不同土地利用方式坡面产流输沙过程模拟研究

针对目前多数坡面侵蚀预测模型难以模拟土地利用变化对坡面产流输沙过程影响的问题,基于运动波方程和泥沙输移公式,给出了一种能够反映不同土地利用方式下坡面产流输沙时空变化的简化模型,并利用裸地、草地、坡耕地、灌木地及幼林地的试验及自然降雨条件下坡面产流输沙实测资料对模型进行验证,符合较好.利用该模型对黄土高原不同降雨条件下不同土地利用场景坡面产流输沙特征进行了模拟,结果表明:典型降雨条件下,5 a树龄以上的林地或覆盖度在60％以上的草地坡面标准小区基本不再发生侵蚀；坡度小于15°的裸地坡面中下部发生轻度侵蚀；十年一遇降雨条件下,10 a树龄以上的林地坡面土壤侵蚀基本得到控制,而草地调控坡面水沙的能力有限,裸地更差.对低强度短历时降雨,草地调控水沙的见效较快；对高强度长历时降雨,林地调控水沙的作用较大,两者宜配合进行；对不同坡度裸地,要严格控制坡面坡长.研究结果为优化土地利用方式提供了理论支撑.

Numerical Simulation of Runoff Generation and Sediment Transport Processes Under Different Lands Use Patterns

In order to evaluate the effect of land use change on soil erosion process, a mathematical model was developed for simulating runoff generation and sediment transport processes on different slope lands. The model was comprised of two modules: the kinematic-wave equation for overland flow and a sediment transport formula. The measured runoff generation and sediment transport data of bare land, grassland, cropland, scrubs land and young forest land were used for model validation and the simulating values were in good agreement with the measured ones. Then the characteristics of runoff generation and sediment transport under different land use scenarios were predicted using the model and the results showed that soil erosion would be greatly controlled on 5-year-old forestland or grassland with coverage more than 60% under the normal rainfall in the loess plateau, and light erosion occurred in the middle and lower part of the bare land with the gradient less than 15°. Only the 10-year-old forestland could provide a good erosion control effect while that effects of grassland and bare land were limited under the once in ten-year rainfall. Both grassland and forestland should be cooperated in combating erosion by taking advantages of the faster effect of grassland for low intensity and short duration rainfall and the more obvious effect of forestland for high intensity and long duration rains. The slope length should be strictly controlled for bare land with different gradients.