Abstract
Large quantity of rivers have disappeared during rapid urbanization in China’s Yangtze River Delta, and it is difficult to define the changes in the river network owing to its high dense and complex reticular structure. Shanghai’s Pudong New Area (SPNA) is a typical area of rapid urbanization in the delta. A Comprehensive River-network Indicator System (CRIS), including quantity and area, geomorphologic structure, and landscape connectivity indicators, was established to characterize the changes in the dense reticular river network in SPNA from 1965 to 2010. The percentage of urban area rapidly increased from 22.52% to 59.49% in SPNA, whereas that of water surface (Wp) decreased from 10.57% to 7.23% during the same period. The changes in river network displayed a clear spatial gradient, and the closer the functional area is to the city center, the earlier and faster the changes in the rivers. CRIS obviously changed when the percentage of built-up area increased from 10% to 30%; however, the CRIS changed more gently when the percentage exceeded 30%. Among the three sub-indicators of CRIS, quantity and area strongly corresponded to urbanization stages, geomorphologic structure was most sensitive to urbanization, and landscape connectivity accurately captured the threshold phenomena in the change in reticular river network.
Highlights
A reticular river network often appears on alluvial plains near estuaries, such as the Yangtze Delta in China, Mississippi Delta in the United States, and Ganges Delta in India
Taking s Pudong New Area (SPNA) as a case, this study investigated the impact of urbanization on river network during the period from 1965 to 2010, analyzed the sensitivity of different river network indicators to urbanization and the differences in the performance of these indicators at different stages of urbanization and functional area scale
We proposed the use of Comprehensive River-network Indicator System (CRIS), including quantity and area, geomorphologic structure, and landscape connectivity indicators, to analyze spatiotemporal variation of the reticular river network change in SPNA, which is one of the most rapid urbanization areas in China
Summary
A reticular river network often appears on alluvial plains near estuaries, such as the Yangtze Delta in China, Mississippi Delta in the United States, and Ganges Delta in India. Rapid urbanization in China has greatly impacted river networks, especially after the 1980s. Traditional indicators may be divided into two categories: quantitative category, such as water area percentage (Wp), river density (Rd), and river frequency (Rf), and geomorphologic category such as branch ratio (Rb). These indicators have been widely used in research on river hydrology and watershed geomorphology for decades [9,10,11,12,13]
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