黄土丘陵区切沟发育过程与形态模拟

Gully erosion is the most important water erosion pattern in the loess hilly area. Gully development not only causes severe land degradation and soil productivity loss, but also threatens the river operation security and destroys the humanity environment. Therefore, research on gully developing process and its geomorphology simulation will enhance deep understanding of soil erosion mechanisms and provide important basis for controlling soil erosion and reducing river sediment yield. However, there is very weakness on studying gully erosion development process due to complexity of gully erosion process and limitation of research technology, which influences developing erosion prediction at complex landforms and arrangement of suitable soil and water conservation measures. Each 5 typical sites in two sub-regions (No. 1 and No. 2) in Hilly Loess Region, where are heavy erosion areas, especially severe gully erosion, are taken as the research sites. The combined methods of field survey, measurements of high precision GPS, Lidar technique monitoring and rainfall simulated experiment are used to obtain the valuable observed information of gully erosion development. Moreover, it is conducted to quantify the dynamic gully erosion processes, and to analysis the process and mechanism of confluence and sediment process in gully catchments area. As well as, a morphogenesis model, which can represent the gully develop process, is established by using a large erosion dataset obtained from Lidar and high precision GPS techniques. The research results will provide theoretical basis for developing process-based water erosion model at complex landforms and also provide important basis for controlling soil erosion and reducing river sediment yield.

切沟侵蚀是黄土丘陵沟壑区最重要的侵蚀方式，其发生发展不仅破坏土地资源，加剧洪涝危害和威胁人居环境，且对当地和异地的粮食和生态安全造成严重威胁。因此，开展切沟侵蚀发育过程及其形态模拟研究，不但深化对土壤侵蚀规律的认识，而且为侵蚀防治提供重要的科学依据。但由于切沟侵蚀发育过程的复杂性及影响因素的多变性，以及其发生发展的随机性、偶发性和非线型性，使切沟侵蚀过程动态监测研究具有很大难度，从而导致切沟侵蚀过程研究非常薄弱。本研究在切沟侵蚀严重区的黄土丘陵沟壑区第一副区和第二副区各选5个典型样区，采用野外定位观测、高精度GPS和三维激光扫描技术以及模拟试验技术，获取切沟侵蚀发育过程的第一手观测资料，定量刻画切沟侵蚀动态发育过程，分析切沟集水区汇流和输沙过程与机理，建立切沟发育的形态模拟模型，研究成果不仅为针对性的布设水保措施提供重要的科学依据，也为复杂地形区侵蚀预报模型建立提供理论支持。

开展切沟侵蚀发育过程及其形态模拟研究不仅可以深化对土壤侵蚀规律的认识，为侵蚀预报模型的建立提供理论基础，也可为侵蚀防治提供科学依据。但由于切沟侵蚀发育过程的复杂性、影响因素的多变性和非线型性等，切沟侵蚀过程动态监测研究具有很大的难度，导致切沟发育过程及其形态模型研究非常薄弱。本项目以黄土丘陵区切沟侵蚀为研究对象，选取切沟侵蚀典型样区5个和典型切沟样点70余个，利用三维激光扫描技术动态监测了切沟形态特征及其发育过程；基于野外定位观测、模拟试验和立体摄影测量技术等，量化了沟蚀发育过程；运用模型模拟手段，分析了降雨过程中侵蚀沟集水区汇流过程及其水流动力学参数的空间变化；基于数据集成与GIS平台，建立切沟发育的形态模拟模型。.项目执行4年来，圆满完成了项目研究任务和考核指标。1）发表论文21 篇，其中SCI 和EI 收录论文13篇，出版编著1部，参编英文编著2部；2）培养研究生研究生10 名（博士7 名，硕士3 名）；3）对研究成果进行了广泛的学术交流，参加国际会议9人次，举办了海峡两岸学术研讨会1次，深入开展了中美实质性的合作研究；4）研究成果引起国内外高度关注，获批中奥合作项目（Assessment of gully erosion in the Chinese Loess Plateau ）1项；5）部分研究成果已被写入《Encyclopedia of Soil Science》中的“Gully erosion”条目。. 项目的主要研究进展表现在6个方面：1）建立了基于立体摄影测量技术动态监测侵蚀沟形态与水流参数的方法，提出了划分发育活跃期侵蚀沟沟头和沟壁的方法；2）分析了发育活跃期切沟形态特征，构建了基于切沟长度和表面积估算切沟体积的模型；3）建立了0.1m与5m分辨率DEM提取切沟形态参数间的转换模型；4) 量化了地形参数和降雨对侵蚀沟集水区土壤侵蚀的影响；5）基于CCHE2D模型模拟了侵蚀沟集水区汇流过程及其水流动力学参数特征；6）分离了沟头溯源侵蚀、沟壁扩张和沟底下切三种侵蚀方式对沟蚀的贡献，建立了沟壁扩张侵蚀过程方程。