| As an important component of the riparian zone,in possession of many significantly hydrological,ecological,aesthetic and socio-economic functions, riparian vegetation buffer is a common concept of the riparian zone research and management in Europe and the United States.Within the process of riparian zone ecosystem management,in quest of an appropriate width of riparian buffer vegetation for achieving optimal riparian buffer zone ecosystem services becomes a key issue.As a result of different research areas,which has different climate,hydrology,soil,plants, landforms and types of pollutants,or even different sections of the river within the same region there are also some differences,and consequently the optimum width of riparian vegetation buffer is not different,it must be determined by the site conditions of the riparian zone.In this paper,taking Chongming Island in Shanghai as an example,choosing 33 backbone rivers in Chongming Island for studying,discussing the landscape pattern characteristics of the backbone riparian vegetation buffer,provide the basis for the planning of the riparian vegetation buffer in Chongming Island.For the south and north horizontal river,combined with the revised detention time model and hydraulic model to calculate the minimum width of riparian vegetation buffer required by the land parcel in riparian zone,based on geographic information system software,under different planning scenarios to simulate the variable width of riparian vegetation buffer.Finally,comparing the simulation result of riparian vegetation buffer with the landscape pattern characteristics present status,put forward planning proposals and measures of the south and north horizontal riparian vegetation buffer in Chongming Island.The main conclusions are summarized as follows:(1) From the perspective of planning and design,the revised detention time model and hydraulic model could simulate the variable width of riparian vegetation buffer under different planning scenarios,to satisfy the simulation of riparian vegetation buffer width at different site.(2) Based on the topographic map of Chongming Island to generate the gradient data,based on the color infrared remote sensing image to generate the Manning's Coefficient,based on the model of soil hydraulic properties to generate the saturated hydraulic conductivity and the soil moisture storage capacity,could establish a comprehensive spatial database of riparian vegetation buffer which could effective support the calculation and simulation of riparian vegetation buffer width.(3) The total length of the riparian vegetation buffer in Chongming Island is 952.26km,the total area is 9.48 km~2 and the construction ratio of it achieves above 80%.The riparian vegetation buffers are mostly narrow and the average width is only 9.96m,which causes negative effect on protecting biological diversity.The riparian vegetation buffers are scarce in Chongming Island and their overall density is 0.75km/km~2.(4) Taking the south and north horizontal river in Chongming Island as an example, under present status 1 which the decontamination efficiency ratio of riparian vegetation buffer is 1 and the major vegetation composition is a forest,based on detention time model,simulate the south and north horizontal river riparian vegetation buffer in Chongming Island.The width changes in the range of 3m～21m,among them,the width of the main districts in between 6m to 12m.Based on the hydraulic model,the width of the south and north horizontal river riparian vegetation buffer in Chongming Island changes in range of 6m～33m,among them,the width of the main districts in between 9m to 15m.Integrating the simulation results of detention time model and the hydraulic model shows that the width changes in range of 6m～33m, among them the width of the main districts in between 9m to 15m.(5) Under present status 2,which the decontamination efficiency ratio of riparian vegetation buffer is 1 and the major vegetation composition is a grassland,the detention time model simulating the south and north horizontal river riparian vegetation buffer in Chongming Island shows that the width changes in the range of 3m～33m,among them,the width of the main districts in between 6m to 15m.Based on the hydraulic model,the width of the south and north horizontal river riparian vegetation buffer in Chongming Island changes in range of 6m～42m,among them, the width of the main districts in between 12m to 21m.Integrating the simulation results of detention time model and the hydraulic model shows that the width changes in range of 6m～42m,among the width of the main districts between 12m to 21m.(6) Under present status 3,which the decontamination efficiency ratio of riparian vegetation buffer is 1 and the major vegetation composition is a landcover present status,the detention time model simulating the south and north horizontal river riparian vegetation buffer in Chongming Island shows that the width changes in the range of 6m～39m,among them,the width of the main districts in between 9m to 21m.Based on the hydraulic model,the width of the south and north horizontal river riparian vegetation buffer in Chongming Island changes in range of 6m～48m,among them,the width of the main districts in between 12m to 24m.Integrating the simulation results of detention time model the hydraulic model shows that the width changes in range of 6m～48m,among them the width of the main districts in between 12m to 24m.(7) Comparing the simulation results of riparian vegetation buffer with the landscape pattern characteristics present status of the south and north horizontal in Chongming Island shows that under the planning scenario 1,required to build riparian vegetation buffer 0.84km~2,under the planning scenario 2 required to build riparian vegetation buffer 1.80km~2,and under the planning scenario 3 required to build riparian vegetation buffer 2.20km~2.For the present status of the south and north horizontal riparian vegetation buffer in Chongming Island which can not meet their ecosystem services functions,should integrate the different planning scenarios of simulation results,increasing the construction,appropriate to broaden the riparian vegetation buffer.If the riparian vegetation buffer present status is slightly broader than the simulation results under different planning scenarios,it can be a combination of the surrounding land use,landscape pattern and the site condition of riparian zone for an appropriate development and utilization,to ensure that the demand of the construction in cities and towns surrounding land resources of riparian zone.
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