Effect of urbanization on the river network structure and functions-A case study in Suzhou City

Abstract

This paper centers on a series of urban hydrological problems like flood and waterlogging disasters resulting from the impacts of urbanization on river network structure. In this paper, Suzhou City, one of the typical plain river network areas in China, is taken as an object of the study. Based on different stages of urbanization, Suzhou City is divided into main urban district, municipal district and other county-level district. This research conducts both qualitative and quantitative analysis with the help of the remote sensing images in 1991, 2001 and 2015, as well as the stream data in 1960s, 1980s and 2010s, focusing on the influence of urbanization on the river network structure and functions. The study shows that: With the rapid development of urbanization, urban space continues to expand at the expense of farmland and water area primarily. The proportion of urban land in Suzhou City has reached 41.35% by 2015. The change rules of land-use type are basically consistent with different stages of urbanization. The change of river system structure is mainly affected by urbanization, which remains synchronized with such process. In the past 50 years, water rate, drainage density, tributary development coefficient, river area length ratio, drainage complexity, and drainage network structure stability have decreased by 19.63%, 6.91%, 7.34%, 1.06%, 5.49% and 7.87%, respectively in Suzhou City. Also, there exists negative correlations between urbanization level and each index. Human activities not only directly affect the functions of rivers, but also change the functions of rivers indirectly by changing the river system structure of the plain river network. The study serves as reference and theoretical support for the protection of river system and the flood control in urban areas.