The response of river network structure to urbanization: A multifractal perspective

Abstract

Multifractal analysis has been applied as a pattern recognition method based on numerical verification. The approach was successfully used to estimate the river network structure in previous research but has been seldom used in temporal analyses. The Lower Qinhuai basin, which is located in the lower part of the Yangtze River Delta, was chosen as the study area. In order to analyze the morphological characteristics of river network, to determine their spatial and temporal variations, and to discriminate the prevailing forces of the variations from the 1960s–1980s and 2010s, the remote sensing images, topographic data, digital line graphs and statistical data of the study area were collected. Based on ERDAS 9.3 and ArcGIS 10.2, the river network data were reconstructed, and multifractal analysis was performed. The results demonstrated that the capacity dimension of the river network decreased from 1.67 to 1.60 and then to 1.59 from the 1960s–1980s and 2010s. The sub-basins with relatively high river densities dominated the multifractal structure. Additionally, the main rivers and tributaries were on increasing trend in filling capacity and spatial heterogeneity respectively, and they jointly determined the multifractal features of the river networks. Urbanization process, instead of morphology or lithology force, was confirmed as the main driving factor of the multifractal structural dynamics of the river network in the basin and sub-basins in decades scale. The results would provide solid support for the river conservancy and urban planning, and finally promote the sustainable development of the “water-society” system.