Study On The Characteristics Of River Network Changes And Its Protection Under Rapid Urbanization In Pudong New Area

The problems of river networks damage and its function degradation under rapid urbanization have become ever more prominent in plain river network region. Study on the characteristics of river network changes and protection measures for river networks structure and its function have become the research focus in the field of river system conservation and management. Moreover, study on the environment significance of river network,the landscape features of river system and its intrinsic relationship with the regional landscape pattern have important theoretical and practical significance to the urban landscape planning and construction. From an integrated perspective of geomorphology of rivers, landscape ecology and environmental management, based on the review of developing of regional urbanization and water quality evolution, the spatial and temporal characteristics of river network changes under rapid urbanization were exposited and analyzed systematically, taking Pudong New Area in Shanghai as an empirical study area in this paper.And then, the effects river network changes may produce on the landscape pattern during long time scale were discussed from different spatial scales, which were riparian terrestrial landscape and whole region landscape respectively. Finally, adaptive management strategies for river networks protection in different stages of urbanization were put forward in thesis from the following main headings.(1) Six indicators including surface water ratio(Wp),the density of rivers(Rd), distribution frequency of river(Rf) and the integrity and complexity of river network(Rc), average branching ratio of rivers(Rb), developing coefficient of branch rivers(Rz) were selected to quantitively describe the characteristics of river networks changes in Pudong New Area for nealy 40 years, based on an integrated multi-indicators, multi-scale and multi-temporal methods.Morever, the difference of river networks morphology and structure in different urbanization level were futher analysed and compared. Research findings showed that:①River networks has experienced three changing phases:Trunk rivers man-made modifying and branch rivers decling(1965～1989), sharp reducing of tributary(1989～2000) and slowing down of tributaries decline (2000～2006), characterized by the disappearance of branch rivers in suburb region. River networks experienced the changes from a natural river networks crisscrossing with highly dense mainstream and tributaries into a simplified river networks characterized by only mainstream and highly reduced branch river.②River networks have been changing with a typical spatial and temporal features:on the time scale, the value of river networks indicators tended to reduce year by year, showing that the changes of river morphology and structure didn't comply with the law of nature; on the spatial scale, river networks changes showed a spatial difference, the original river networks have been damaged in highly urbanized region and ramian a nealy natural morphology and structure on the fringes of urbanization region.③City construction activities were the directive causes of river rapid reduction tendency, the building of industrial zone, road and municipal works, and construction of residential district and other construction activity were the main drivers of river networks reduction, and road building and residential district expansion may be the direct causes of river networks reduction on the fringe of urbanization region.(2)Integrated methods including correlation analysis, water quality assessment, and landscape index were used in this paper, to analysis the changes of water quality and river system structure, and further discuss the impact river network changes may produce on the water landscape,terrestrial landscape and regional landscape under rapid urbanization. The results showed that:①Water quality was significantly affected under the rapid process of urbanization, river water quality in the higher grade was generally better than a river in lower grade; Water quality in fringe areas of urbanization was generally better than the urbanizing region; Terrestrial landscape changes characterized by the increase of industrial land, road traffic land and residential landscape.②The area, number and have reduced apparently, as a result, dominance of water patch in the region landscape also decreased, the connectivity of river network also got disrupted.③River networks change impacted the distribution and complexity of other landscape pattern, and every patche showed a tendency of equalizing and mixing with other patches.(3)Based on the identification of key issues on the changes of river networks in Pudong New Area, controlling indicators were put forword to protect river networks from different spatial scales and time stages, and an attempt study on the adaptive management countermeasures to the river system was proposed in Pudong New Area, the results concluded that:①Different controlling requrirements for indicators, including surface water ratio(Wp),the density of rivers(Rd), developing coefficient of branch rivers(Rz) were proposed in the highly urbanized region and suburban region.②Taking the development characteristics of different urbanization stage as a factor for consideration, combing controlling indicators with other environmental protection system planning and management, from the macro, meso and micro scale respectively, the proposals to control and adjust the controlling indicators and management countermeasures at the right time was brought forward finally in this paper, and an tracking evaluation on the river networks changes in half-urbanized region and fringe areas of urban indicators was proposed.③It was proposed that some countermesures should be taken to preserve and restore natural landscape in surburban region by exchange the culvert with bridge and improve the connectitvity of river system and fluidity of water body;and for theprotection of river system in highly urbanized region, it was suggested that the building of human cultural landscape and natural landscape function should be enhanced, based on regional characteristics of green corridor of riparian zone,expecting to give full play to the environmental and ecological function.