The Study Of River Ecological Restoration Technology Based On The Near-natural Design

In this paper, the theory and technologies of river rehabilitation at home and abroad were reviewed. In conjunction with this specific natural conditions (drinking water source in Changchun city), a scheme considering about the local conditions is draw up and applied on the ecological restoration program which is about the damaged rivercourse in Mount Lianhua located at Changchun city.The project began on April 28, 2008, completed in october 30, 2008. Under the coordination of a unified department at all levels, it takes 6 months to build a "zero-cement ecology river with a length of 1000 meters ".Natural materials such as riprap, wooden blocks, various plants were used in the project; concepts of flood control, landscape, hydrophilic and ecosystem protection were considered; The technology of bio-ecological restoration, habitat restoration, aquatic biological community restoration were also considered.After the restoration, verification about the ecological river from safety of the river engineering, hydrological process, physical habitat, hydrophilcity ,ecological effects, visual effects and other aspects were carried out.The results show that:(1) After several floods, 2008.6.30, 2008.7.9, 2008.7.16, 2008.7.29 etc. The result shows that the ecological river fully meets the needs of the safty on flood. The river bank protection works has ensured the safety of people's lives and property.(2) During flood season, ecological rivercourse can buffer the power of floods, reduce erosion intensity on the river. During dry season, ecological rivercourse can accumulate water, making the river on the condition of not being too dry or water interception, to maintain the integrity of the river hydrological processes. A series of measures of ecological restoration were used to increase the range of flow velocity and water depth.The original river flow rates range of levellers period from 0.12m / s to 0.34m / s, flow range of flood period from 0.97 m / s to 1.41m / s.After restoration, the flow velocity range of levellers period from 0m / s to 0.48m / s, flow range of flood period from 0.09 m / s to 1.27m / s. The original river-flow water depths range of levellers period from 0.16 m to 0.34m, water depths ranging of flood period from0.31 m to 0.46m. After restoration, the water depths range of levellers'period is from 0.05 m to 0.57m, water depths range of flood period is from 0.19 m to 0.72m.(3) After restoration, the river bed substrate suitability indices were increased. The index of river bed substrate suitability of A-1 area, A-2 area, A-3 area has changed from the original numerical value 0.20, 0.17, and 0.18 to 0.31, 0.35, 0.38. However, the index of river bed substrate suitability of unrepaired area changed little. (4) The diversity index of vegetation and benthonic animal on restoration area (A-1, A-2, A-3) are higher than the diversity index of unrepaired area (area B). The number and frequency of the large animals such as fish, frog, snake in repaired area are higher than in unrepaired area(area B).(5) After the repair, by reducing bank slope, paveing trail along the river, setting the hydrophilic step, building the embankments and hydrophilic platform for the purpose of entertainment and other measures, the hydrophilicity of the river has increased remarkably.(6) After the restoration, the recognition degree of the landscape was changed from negative to positive. The landscape of typical restored ecological river is much better than the landscape of typical urban river which is not repaired. The results show that the recognition degree of the landscape has been admitted by the people.. Large wetland and small wetland obtain the highest recognition, because these two regions have artificial wetlands which form a larger area of the waterfront landscape.