The Study Of Multi-scale Analysis In Urban River Accessibility Evaluation

The Yangtze River delta belongs to plain river network; it is a dense river system and is rich in water resources. However, in a period of fast city development, more and more river is faced of human occupation, landfill, straightening, hardening and canalization. Riparian zone become narrow or even disappear, and it becomes more and more artificialized. In addition, the construction of buildings along the river and the water conservancy facilities block the path for citizens to touch the water. These human affect which make a profound impact on river lower the accessibility and hydrophilic of river. This paper attempt to evaluate the accessibility of city-level and district-level rivers in Shanghai from three scale. The main work and conclusions are:(1) Summarize the concept, features and factors of influence through retrospective studies of works at home and abroad. Now most researchers define accessibility as the convenience of individual reach a destination through a kind of transportation. The features of accessibility are spatiality, timeliness and socio-economic value. The influence factors of accessibility are the choice of transport mode, variation distance and personal evaluation. Summarize the method of accessibility evaluation in the past and compare the merit and demerit. The method of accessibility evaluation can be divided into qualitative evaluation and quantitative evaluation. The quantitative evaluation holds dominant position, and the method of ArcGIS is the main method of quantitative evaluation. According to the method and principle of ArcGIS evaluation, the method can be classified into buffer zone evaluation, cost distance evaluation and gravitational energy evaluation. Among these methods, gravitational energy evaluation is more comprehensive, it takes the interaction of river and citizens into account. However, the modeling and calculating of it is complex, and it is not easy to promote. In this paper, the two-step mobile search method is taken to evaluate the accessibility of river in Shanghai and it is a better method of accessibility evaluation.(2) Take the shortest distance method, cost distance method and two-step mobile search method to evaluate the accessibility of city-level and district-level rivers in Shanghai.The conclusion of the study show:①In the conclusion of three evaluation method, the accessibility of rivers in Shanghai presents a trend of inside high and outside low. ② However, according to the data of accessibility level percentage, the high accessibility area of shortest distance method and cost distance method is higher than 40%. ③The result of two-step mobile search method shows the percentage of high accessibility area holds up to 10.36%, and it conform to the physical truth of accessibility in Shanghai. So two-step mobile search method is the suitable way to evaluate the accessibility of rivers in Shanghai.(3) According to field research, use the two-step mobile search method to evaluate the accessibility of city-level and district-level river in central city of Shanghai. The results show:①According to the features of river bank, classify the river accessibility into three kinds, impeditive accessibility, unimpeded accessibility and hydrophilic accessibility. Among these three kinds, impeditive accessibility takes the highest percentage; hydrophilic accessibility takes the lowest percentage. The result shows the accessibility of rivers in central city of Shanghai is also at low level.②Take two-step mobile search method to evaluate the accessibility of central city of Shanghai, the result shows that the accessibility of rivers presents a trend of inside low and outside high. The high accessibility area holds up a percentage of 16.45%, although it is a bit higher than the level of river in Shanghai, but it is still at a low stage.③ To the river of impeditive accessibility, the high accessibility area is centered on the upstream of Suzhou River. In addition, the north of Yangpu district and the south of Xuhui district also present high accessibility. To the unimpeded accessibility river, the high accessibility area is centered on the downstream of Suzhou River. In addition, the east of Yangpu district also presents high accessibility. To the hydrophilic accessibility river, the high accessibility area is centered on the upstream of Suzhou River and Yangtze River.④In the calculating of river accessibility, the accessibility of river in central city of Shanghai is higher than the accessibility classified river.(4) According to field research and interviews with local people, Suzhou River is divided into 15 sections to evaluate the accessibility. The results show:① According to the result of two-step mobile search method, the accessibility of Suzhou River is higher than the accessibility of all rivers in Shanghai. And it presents a trend of west high and east low. The accessibility of upstream of Suzhou River is high, and the accessibility of downstream is low.②The results of accessibility evaluation of north and south sides shows the difference was insignificant. But the accessibility of north side is a bit higher than the south side.③The impeditive accessibility river tends to high in the west and low in the east. The unimpeded accessibility river tends to high in the east and low in the west. The hydrophilic accessibility river is dispersed; only take a high area in the upstream.④ The highest accessibility river in the classification is unimpeded accessibility river, the accessibility level of impeditive accessibility river and hydrophilic accessibility river is still in a low stage.This thesis is supported by National Natural Science Foundation of China (71037055), the study of regulation and management of yangtze river delta based on river health.