含砾石红壤坡面水文过程和产流产沙特征研究

Gravel soil is an important soil resource. Although gravel soil is widely distributed in our country, the research of the soil containing gravel on physical properties, hydrological processes, especially erosion process is scarce. Gravel can not only change the composition and structure of the soil, but can affect soil physical properties and mechanical properties of water as well, such as, soil bulk density, porosity, infiltration. The soil erosion of hilly red soil region in South China is second only to the loess plateau region, but studies for the gravel red soil in the mechanism of slope runoff and sediment have rarely been reported. This project aiming at the features that slope surface erosion process is influenced by the factors of gravel cover, the degree of slope, and slope length, adopts the means of field survey observation, digital image processing technology, and artificial simulation rainfall test, carrying out the survey of distribution law and space distribution pattern of gravel red soils. It has analyzed the effect law of gravel factor on soil water into infiltration and evaporation and proved gravel space distribution features on red soil physical properties, and slope runoff and sediment of effect mechanism. The result of the research can provide scientific basis for accurate prediction of gravel soil erosion and promotion of gravelly soil slope surface water conversion; meanwhile it can improve the research and development of transformation of soil moisture on slope model, simulation of hydrological processes and soil erosion models.

含砾石土壤是一种重要的土壤资源，尽管我国含砾石土壤分布广泛，但有关含砾石土壤物理性质、水文过程特别是侵蚀过程的研究却很少。砾石的存在不仅会改变土壤的物质组成和结构，还会影响土壤容重、孔隙度及土壤入渗等土壤物理特性和水力学特性。我国南方红壤丘陵区是仅次于黄土高原的严重水土流失区域，但目前对于该区砾石在坡面产流产沙中的作用机制研究还鲜有报道。本项目针对坡面侵蚀过程受砾石覆盖、坡度、坡长等因素影响的特点，运用野外调查与观测、数码图像处理技术、人工模拟降雨试验等方法手段，开展红壤坡面砾石的分布规律与空间分布格局的调查、观测，分析砾石因子对土壤水分入渗、蒸发的影响规律，探明砾石空间分布特征对坡面土壤物理性质、产流产沙过程的影响机制，研究结果可为准确预报含砾石土壤的侵蚀情况提供科学依据，并促进砾石土壤坡面水分转化、流域水文过程模型模拟和土壤侵蚀模型的研究与发展。

含砾石土壤是一种重要的土壤资源，砾石的存在会对土壤物理性质等产生影响。然而，不同砾石含量、覆盖度、大小及其在土壤中的位置会对红壤坡面降水分配、径流形成产生怎样的影响？覆盖砾石和嵌套砾石坡面径流过程及土壤侵蚀过程有何差异？基于以上科学问题，本研究以浙江省红壤丘陵区典型含砾石土壤坡面为研究对象，针对坡面侵蚀过程受砾石存在、降雨强度和坡度等因素影响的特点，运用野外调查和室内人工模拟降雨试验相结合的方法，开展红壤坡面不同砾石存在形式与土壤水文物理性质的关系研究，及红壤坡面砾石对降水分配规律、坡面径流形成的作用研究。从而探讨砾石存在对土壤水分入渗和蒸发的影响机理，阐明砾石对坡面水文过程和产流产沙的影响机制，为非均质土壤坡面水土过程、坡面水文和土壤侵蚀模型模拟研究提供科学依据。取得的主要进展有：1）砾石存在对坡面产流过程有着深刻的影响，雨强相同和坡度相同时，初始产流时间T含砾石>T无砾石。降雨强度较小时砾石存在（嵌套或覆盖）对坡面径流量削减的效果更显著，随着降雨强度的增大，降雨强度对坡面产流的影响程度强于坡度和砾石的影响。2) 覆盖砾石和嵌套砾石坡面60mm/h雨强时的入渗率高于120mm/h雨强，平均入渗率都随坡度增加呈下降趋势，雨强60mm/h时入渗率为嵌套砾石>覆盖砾石>无砾石；坡度相同时，嵌套和覆盖砾石的坡面产流率较无砾石坡面明显减少，但雨强增大后，砾石对坡面产流率减小的影响被掩盖。3）嵌套砾石0%、10%、20%、30%各红壤坡面壤中流产流过程基本都呈单峰型，且趋势一致。地表径流所占比例均随雨强的增大而提高，雨强120mm/h时地表径流所占比例为76.1%~93.5%；壤中流所占比例随雨强增大而减小，雨强60mm/h时壤中流所占比例为7.3%~30.0%。降雨强度是影响壤中流过程的主要因素，砾石含量则是次要因素。增加降雨强度会阻碍坡面壤中流的发生；而砾石含量增加会有助于较缓坡面壤中流的发生，而阻碍较陡坡面壤中流的形成。