Research On The Expressway Accessibility And Land-use And Land-cover Change In Beijng-Tianjin-Hebei Region

Beijing-Tianjin-Hebei Region is one of the most comprehensive strength and densest urban distribution in China. Expressway has been the main traffic mode in this region due to its characteristics of high efficiency, flexibility and so on. so the accessibility index is used, which has practical significance in evaluating expressway network development. Land types change greatly in Beijing-Tianjin-Hebei Region with economic development and urbanization, the study on spatial and temporal distribution of land types and impacts of expressway on land types has important significance for integrating and promoting regional development.In this paper, expressway accessibility and land-use and land-cover change is being discussed in the period of2000to2013with the study range about all of13administrative divisions in the Beijing-Tianjin-Hebei Region which contain of Beijing. Tianjin and Beijing. Tianjin. Zhangjiakou, Chengde, Qinhuangdao, Tangshan, Langfang, Baoding. Cangzhou. Hengshui, Shijiazhuang. Xingtai and Handan.The shortest time and weighted time index are used to evaluate regional accessibility based on the method of shortest path and the expressway network data in Beijing-Tianjin-Hebei Region which is extracted by GIS.Results show the accessibility of each city generally improve, but the leverl of improvement is uneven. The accessibility arrangement decreases gradually on all sides with Beijing-Tianjin-Hebei as a center. The relative accessibility coefficient based on shortest time is more decentralized than that based on weighted time, and the relative accessibility coefficient of central and southern cities is reduced when considering the regional population.Land-use and land-cover datas are extracted from all of34TM images in2000and2013which must cover the entire study range by RS image processing technology. The analysis of land types changes in the entire region and buffer zones by GIS shows vegetation and build-up land changes significantly, and large parts of vegetation land is converted into build-up land. The area of wetland has a small proportion and decreases gradually. The increasing proportion of other land area can partly reflect the impact of human activity on nature. Due to the influence of expressway networks, change rates of vegetation, build-up land and wetland in buffer zones are faster than those in the entire region. The transfer of land type in buffer zones is more intensive and frequent when compared with that of the entire region, and the degree of disturbance is severer too. The degree of decentralization and fragmentation of vegetation and other land in buffer zones is enhanced, and the aggregation extent of build-up land is enhanced when compared with that of the entire region.