Research On Near-naturalization Of Urban Channelized Rivers

The urbanization and the flood disasters have led to the severely channelized rivers, with the loss of the functions of dynamic process and ecological service of the rivers. There has been a great demand for the near-naturalization of the urban channelized rivers due to the renewal of old cities and the river landscapes, and the demand for ecological environment by the changing ideology. However, the river design has been oriented by flood control, which omits the interaction between human beings and the nature, the fusion of the city and the water systems, and the cooperation of the ecology and the technologies.Bridging the professional knowledge of landscape spaces, ecological system and social humanity, landscape architecture can play a significant role in the process of river near-naturalization. This dissertation discovers the near-naturalization strategies of the urban channelized rivers, so as to restore the connection of urban rivers and the nature and to balance the city and the nature.This dissertation puts forward for the first time the "Macro-meso-micro" multi-scale perspective. After understanding the morphological characteristics and the automatism process of the rivers at the above three scales, the near-naturalization strategies have been proposed. At the macro scale, urban rivers are part of the natural drainage basin. Referring to the ecological metropolis ideology and the river ecology ideology, four strategies of urban river near-naturalization have been presented and applied in analyzing many successful cases in foreign countries, including the ecological flood control security policy, relatively continuous space strategy, the boundary integration strategy, and the multi-level landscape stepping in strategyAt the meso scale, the urban channelized rivers have been classified into three types and corresponding strategies have been put forward, that is, urban compact river way, urban elastic river way and new urban river way. Each strategy has relative measures which have been demonstrated in the typical cases. Urban compact river way strategy includes selective spatial extension, ecological floating island, shallow water way, revetment softening. Urban elastic river way strategy includes rebuilding the river levee form, shaping flooding plain, dredging river way form increasing habitat islands, creating divarication, etc. The new urban river way strategy includes designing the river way form, elastic flood storage, building flooding plain, rebuilding river levee form, flood safety warning, etc. Based on the above, the river way model verification methods are given, to verify the feasibility of the near natural river way and to modify combining the water dynamic experiment and water flow analog calculation model. At the micro scale, near-naturalization strategies are based on the river automatism process, ecological revetment treatment and river way plants selection. A list of the measures has been compiled.Furthermore, given the issue of channelized rivers in the fast urbanization process in China, this study has discussed the history of river governance, analyzing the motivations and the dilemmas, especially the drawbacks of related laws, policies and mechanism, and gathered the related experiences in terms of water treatment in Europe, US and Singapore. Finally the urban river near-naturalization strategies at the macro and meso scales are poposed. The macro strategies take the urban ecological network as the breakthrough point. The meso strategies are modular. Multiple disciplines and parties’participation oriented by landscape architechture. The incentive mechanism features the benign urban development driven by rivers. And the five steps of implementation have been proposed, so as to facilitate the reforms of urban river near-naturalization in China. The five steps are general planning and actions planning, securing the sources of funds, bids inviting in units of river sections, construction and later period detection, and appraisal and modification.