粉质土斜坡降雨侵蚀产沙过程及其动力学机制

    PROCESS OF RAINFALL EROSION AND SEDIMENT VIELD ON SILTY SLOPE AND ITS DYNAMIC MECHANISM

    • 摘要: 我国黄土高原地区正面临着生态环境严重退化、边坡浅表灾害频发等一系列生态环境问题及地质灾害问题,研究探讨黄土高原粉质土斜坡降雨侵蚀过程及动力学机制对当地水土保持工作的开展具有重要意义。本文通过现场选取典型试验坡面,开展野外模拟降雨试验,研究了不同降雨强度(60h-1、90h-1、120h-1)、坡度(30°、34°、38°)及植被覆盖度(30%、60%)下坡面侵蚀过程、形态及动力学特征。主要取得以下成果:(1)不同试验条件下坡面产流时间存在差异,产流时间在56~100s之间;坡面入渗、产流及产沙量随降雨强度、坡度和植被覆盖度变化明显;坡面的产流率呈幂函数变化规律,各坡面的产沙率均表现出先快速增大后缓慢降低的变化特征。(2)降雨过后坡面细沟形态参数变化明显,结合DEM数据显示,坡面细沟均表现出上部窄而浅,下部宽而深的特点;综合来看,90h-1雨强下细沟发育程度最高。(3)坡面细沟水流平均流速随降雨强度和坡度的增大而增大,随植被盖度增加而减小,根据计算水力学参数可得坡面水流特点表现为“紊状缓流”。(4)坡面平均产沙率与平均径流剪切力、平均径流功率和单位径流功率之间存在显著的线性相关性,单位径流功率更适合用来描述研究区坡面产沙过程。

       

      Abstract: The Loess Plateau of China is facing a series of ecological environment problems and geological disasters,such as serious degradation of ecological environment and frequent superficial disasters on slopes. It is of great significance to study the rainfall erosion process and dynamic mechanism of silty soil slope in the Loess Plateau for local soil and water conservation work. In this paper,the erosion process,morphology and dynamic characteristics of slope erosion process under different rainfall intensity(60h-1,90h-1,120h-1),slope(30°,34°,38°) and vegetation coverage(30%,60%)were studied by field simulated rainfall experiments on typical experimental slopes. The main research results are as follows: (1)The initial runoff time of slope under different experimental conditions is between 56s and 100s; slope infiltration,runoff and sediment yield change obviously with rainfall intensity,slope and vegetation coverage; the runoff yield is a power function,and the sediment yield shows the characteristics of rapid increase at first and then slow decrease. (2)After rainfall,the morphological parameters of rills change obviously. Combined with the DEM data,the rills on the slope show the characteristics of narrow and shallow in the upper part but wide and deep in the lower part. In general,the rill development degree is the highest under 90h-1 rainfall intensity. (3)The average velocity of rill flow on the slope increases with the increase of rainfall intensity and slope,and decreases with the increase of vegetation coverage. According to the calculated hydraulic parameters,the characteristics of slope flow are "turbulent slow flow". (4)There is a significant linear correlation between the average sediment yield rate and the average runoff shear force,the average runoff power and the unit runoff power,and the unit runoff power is more suitable to describe the process of sediment yield in the study area.

       

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