黄土丘陵沟壑区坡面土壤侵蚀的临界坡度

Research on Critical Slope of Soil Erosion in a Hilly Loess Region on the Loess Plateau

坡度是重要的地貌因子。采用岔巴沟径流场和王家沟径流场资料,首先研究坡度与最大30min雨强(I30)对土壤侵蚀影响,然后确定了主导侵蚀为溅蚀片蚀与主导侵蚀为细沟侵蚀之间的临界雨强,最后探讨了不同侵蚀类型下的临界坡度。结果表明:1.坡度与降雨强度存在明显的交互作用,随着坡度的增大,雨强对土壤侵蚀的影响增大;2.团山沟的溅蚀片蚀与细沟之间的临界I30为0.31mm/min,同时,该临界雨强不是一定值,受下垫面因素等影响而具有一定的波动范围;3.以溅蚀片蚀为主时,土壤侵蚀存在一个<31°的临界坡度,侵蚀模数随坡度的变化趋势与径流模数随坡度变化的趋势相同,从9°～31°土壤侵蚀模数随坡度增加是先增加后减小;以细沟侵蚀为主时,在9°～31°间土壤侵蚀不存在临界坡度,土壤侵蚀模数随坡度的变化趋势与径流含沙量随坡度变化的趋势相同,从9°～31°土壤侵蚀模数随坡度增加先逐渐增加后缓慢增加,临界坡度>31°。

Slope is an important geomorphological factor. This paper firstly studied the impacts of slopes and maxi- mum 30-minute rainfall intensity （Ⅰ30） on soil erosion, and then determined the critical rainfall intensity between splash-sheet erosion and rill erosion, and finally studied the critical slopes and the slope gradient impact on soil e- rosion under different soil erosion types, using date of runoff plots in Chabagou and Wangjiagou Gully. The results showed that： first, the interaction between slopes and rainfall intensity impacts on soil erosion is obvious ,. influence of rainfall intensity on soil erosion increases with increase of slope ; second, the critical 130 between splash-sheet e- rosion and rill erosion in Tuanshangou Gully is not a fixed value, but fluctuates around 0. 31 mm/min on different underlying conditions. Third, while dominated by with a same tendency of soil erosion modulus and splash-sheep erosion, there is a critical gradient less than 31° runoff modulus changes according to gradient that soil erosion modulus increases first and then decreases with the slope changes from 9° to 31 ° ; while dominated by rill erosion, there is not a critical gradient, with a same tendency of soil erosion modulus change and runoff sediment change ac- cording to changing gradient that soil erosion modulus increase with the increase of slope from 9 ° to 31 °, aeritical gradient more than 31°.