Changes in river networks and their storage and regulation capacities in the Rapidly Urbanized Taihu Basin, China

Abstract

Owing to the crucial environmental and hydrological functions of river systems and intensive human disturbance, further investigations of their change patterns and flood control functions are urgently needed. The Rapidly Urbanized Taihu Basin (RUTB) was selected as the study region to investigate changes in the river networks, the relationship between changes in river systems and urbanization, and the changes in the static drainage storage capacity (SC) and regulation capacity (RC) from the 1980s to the 2010s. The results indicated that the total drainage density in RUTB decreased by 10.17%. For the first-, second-, and third-order rivers, the changes are +7.61%, −14.35%, and −17.84%, respectively. Spatially, the change pattern of the third-order river drainage density displayed significant spatial clustering. The ratio of main to tributary river length (Rmt) was increased from 0.31 in the 1980s to 0.39 in the 2010s. Spatially, the drastic increases were found in the south-east of Wu-Cheng-Xi-Yu, the east of Yang-Cheng-Dian-Mao, and the central southern part of Hang-Jia-Hu. Results moreover show that urbanization has the greatest influence on the third-order drainage density, especially around the secondary and rapidly developing cities. The demand for flood control has led to a slight increase in the density of main rivers. The values of SC and RC decreased by 0.69% and 40.61% in RUTB, respectively. These changes were mainly concentrated around the major cities and urban corridors. The decrease in SC was caused by the decay of the river system, and the reduction in RC was caused by a combination of river system degradation and increase in ordinary water levels.

Analyzing the impact of polder‐type flood control pattern on river system's regulation and storage capacity under urbanization

“…By constructing a hydrological–hydrodynamic model and evaluating the dynamic regulation and storage capacity during the flood season, we found that the polder‐type flood control pattern reduces the regulation and storage function of the river system, which adversely affects the dynamic regulation and storage capacity. Previous studies have shown that as urbanization has accelerated in recent years, the regional runoff yield has subsequently increased, and static regulation and storage capacity has dramatically declined (Gao et al, 2018; Lei et al, 2022; Xu, Xu, et al, 2018). Although the construction of polders has reduced the probability of waterlogging in the polder area, it has also reduced the regulation and storage of the river system for flooding and increased the potential regional damage to the ecological system and the flood risk (Harbul'akova et al, 2017; Laks & Walczak, 2020; Xu & Liu, 2019).…”

“…These studies neglect the impact on the river system's static regulation and storage capacity (Huo et al, 2020; Rahmati et al, 2020; Yang et al, 2016). Rapid urbanization will inevitably cause changes in the structure of the river system in the basin, which, in turn, will harm the connectivity of the river network and the static regulation and storage capacity of the river system (Gao et al, 2020; Xu, Xu, et al, 2018; Yuan et al, 2020).…”

Spatial Variations and Influencing Factors of River Networks in River Basins of China

“…Considering the fluctuation of meteorological data, the meteorological data of 2015, which is close to the average of a normal year, was chosen for this case. Mean population density and GDP were chosen as human activity indicators [23], with data from the Urban Statistics Yearbook. These four impact indicators were applied to carry out correlation analysis of river network characteristics in the study area.…”

“…Shao et al found that an increase the number of reservoirs in the Pearl River basin reduced the connectivity of the river network [21]. Lin et al and Xu et al found that, influenced by urbanization, the Yangtze River basin river networks 2 of 14 in the downstream showed a local increase in overall surface ratio and drainage density, and an overall decrease [22,23]. However, most studies have focused on individual river networks, and few studies have analyzed spatial variation in river network characteristics across multiple river basins [24,25].…”

Use of Fuzzy Analytic Hierarchy Process and Environmental Gini Coefficient for Allocation of Regional Flood Drainage Rights

“…According to the principle of index selection, the expert consultation method is adopted to screen the indexes and determine the four factors, which are natural conditions, level of social development, level of economic development, and technology and management. These factors are directly related to the total amount allocation of each control unit [45]. The above four factors constitute the criterion layer of the FAHP index system.…”