汉江流域河网分级特征研究

为深入了解汉江流域河网结构特征, 在提取高精度数字河网的基础上, 结合地表水频率地图和河宽遥感数据集, 研究河网几何结构和拓扑结构的自相似性, 同时统计分析河网的河宽分级规律。结果表明, 河网中1~6级的分支比、河长比、面积比和侧枝比等结构参数稳定在较窄的数值范围内, 证明1~6级河网具有良好的几何拓扑结构自相似性。在河网自相似级别范围内, 河流级别与河宽平均值呈现近似指数分布, 1~6级的河宽比数值稳定, 平均值为1.87, 说明Horton定律适用于河宽分级。通过对比沟河识别前后的河网参数发现, 河长、河宽和流域面积越小, 河流越容易“干涸”, 并导致低级别河流偏离河网结构的自相似性。

Hierarchical Characteristics of River Network in Hanjiang Basin

The structural characteristics of river network in the Hanjiang basin were investigated based on the extracted high-precision digital river network. Combined with surface water frequency maps and river width remote sensing datasets, we analyzed the self-similarity of geometric and topological structure of the river network, as well as the hierarchical characteristics of river width. The results show that convergences of bifurcation ratio, river length ratio, area ratio, and side-branching ratio happen to rivers at stream-orders 1–6, which implies that geometric and topological self-similarity of river networks was fairly fitted at stream orders of 1–6. Moreover, the statistics of hierarchical characteristics of river width show that within the range of self-similar stream-orders, the average river width presents an approximate exponential distribution. The river width ratio is relatively stable at stream-orders 1-6 and the average value is 1.87, indicating that Horton’s law is applicable to river width. By comparing the river network parameters before and after exclusion of pseudo-rivers, it is found that rivers with smaller stream-order, length, width and basin area are more likely to dry up, leading to the deviations of the real river network from the structure of self-similarity.