Dynamic Changes of River Network under Intensive Human Activities: A Case of Pudong New Area, Shanghai Municipality
高强度人类活动下河网水系时空变化分析

River network protection is not paid enough attention in the process of rapid urbanization,leading to riverway tamping,river network reduction and water environment destruction.Moreover,there are few relevant researches on spatial-temporal change mechanism of river network caused by intensive human activities.This research attempted to reveal the dynamic change trends and spatialtemporal distribution characteristics of river network in Pudong New Area by depicting and analyzing the intensity of river loss and relating transformation modes based on the multi-temporal remote sensing data of aero photographs and relevant social-economic statistics.Firstly,the water quantity in Pudong New Area has experienced dramatic changes with the remarkable reduction of water body and the density of river network from 2000 to 2003.For instance,in these three years,the total net reduction of river body is 449 hm~2 with an annual reduction rate of 4%;and the average reduction rate of river density is 5%.The transformation from water body to urban land use acted as the main contributions to the changes of both quantity and density of river network.Secondly,different urbanization levels and speeds have different effects on the river network.The disappeared rivers are mainly located in the urban fringe and near to the major roads,where the urbanization is intense,reflecting the violent encroachment of urbanization to river network.Quite on the contrary,the water body located in the downtown didn't experience the dramatic changes,and in some remote areas which featuring a relative slow constructional land growth,the intensity of river network changed little.Thirdly,the regional differentiation of decrease in river network is obvious.It can be concluded that the major parts of river network losses are mainly located in the intersectional of urban and suburban areas.The distinct trends of the decrease in river network appear by turns with the distance increases from the downtown,which means it changes from very slow to fast,very fast,slow,then to very slow,reflecting a close relationship between the urbanization level and urbanization speed with the river network decreasing speed.