Effect Of Large-scale Water Areas On The Structure Of Urban Street Networks

With rapid urbanization,urban street networks have been continuing to expand.Largescale water areas,as important factors that affect and restrict the street network structures and urban patterns,play a vital role in the emergence and development of cities.This thesis studies the local adaptability of urban street networks against large-scale water areas,and explores the impact of large-scale water areas on the global performance of street networks.Also,this thesis proposes and validates an evolution model of urban street networks based on the above analysis.This thesis first constructs the database of urban street networks and large-scale water areas required for this research,it takes 67 cities with large-scale water areas in China as the research objects and 25 non-water area cities as the reference objects.Then,three metrics have been proposed to quantify the geographical barrier levels considering the geographical layout,size,shape and other factors of water areas.After that,this thesis analyzes the influence of water areas on local street networks from the perspective of the orientation of local street segments.In addition,from the perspective of efficiency,accessibility and betweenness,this thesis also analyzes the influence of water areas on the global performance of urban street networks.Finally,based on the above outcomes,an evolution model of urban street networks under large-scale water areas is proposed and verified.Main conclusions include:(1)From a local perspective,when the distance from water areas to the city center increases,the distance from water areas to the nearest street segments gradually increases.Meanwhile,the water areas affect the orientation of the nearby streets.For local street networks from 100 meters to 200 meters away from water areas,more than90% of them are nearly parallel or perpendicular to the nearest water areas boundary.This influence can be ignored for local street networks 1.6km away from the water areas boundary.(2)From a global perspective,the influence of water areas is still significant in some cities with population under 2.5 Million.The correlation between the geographical barrier level of water areas and the average distance-based and time-based accessibility is only 0.089 and 0.045 respectively.The maximum betweenness of street components in cities with water areas are much bigger than those for non-water area cities,indicating that cities with large-scale water areas are more likely to be congested and more vulnerable.(3)An evolution model of urban street networks is proposed and can well reproduce the structural and geographical characteristics of real urban street networks with large-scale water areas.The results and the proposed methods can provide a theoretical support for street network planning and decision making on the construction of bridges and tunnels in cities with water areas.