A Study On A Demonstration Project For Ecological Restoration Of Ditches At QianWei Village, Chongming County

To achieve a harmony between human being and the nature is becoming a hot topic worldwide in the recent decades, and ecological rehabilitation of rivers appears to be one of these tasks. There have been many studies focused on ecological rehabilitation of river systems both in the rural and urban areas as a growing demand on better living and ecological environments in the recent years. The restoration of river systems has been developed from the traditional measures of pure engineering to the measures combined the traditional one with the ecological engineering. The ditches in rural areas have been usually considered only as a drainage and irrigation channel, instead acting as an important wetland and corridor system which has many ecological and environmental benefits.As a large alluvial island in the Yangtze River Estuary, The ChongMing Island has a dense river network which plays an important role in the whole island. As a consequence of rapid urbanization, there have been many ecological problems in ChongMing Island such as water pollution, degradation of ecological functions such as damages in river habitats and biological corridors. These problems was serious in QianWei Village, ChongMing Island which was becoming a growing threaten to the living and water environments. In this study, we designed and performed a demonstration project for the ecological rehabilitation of ditches in Qianwei village which may become a feasible model for the Chongming Island as well as for other areas in similar conditions.Based on a survey for the study area, we made a synthetic plan for the demonstration project. By constructing an ecological drainage from land to water body, the possible pollutants from scattered points and non-point sources could be intercepted and purified, and the ditch had a function of purifying water and improving aesthetics. The demonstration project was implemented by using the biological slope-protection techniques called soil bioengineering to stabilize the ditch bank, and using the zeolite system and the oxidation pond system to purify the ditch water.The assessment on the project was made via a runoff simulation experiment and the measurements of parameters such as soil shear strength, biodiversity, and ditch water quality. The results showed that the ditch slopes restored by soil bioengineering could significantly enhance the soil shear strength, compactness and moisture content, and the formed vegetation had significant effects on retarding runoff and removing TSS (P<0.05). Applying live fascines could significantly increase soil shear strength and TSS removal rate (P<0.05), but its effects on increasing soil compactness and moisture content and retarding runoff were not significant. After the implement of the demonstration project, the total concentrations of N and TP in ditch water were decreased significantly, while the aesthetic value and biodiversity of the ditch slope were improved greatly. The integration of biological techniques with other ecological restoration measures could stabilize ditch slopes and improve the ditch habitats. The results of measurement indicated that the vegetation on the restored slope could effectively mitigate the erosive effect of rainfall runoff. The content of organic matter and water stable aggregate (r>0.25mm) in soils were increased significantly (P<0.05), which had a significant relationship between them.Soil bioengineering is the use of living plant materials to construct structures that perform some engineering and ecological functions and can provide an effective means for slope stabilization and site restoration of riverbanks. The integration of biological techniques with other ecological restoration measures is effective and applicable to the rural area. The ecological ditch after restoration in Qianwei village, Chongming Island achieved a coordination among the ditch reconstruction, water purification, habitat restoration and landscape building, according to the rule of harmony between man and nature,. It has been proved to achieve the goal of ecological construction of water body, which is clear, green, unblocked and pleasing.