间歇降雨对红壤坡面土壤侵蚀特征的影响

自然条件下降雨多以间歇形式出现,而坡面土壤侵蚀又是一个渐变发育的复杂过程。通过3个雨强(60,90,120 mm/h)、5个坡度(5°,10°,15°,20°,25°)下的15场室内模拟降雨,研究一、二次降雨条件下不同雨强、坡度及降雨量对红壤坡面径流和侵蚀过程的影响,探讨间歇降雨条件下坡面侵蚀发育过程及其主要影响因素的变化。结果表明:(1)二次降雨的产流时间相比一次降雨均提前,一次降雨径流总量受到雨强、坡度和降雨量的共同影响,15°坡度是径流总量变化的一个转折点,二次降雨时降雨量的作用减弱,各雨强下的最大相差倍数减小,各坡度之间的倍数差距也减小。(2)一次降雨发生细沟侵蚀最主要的动力是降雨强度,大雨强、陡坡情况下细沟侵蚀更容易产生,而15°坡度对细沟侵蚀的产生具有重要作用,此时若发生细沟侵蚀,坡面侵蚀则多以细沟侵蚀为主,二者侵蚀量呈正比例函数关系,二次降雨的细沟侵蚀量和一次降雨过程中细沟发育情况相关,一次降雨的细沟发育越剧烈,二次降雨的细沟侵蚀量越少,此时细沟侵蚀量和总侵蚀量呈一次函数关系。总体来说,侵蚀总量的变化和细沟发育所处阶段紧密相关。(3)间歇降雨条件下,不同雨强、坡度、降雨量对坡面土壤径流和侵蚀过程的影响存在差异;同时,一次降雨土壤径流和侵蚀的变化对后期二次降雨径流和侵蚀的发展具有重要影响,使得在不同土壤侵蚀发展阶段,雨强、坡度、降雨量等因子对坡面土壤径流和侵蚀影响的程度也随之改变。

Slope Erosion and Its Changes in Red Soil Under Intermittent Rainfall

Under natural conditions, rainfall mostly occurs intermittently, and slope soil erosion is a gradual and complex process. Through 15 indoor simulated rainfall experiments, including three rain intensities (60, 90, 120 mm/h) and five slopes (5°, 10°, 15°, 20°, 25°), the runoff and erosion process were studied under the conditions of primary and secondary rainfall. The slope erosion development process and the changes of main influencing factors under intermittent rainfall conditions were discussed. The results showed that: (1) The runoff time of the second rainfall was earlier than that of the first rainfall. The total runoff of the first rainfall was affected by rain intensity, slope, and rainfall. The slope of 15° was a turning point for the change of the total runoff. The effect of rainfall was weakened during a single rainfall, the maximum difference multiple under each rainfall intensity was reduced, and the multiple gap between the slopes was also reduced. (2) The main driving force for rill erosion in a single rainfall was the rainfall intensity. Rill erosion was more likely to occur in the case of steep slopes, and the 15° slope was of great significance to the generation of rill erosion. At this time, if rill erosion occurred, the slope erosion was mostly dominated by rill erosion, and both erosion showed a positive proportional function relationship. The amount of rill erosion caused by the secondary rainfall was related to the development of the rill during the primary rainfall. The more intense the rill development of the primary rainfall, the less the amount of rill erosion caused by the secondary rainfall. The amount of rill erosion had a linear function relationship with the total erosion amount. In general, the change in the total erosion amount was closely related to the stage of rill development. (3) Under intermittent rainfall conditions, there were differences in the influences of different rainfall intensity, slope, and rainfall on the slope soil runoff. At the same time, the change of soil runoff and erosion in the primary rainfall had an important impact on the development of secondary rainfall runoff and erosion in the later period, so that at different stages of soil erosion development, the influencing extent of rain intensity, slope, rainfall and other factors on the slope soil runoff and erosion also changed accordingly.