汇流阈值拟合分段及沟谷级别对黄土典型小流域盒维数的影响

Influence of Watershed Concentration Threshold Fitting Segmentation and Gully Level on Box Dimension of Typical Small Watershed in Loess Plateau

采用分维方法刻画沟谷形态特征是定量沟谷差异的有效手段之一,然而流域上中下游形态存在差异,沟谷等级如何影响沟谷盒维数仍有待探讨。基于1∶1万DEM数据源,对陕北黄土高原绥德典型小流域沟谷的全局和分段盒维数进行研究,并对比分析了一级支流的全局和分段盒维数。结果表明:小流域范围内,不同汇流阈值对应的沟谷盒维数随阈值的不同在一定范围内波动,阈值为200和1800的沟谷盒维数分别为1.48和1.23;小流域上游盒维数分别为1.07和1.02,对应沟谷发育初期;中下游盒维数增大,均为1.66,对应沟谷壮年期。一级支流全局盒维数低于全流域盒维数,分别为1.29和1.08,位于流域上游的一级支流盒维数最小,分别为0.87和0.94。研究表明,盒维数法能一定程度上揭示沟谷形态差异。

Fractal dimension method is one of the effective methods to quantify the valley differences.However,there are differences in the upstream,middle and downstream of the valley.How the valley level affects the box dimension of the valley remains to be explored.Based on 1∶10000 DEM data source,the global and segmented box dimensions of Suide small valley in the Loess Plateau of Northern Shaanxi Province were studied,and the global and segmented box dimensions of the primary tributary were compared and analyzed.The results showed that:in small watershed,the box dimensions of different confluence thresholds fluctuated in a certain range with different thresholds,the box dimensions of 200 and 1800 thresholds were 1.48 and 1.23,respectively;the box dimensions of the upper reaches of small watershed were 1.07 and 1.02,respectively,which corresponded to the early stage of valley development;the box dimensions of the middle and lower reaches increased,which were all 1.66,which corresponded to the peak age of valley.The global box dimension of the first tributary was lower than that of the whole watershed,which was 1.29 and 1.08 respectively.The box dimension of the first tributary located in the upper reaches of the watershed was the smallest,which was 0.87 and 0.94 respectively.The results showed that the box dimension method could reveal the differences of gully morphology to a certain extent.