地表凸起与凹陷对产汇流及侵蚀的不同作用机制

Due to the natural physical structure characteristics of soil surface mounds and depressions, they influence runoff and soil erosion to totally different directions in the process of soil water erosion. In the present study of runoff generation, runoff concentration and soil erosion theory, soil surface mounds and depressions were never been researched respectively to evaluate their different effects on runoff. Therefore, on the basics of former research work, this study using simulated rainfall experiments on the field, combined with Geographic Information System and Digital Close-range Photogrammetry technology to explore the effects of soil surface mounds and depressions on runoff generation mechanism, flow pathway, runoff drainage network, infiltration, deposition and sediment yield under set up both individually and combined conditions. The objective of this study is to make clear the different mechanisms of runoff generation and concentration as well as erosion response rules on the function of watershed effects and runoff blockage from mounds, and water storage function and runoff delay from depressions. And to abstract the runoff concentration hydrologic network of soil mounds and depressions, build the runoff and erosion models of mounds and depressions. And find out the best soil water conservation benefits for mounds and depressions combination through adjusting and analyzing the combination spacing of soil mounds and depressions, in order to seek for new soil and water conservation treatments.

坡耕地上，地表凸起与凹陷由于自身的物理结构特征，在水蚀过程中对径流和侵蚀都产生了完全不同方向的影响。在目前的产汇流及侵蚀理论研究中，地表糙度对产汇流的影响还未曾系统地将凸起与凹陷分开进行过研究。因此，本项目在前期研究的工作基础上，通过野外模拟人工降雨试验，结合地理信息系统、近景摄影测量等技术，探求地表凸起与凹陷在单独、组合设置这两种形式下，对产流机制、汇流路径、水文网络、入渗、沉积、产沙等方面的影响。以明确在地表凸起的分水岭作用和对径流的阻碍作用，以及凹陷的蓄水作用和对径流的延缓作用下，二者不同的产汇流机制及侵蚀响应规律。并提取地表凸起与凹陷的汇流水文网络，建立二者的产汇流模型及侵蚀模型。此外，通过对地表凸起与凹陷之间组合间距的调整分析，找到具有最佳蓄水保土效益的凹凸组合，探寻新的水土保持措施。

坡耕地地表由于凸起和凹陷几何形态和物理特征的差异，导致二者对地表径流的产流、汇流过程和土壤侵蚀等方面的影响均有所不同。本项目旨在揭示凸起和凹陷在单独和组合情况下对坡面产汇流过程及土壤侵蚀的影响。研究以平坡裸地作为对照，研究了单式起伏（单凸起、单凹陷）和复式起伏（凹凸相间、凹凸相连）两种模式在3种尺度（10 cm、20 cm、30 cm）下对产汇流及土壤侵蚀的影响。结果表明：凸起会缩短产流时间、促进产流、增大产沙量、加速水土流失；凹陷则会延长产流时间、阻碍地表产流、减小产沙量、降低水土流失；二者对产汇流和侵蚀的影响均会随尺寸的增大而增加。凸起和凹陷组合以后的复式起伏对产汇流及侵蚀的影响大部分情况下介于二者之间，但连续分布的凹凸组合其产流量和径流系数却同时小于纯凸起和纯凹陷的坡面。同时，雨强和尺寸也会影响各措施的产流、产沙稳定性。单式、复式起伏的产流、产沙稳定性均随雨强的增大而降低，但随着尺寸的增大产流、产沙的稳定性也会增加。各地形措施中，单凹陷的减流、减沙效益最明显，复式起伏措施的减流、减沙效益居中，单凸起较差。连续分布的凸起也有一定的减沙效益，间隔分布的凸起则会促进产沙，凸起和凹陷组合以后的复式起伏中和了二者对泥沙的影响，减沙效益居中。汇流方面，单凸起、单凹陷、对照组和凹凸相间、凹凸相连坡面的汇流网络分别呈现出以羽毛状为主、树枝状为主、纯树枝状和以平形状为主的汇流网络特征。各措施的汇流密度与径流频度随雨强变化呈现相同的变化趋势：对照组和凸起组随着降雨强度增大其汇流密度与径流频度呈现先减小后增大的变化规律；凹陷组及凹凸组合的汇流密度与径流频度均随降雨强度增大呈现增加趋势。此外还计算分析了各地形措施的径流水动力学参数，从水动力学角度阐释了地形起伏对径流和侵蚀的影响。本研究揭示了地表凸起和凹陷在单独和组合情况下的产汇流机制与侵蚀响应，为当地水土保持和完善微地形水文模型提供了理论依据。