坡耕地降雨径流与土壤侵蚀特征研究

Study on Rainfall Runoff and Soil Erosion Characteristics of Sloping Farmland

研究人工模拟降雨对坡耕地土壤侵蚀特征的影响,旨为北方土石山区坡改梯建设提供科学依据。以北方土石山区典型砂质壤土为研究对象,采用人工模拟降雨试验的方法,在室内模拟不同坡度(10°、15°、20°和25°)、不同降雨强度(40、90、120和180 mm/h)下的坡面产流和产沙过程,研究不同坡度和降雨强度对坡面土壤侵蚀过程的调控机制。结果表明:(1)坡面开始产流所需的时间不受坡度的影响,随着降雨强度的增大,坡面产流所需的时间明显缩短;(2)在降雨强度一定的条件下,随着坡度的增大,坡面产沙量逐渐增加,本试验坡面最高产沙量的临界坡度约为22°;(3)产流量随坡度变化并非单调的递增或递减趋势,而是随着坡面由缓变陡呈先增加后降低的变化;(4)在降雨量相等的前提下,大降雨强度能够带来较大的单位时间产流量,但并不能保证总产流量也最大;在其他条件一致时,坡面侵蚀随着降雨强度的增大而增加。在降雨强度一定的条件下,坡面产沙量存在临界坡度,不同土质、不同降雨强度下的临界坡度尚需进一步研究。

The study on the effects of simulated rainfall on soil erosion characteristics of sloping farmland could provide a scientific basis for the construction of slope to ladder in the earth rock mountainous area of North China.Taking the typical sandy loam in the earth rock mountain area of North China as the research object,using the method of artificial rainfall simulation test,the slope runoff and sediment generation processes under different slopes(10,15,20 and 25°)and different rainfall intensities(40,90,120 and 180 mm/h)were simulated indoors,and the regulation mechanism of different slopes and rainfall intensities on the slope soil erosion process was studied.The results showed that the time required for runoff production on the slope was not affected by the slope,and the time required for runoff generation on the slope was significantly shortened with the increase of rainfall intensity.Under the condition of constant rainfall intensity,the slope sediment amount increased gradually with the increase of slope.The critical slope of maxium sediment amount in this experiment was about 22°.The runoff did not have the trend of increasing or decreasing monotonically with the slope change,but it increased first and then decreased with the slope from slow to steep.On the premise of equal rainfall,high rain intensity could bring large runoff unit time,but it could not guarantee the maximum total runoff.When other conditions were the same,slope erosion increased with the increase of rain intensity.Under the condition of certain rainfall intensity,there was a critical slope for slope sediment amout.The critical slope under different soil properties and different rainfall intensity needed to be further studied.