黄土丘陵沟壑区流域泥沙连通性对降雨与人类活动的响应机制

Aiming at the problems of variation and attribution of soil erosion on the Loess Plateau and sediment discharge in the Yellow River under large-scale ecological restoration in the Loess Plateau region, the project will be executed in a typical small watershed in the loess hill and gully region. Based on the theories and methods in disciplines of soil erosion, landscape ecology, hydrology and geomorphology, combining with the conceptual framework of sediment connectivity, the man-made and natural sediment source and sink units and their spatial distribution pattern in the watershed will be identified and analyzed. The characteristics of erosion sediment yield of typical sources, sediment accumulation or interception of typical sinks, and pathways of sediment transport will be surveyed and monitored under different rainfall events. Then, the main processes and degree of soil erosion under different scales with different configurations of source and sink will be analyzed. The thresholds of rainfall and the features of linkages and blockages of switch on/off of different sediment transport pathways will be investigated. The sediment connectivity of different scales and their coupling relationship with rainfall and the configuration of source and sink will be clarified. The response mechanism of erosion sediment yield and sediment connectivity to rainfall and human activities will be revealed. The main reasons for the changes of sediment into river will be expounded. By identifying the hotspots of erosion sediment, sediment deposition and sediment transport pathways in the watershed, the proper measures and layout of reducing erosion sediment sources and sediment connectivity will be proposed. This study has important theoretical significance in the developing and improving the scale effect theory of watershed erosion and sediment yield, and will provide meticulous management basis for the sustainable and healthy development of watershed.

针对黄土高原大规模生态恢复下土壤侵蚀与河流泥沙的变化及其归因问题，以黄土丘陵沟壑区典型小流域为研究对象，采用土壤侵蚀、景观生态、水文、地貌等学科的理论与方法，结合泥沙连通性的概念框架，在对人为与自然的泥沙源与汇单元及其空间分布进行识别与分析，以及对不同降雨事件下代表性源的侵蚀产沙、汇的泥沙拦截与淤积、泥沙输移路径特征进行调查与观测的基础上，分析不同尺度源汇配置下的侵蚀产沙过程与程度，研究不同类型泥沙输移路径开启与关闭的降雨阈值及阻通特征，探讨不同尺度泥沙连通性及其与源汇配置和降雨的耦合关系，揭示流域侵蚀产沙及泥沙连通性对降雨与人为活动的响应机制，阐明入河泥沙变化的主要归因，并在探明流域侵蚀产沙、泥沙淤积与泥沙输移连通路径热点区的基础上，提出减少泥沙源与降低泥沙连通性的合理措施与布局，对发展与完善流域侵蚀产沙的尺度效应理论具有重要意义，可为流域可持续健康发展提供精细化管理依据。

针对黄土丘陵沟壑区大规模生态恢复下土壤侵蚀与河流泥沙变化及其归因问题，采用土壤侵蚀、景观生态、水文、地貌等学科的理论与方法，结合泥沙连通性的概念框架，开展了小流域泥沙连通性对降雨与人类活动的响应机制研究。以安塞坊塌小流域为研究对象，采用无人机航拍获取高精度影像和DEM，分析了小流域及其5个典型坡沟的泥沙源汇及输移路径的分布特征；依据11个径流小区观测、35个滑坡面细沟侵蚀量测及典型滑坡面与道路侵蚀动态监测，研究了不同坡面、滑坡面、道路等泥沙源的侵蚀特征及其对降雨的响应；基于淤地坝淤积层的调查与识别，明确了坝地泥沙汇的拦截淤积特征及其对降雨的响应；基于沟缘线切沟的动态监测，探究了退耕坡面植被恢复对沟谷侵蚀产沙的影响；依据流域降雨径流泥沙监测数据，研究了坡沟、支沟与小流域尺度源汇配置下的侵蚀产沙程度；通过场次降雨事件的追踪调查，探明了坡沟与流域主沟道泥沙输移路径及其阻通开关对降雨的响应特征；在对坡面、坡沟和小流域尺度潜在泥沙连通性分析的基础上，研究了支沟横向泥沙连通性与主沟道纵向连通性及其对不同降雨事件的响应，明确了不同空间尺度泥沙连通性与降雨和源汇配置的关系，构建了泥沙连通性指数，分析了放牧、农作及淤地坝等人为活动对泥沙连通性的影响。进而结合子洲“7·26”特大暴雨土壤侵蚀调查，研究了坡沟、沟道与小流域尺度侵蚀产沙与泥沙连通性对特大暴雨的响应特征；并依据子洲岔巴沟和延河流域24个典型淤地坝泥沙淤积、4个典型小流域淤地坝类型及其与下游沟道连通方式的调查，研究了淤地坝拦沙作用对流域生态修复模式与降雨的响应，阐明了淤地坝和下游沟道的泥沙连通程度以及对流域泥沙连通性的影响机理。本研究从坡面、坡沟、沟道和小流域尺度，揭示了泥沙连通性对降雨与人类活动的响应机制，对发展与完善流域侵蚀产沙的尺度效应理论具有重要的理论意义，可为流域可持续健康发展提供精细化管理依据。