基于四种分辨率DEM的侵蚀模型地形因子差异分析

通过提取江西省兴国县潋水河流域10 m、25 m、50 m和100 m四种分辨率数字高程模型(DEM,Digital Elevation Model)的坡度、坡长因子,在GIS数字地形分析和数理分析等方法支持下,研究不同分辨率DEM计算坡度坡长组合因子(LS)的精度差异。结果表明:(1)基于4种分辨率DEM提取的坡度结果存在明显差异,随分辨率的降低,坡度整体变缓,DEM精度越低,对地形的概括作用越大,100 m分辨率DEM平均坡度降为10m分辨率DEM平均坡度的45.04%。(2)流域坡长以0~80 m的短坡为主,随着分辨率的降低,地面坡长明显整体延伸。(3)不同分辨率DEM计算的LS因子平均值变化范围为6.10~7.10,坡度和坡长的组合消弱了单一坡度和坡长的影响,随着地形起伏程度增大,在LS因子计算过程中,坡度的主导作用越来越弱,坡长的主导作用越来越强。

Geomorphic factors in DEM-based soil erosion models as affected by resolution

Gradients and lengths of the slopes in the Lianshui River Basin, Xingguo County, Jiangxi Province were extracted using DEMs different in resolution, i.e. 10m, 25m, 50m and 100m, and analyzed for difference in accuracy difference between the DEMs in calculating the combined gradient and length, using the GIS digital terrain analysis method and the mathematical analysis method. Results show that 1) significant differences exist between slope gradients obtained by DEMs different in resolution, indicating that the gradient decreases with declining resolution and that the lower the accuracy, the greater the generalized effect on terrain information; and that the mean slope gradient obtained by DEM 100m in resolution is only 45.04% of that by DEM 10m in resolution;. 2) the slopes in the valley vary in length mainly in the range of 0~80m and their lengths elongate with declining resolution; and 3) the mean LS factor values obtained by the DEMs regardless of resolution vary in the range from 6.10 to 7.10; the combination of slope gradient and slope length factors reduces the effects of single slope gradient or single slope length factor; and as the topographic fluctuation increases in extent, the dominating role in LS factor shifts from slope gradient to slope length.