The Study Of Ecological Safety Analysis And Rational Design On The Urban Area Of Changsha City

The Changsha city locates at the alluvial plain formed by many rivers, and thus is flooded again and again. With the expansion of the city, the demand for flood control is increasing, which highlights the contradiction for limited lands. Meanwhile, the increase of population resources and environment caused a serious impact on the landscape eco-safety pattern of urban rivers.The paper carried out a more comprehensive study on-spot survey on the urban eco-safety of city rivers. Firstly, a survey on Xiangjiang River, Liuyang River, Laodao River, Longwang River, Jinjinag River, Guitang River, Baisha River and Sha River in the area of Changsha City showed that the eco-safety mainly focused on the performance of single habitat and the decline of biodiversity and ecological services; Secondly, a comprehensive analysis of ecosystem structure and function of ecological services in these two areas of damage causes, together with a comprehensive assessment of the security situation in Changsha city by the use of Meta-analysis came to the result of weight distribution; and then analyzed these results and put forward the decision to solve the river's ecological safety in Changsha city was put forward; Finally, based on the above analysis and results, made a target and task to restore the city rivers and put forward a rational idea to design the city rivers.To resolve the ecological security of urban river, a rational design idea called river regression design was proposed. River regression design is an instructional design, and its essence is to make the city river return to the one near the natural state through the means of supporting, and relies on the ecosystem of self-regulation and self-recovery function.Based on the theory in ecology, geomorphology, biology, water engineering and landscape science, the idea of self-design, succession, stream flow and flood square pulse theory was discussed to be the basement of the design. And the physical law, economic feasibility and esthetics were concluded as the basic principle followed in the design process. And several rational design models such as spur-dikes-shadows- deep pools model, natural-imitating model and indigenous plant array model was proposed to reproduce the meandering of urban rivers and the diversity of organism, and then to solve the landscape ecological security resulted from the linear stream of urban rivers and create a harmonious landscape ecological security pattern between human beings and water resources.As an illustration, the above theories were applied to the ecological landscape in the Laodao River district at the end of this paper. And the three design models in the illustration had been fully and flexibly applied making the river regression design been further interpretation.