为更加准确判定流域水系最佳集水面积阈值,以陕西省安塞县纸坊沟流域30 m DEM为例,采用均值变点分析方法对流域水系分维值、DEM分辨率与集水面积阈值之间的关系进行了分析。结果 表明:(1)集水面积阈值与分维值的关系:不同分辨率DEM,随着集水面积阈值的增加,分维值呈先增后减趋势,且其下降速度由急剧变为缓慢;(2)DEM分辨率与分维值的关系:在最佳集水面积阈值条件下,随着DEM分辨率的减小,分维值整体趋于下降,且其下降速度越来越缓慢;(3)纸坊沟流域水系分维值为1.20,所对应的最佳集水面积阈值、DEM分辨率分别为100,15 m。均值变点分析方法可用于最佳集水面积阈值和DEM分辨率的快速确定,且可靠性较高,判定系数达0.99。研究结果为流域河网水系提取时集水面积阈值的确定提供了方法参考依据。
In order to determine the optimal catchment area threshold of catchment accurately, 30 m DEM of Zhifanggou Catchment located in Ansai County of Shaanxi Province was taken as the example. And the mean change point analysis method was used to analyze the relationships between catchment fractal dimension, DEM resolution and catchment area threshold. The results show that:(1)the relationship between the catchment area threshold and fractal dimension presents that the fractal dimension value increases first and then decreases and its rate of decline changes from rapidness to slowness with the increase of the catchment area threshold under different resolutions of DEM;(2)the relationship between DEM resolution and fractal dimension value indicates that the fractal dimension value tends to decrease as a whole and its rate of decrease is getting slower and slower with the decrease of DEM resolution under the threshold of optimal water catchment area;(3)the box fractal dimension of the drainage system of the Zhifanggou catchment is 1.20, the corresponding value of optimal catchment area threshold and the optimal DEM resolution are 100 m and 15 m, respectively; the mean change point analysis method is more accurate and reliable for determining the optimal catchment area threshold and the optimal DEM resolution and decision coefficient reaches up to 0.99. These research results can provide the references for determining the optimal catchment area threshold of other river network water system extraction.
