Abstract:The evolution characteristics of river system in the central urban area of Shanghai since 1950, and the evolution effects on water system connectivity and urban water safety are diagnosed by using the landscape ecological theory and GIS spatial analysis. The study shows that (1) the use of connectivity indexes of corridor connection rate and loop index in landscape ecological method can better diagnose the structural characteristics and evolution process of high-density network water system in river network areas. In the four typical river network connectivity indicators, the loop index is more sensitive to the evolution of the water system structure. (2) The river network density of the central urban area of Shanghai has declined by 68.54% in the recent 70 years. The most extinct rivers less than 1 km in length are the village-level rivers and are accounted for 77.13% of the total extinct rivers. (3) Before 1994, the connectivity index of regional river system was higher than 1. And then it started going below 1, and the loop index of river system decreased sharply. The central urban area of Shanghai basically no longer has the characteristics of the typical network river system structure. (4) The atrophy of river network leads to the sharp decrease of water surface rate and the obstruction of river network connection. In the recent 70 years, the enhanced drainage capacity of rainwater pumping stations has a significant response relationship with the total length of the river network and the change of river network connectivity, in which the response to the change in the total length of the river network is more obvious.
