基于DEM的坡形与水土流失的关系——以西溪小流域为研究区

Relationship between slope shape and soil and water loss: A case study of Xixi catchment watershed

关键词:  水土流失  坡形  DEM  坡度  坡长

Key words:  soil and water loss (SWL)  slope shape  DEM  slope gradient  slope length

摘要:

为探讨对水土保持及生态环境的保护具有重要意义的坡形与水土流失关系，弥补以往多基于小区或室内试验的代表性不足，以DEM为基础数据，在现有P指数的基础上构建了表征纵向坡形的P_v指数，并以西溪流域中的小流域为研究区域，分析坡形-水土流失关系。结果表明：1）P_v指数表征的坡形-水土流失关系更符合小区试验结果，因此在量化纵向坡形方面更合理；2）总体上，直线坡的水土流失强度最大，然后向凸形坡和凹形坡的方向递减，且凸形坡的水土流失强度大于凹形坡，但坡度<15°时，直线坡的水土流失强度降为最小，向两侧递增；3）坡形对水土流失的作用小于坡度、大于坡长，且坡度为25°~35°、坡长为30~50 m时该作用最显著；3）坡形对水土流失的作用主要集中在微凸坡和微凹坡与直线坡之间，其他坡形对水土流失的作用较小，因此P_v为-0.4~-0.2和0.2~0.4时改造坡形对防止水土流失的收效最佳。

Abstract:

The study the relationship between slope shape and Soil and Water Loss (SWL) taking DEM as main data, P_v index representing profile slope shape is established on the basis of P index, and then taking a catchment in Xixi watershed as the study area to research the relationship between slope shape and SWL. The results show that:1) The rationality of P_v index on representing profile slope shape is confirmed by comparing with previous studies which based on plot or artificial rainfall experiments. 2) The relationship between slope shape and SWL generally shows SWL at uniform slope is the greatest and descends following the direction of convex slope and concave slope. SWL at convex slope is greater than that at concave slope. However, there is an exception that SWL at uniform slope is the smallest when slope gradient lower than 15° and increases following the direction of convex slope and concave slope. 3) The effort of slope shape on SWL is less than slope gradient and greater than slope length, which is the most significant when slope gradient within 25°-35ånd slope length within 30-50 m. 4) The effect of slope shape on SWL is more significant when between micro convex slope and micro concave slope, while the effect at other shapes is more obscure, therefore, transformation slope shape when P_v within -0.4——0.2 or 0.2-0.4 is the most effective for water and soil conservation. The results can provide a novel way to study the relationship between slope shape and SWL, which is also helpful for the prevention and control on SWL.