基于不同分辨率DEM提取坡长的统计分布

Statistical Distribution of Slope Length Derived from DEM With Different Spatial Resolutions

坡长是土壤侵蚀和流域水文等研究的重要地形指标,在流域或区域土壤侵蚀评价研究中,坡长通常基于中低分辨率DEM提取,但随着DEM分辨率的降低,其上提取的坡长发生扩张,进而影响土壤侵蚀评价的计算精度。DEM分辨率对坡长的影响虽已受到注意,但对于这种影响的机理尚不清楚。因此本研究采用对坡长表面采用分级研究的方法,分析了坡长随DEM分辨率的统计分布变化的规律。结果表明:随着分辨率的降低,整体上表现为短坡长向中等坡长区扩张,长坡长出现衰减,坡长整体集中分布在中等坡长区域,基于此提出了因分辨率降低引起坡长表面变化的定量表述公式及坡长误差经验公式,可以根据坡长提取精度需求来计算合适的分辨率参数,为选取合适的DEM分辨率提高坡长计算效率提供依据。

Slope length is an important terrain factor in the research of soil erosion and watershed hydrology, etc. In the research of soil erosion assessment at watershed or regional scale, slope length is normally extracted from coarser resolution DEMs. However, slope length tends to increase as resolution becomes coarser, which makes the accuracy of hydrology and soil erosion model declined. At present, effects of DEM resolution on slope length has been received attention, but the mechanism for these effects is unclear. Based on this, we used the method of grading the surface of slope length to analyze the statistical distribution of slope length changes with DEM spatial resolution. The results showed that with the resolution decreasing the slope length classification surface presented different trends, the overall performance was that the short slope length grade expanded to the medium grade area, the high grade slope length appeared attenuating and the slope length centrally distributed in the medium grade area. Based on this, the quantitative expression of the slope length surface changes caused by the resolution reduction was proposed. The formula and the empirical formula of slope length error may calculate the appropriate resolution parameters according to the requirement of the slope length extraction precision, and provide the basis for selecting the appropriate DEM resolution to improve the calculation efficiency.