Study On Ecological Environment Impact Assessment Method For Expressway In Ecologically Fragile Areas

The alpine region of Qinghai Province is one of the main ecologically fragile areas in China because of its harsh natural conditions and weak self-regulation ability of the ecosystem.The construction and development of expressway in this region would inevitably cause certain interference to the ecological environment of the road area.The assessment of eco-environmental impacts of road area in high-altitude ecologically fragile areas has become a hot topic in current studies.However,the existing studies lacked a systematic study on the screening methods of ecological indicators.There were various problems in the assessment system,such as diverse indicators,different standards,and Insufficient applicability of the quantitative models.The method of RS and GIS spatial analysis and geostatistical analysis supplemented by field investigation was used in this paper.On the basis of the on-the-spot investigation on the eco-environmental of the typical expressway in Qinghai Province,the comprehensive analysis indicators screening method was adopted.Firstly,by drawing lessons from the domestic and international research results of the eco-environmental assessment and the practical working experience of experts,the eco-environmental assessment indicators library of expressways was constructed from two perspectives: the inherent vulnerability of eco-environmental caused by natural conditions and the external vulnerability of eco-environmental caused by human disturbance.Seven extremely important indicators for road eco-environment assessment were screened out based on the aggregation method and hierarchical clustering analysis method.Subsequently,Landsat OLI/TIRS satellite remote sensing images and GDEM V2 digital elevation data were used to extract the data information of these indicators,and the ecological indicators containing repetitive information were quantitatively eliminated by contribution index cyclic analysis method.This method guaranteed that the ecological indicators in the assessment model were "few and precise" from qualitative analysis and quantitative analysis.Aiming at the problems in traditional comprehensive index assessment method,such as the fuzziness and uncertainty when the indicators were dimensionless and the dependence on expert knowledge when the weights were determined,a method of regional assessment based on multiple linear regression was proposed.This method determined the weights of ecological indicators by the least square method to establish an eco-environment assessment model in ecologically fragile areas.Then,the explanatory ability of the model was verified and analyzed from the two aspects of the rationality of the selected ecological indicators and the reliability of the model.Finally,the model was applied to the study of the environmental impact model of different ecosystems in the expressway area.The results showed that the expressway construction and operation was the first driving force for the eco-environment changes in ecologically fragile areas.The spatial extent and the degree of expressway on the ecological environment changes in different ecosystems were diverse due to various eco-environment backgrounds.150 m on both sides of the expressway middle line should be regarded as the key regions for ecological environment protection in ecologically fragile areas.This paper had theoretical significance for the screening method of evaluation indicators and the assessment method of expressway eco-environment impact,and the results had practical value for ecological risk early warning and environmental protection of expressway in ecologically fragile areas.