DEM分辨率对大兴安岭林区水土流失评价结果的影响

Influence of DEM Resolution on Soil and Water Loss Evaluation in Daxing'an Mountains

为揭示数字化高程模型(DEM)分辨率对水土流失评价结果的影响,基于地理信息系统(GIS)和遥感技术(RS),利用不同分辨率(10、20、30、40、50、60、70、80、90、100 m)DEM,提取坡度因子(S)和坡长因子(L),并复合成地形因子(L_S),将L_S因子、降雨侵蚀力、土壤可侵蚀性、植被覆盖和管理与水土保持措施5个主要影响水土流失的因子,带入修正的通用土壤流失方程,得到不同分辨率下的土壤侵蚀量。分析不同DEM分辨率下,地形因子及水土流失评价结果的变化规律。结果表明:在研究区域内,土壤流失量对分辨率变化最为敏感,对L_S因子的敏感度大于S因子和L因子;DEM分辨率小于40 m时,土壤侵蚀量变化较小;当分辨率为50 m时,发生剧变,当分辨率超过60 m后逐渐趋于平稳。随着DEM分辨率的降低,其对水土流失评价结果影响也越来越小,因此可以认为最适宜水土流失评价的DEM分辨率应为50~60 m。利用50 m分辨率DEM计算的研究区域水土流失主要以微度和轻度侵蚀为主,占研究区域总面积的90%以上,水土流失较严重情况主要位于山脊和人类干扰较强烈地区。

In order to reveal the influence of Digital Terrain Model(DEM)resolution on water loss and soil erosion evaluation results,we extracted the slope factor(S),slope length factor(L)and combined these two factors into terrain factor(L S)based on the geographic information system(GIS)and remote sensing(RS)and different resolution DEM(10,20,30,40,50,60,70,80,90,100 m).Then we introduced five main factors affecting water loss and soil erosion into the modified generalized soil loss equation(RUSLE)to get soil and water loss under different DEM resolutions.Five main factors are L S,rainfall erosivity,soil erodibility,vegetation cover and management,and water and soil erosion factor.The soil loss is the most sensitive to DEM resolution change and the sensitivity of L S is greater than that of S and L in the study area.When the DEM resolution is lower than 40 m,the change of soil and water loss amount is small,when the DEM resolution is 50 m,the amount is great;when the DEM resolution is higher than 60 m,the amount tends to be stable.With the decrease of DEM resolution,its impact on soil and water loss results gets smaller.Therefore,50-60 m should be the most suitable DEM resolution for evaluating soil and water loss.Soil and water loss is dominated by slight and mild erosion accounting for 90%of the total area.The serious soil and water loss mainly occurs on the ridges and the region of intense human interference.