Evolution of urban morphology and identification of extension direction of estuary port city

Urban morphology is an overall form of urban spatial structure as an external outline shape of urban space. Study on the evolution of urban morphology and identification of its expansion direction is related to the sustainable development of urban spatial structure. So, it has been an important research field of urban planning subject. This paper analyzed the evolution of urban morphology and identification of extension direction systematically, taking Nantong City, the typical estuary port city of the Yangtze River as an example, and three phases of distribution maps of construction lands as basic spatial data, aided by the means of GIS. Firstly, it made some basic measures by Shape Index, Extend Rate, and Fractal Models. Secondly, it adopted the theory of Convex Hull to identify the extension types. Finally, it selected the model of Urban Spatial Expansion Intensity to identify the direction preference of spatial extension. The results show that: 1) The construction of three urban districts in Nantong has essentially complied with the development laws of both new and old urban areas in recent years. 2) The urban area has extended along the Yangtze River, shown as zonal groups. It also shows a trend of diversity of the direction preferences, while following the laws of form evolution and spatial expansion of estuary port cities. 3) Further researches are needed according to the specific situations, such as the development of the location of the urban external transportation, the construction of the deep-water outer harbor etc.