研究仍显薄弱，尤其是针对太行山石质山区下垫面土壤植被特征开展的暴雨产流特性研究较少。本项目拟通过野外原型观测、室内控制实验、模型模拟分析相结合的方法，从生态水文作用机制角度深入剖析下垫面变化对洪水形成的关键要素过程的影响机理，并评价太行山东部石质山区30余年来持续开展的植被恢复对暴雨洪水调节能力。本项目对于系统地认知石质山区生态水文过程的基本特征和机理，进一步丰富恢复生态水文学理论，支撑太行山区生态恢复实践工作，具有重要的科学意义和实践价值。

作为重要的“绿色基础设施”，山区生态建设和植被恢复对于充分发挥流域坡面系统对暴雨产流过程的综合调节能力，有效应对水循环过程的“极值化”态势具有重要作用。.本研究围绕生态建设对洪水形成的关键要素过程影响，结合野外调研，分析了太行山石质山区地表覆被变化及暴雨洪水演变特征；在此基础上从水循环过程角度识别下垫面变化对洪水关键要素过程的影响机理；构建研究区水文模型，定量评价生态建设对洪水调节能力，系统分析流域植被恢复对洪水的影响机制。.主要研究成果如下：（1）流域近30年间土地利用总体格局没有发生大的变化，但林草地生态系统稳定性增强，水土保持措施多样、成效显著。（2）紫荆关流域暴雨洪水频次有减少的趋势，年最大洪峰在1998年前后发生减少突变。2000年之后大部分洪水量级在2年一遇以下。流域年最大洪峰流量和次洪径流深均呈现显著的减少趋势，场次洪水的历时有微弱的增加趋势。生态建设活动起到了削减洪峰流量，延长洪峰滞时的作用，并在一定程度上改变了洪水过程形态。（3）对于5年一遇以下洪水，洪峰和洪量的平均减少幅度分别为8.0%和13.7%；5年一遇以上洪水，洪峰和洪量的平均减少幅度分别为5.6%和9.1%。流域平均蓄水容量和稳定下渗率均有明显的增加，其中稳定下渗率增大了60%。.本研究从生态水文作用机制角度系统剖析生态建设影响洪水要素的作用过程，基于垂向混合产流机制构建了紫荆关流域雨洪模型，从产流机制上印证了流域生态建设的成效，进一步丰富了植被调洪作用的基本认识。土石山区的自然本底状况决定不可能大规模改变生态系统格局，生态建设应以增强生态系统的稳定性和韧性为主，实现自然生态系统的良性演替。研究成果对于支撑太行山区生态恢复实践工作，具有重要的科学意义。