Exploring Urban Expansion Using The Global Human Settlement Layer (GHSL) In The Yangtze River Delta (YRD) Metropolitan Region,China

Since the reform and opening up,China has experienced rapid urban expansion.With the acceleration of the urban expansion,a series of social-environment problems are gradually produced.In order to better grasp the dynamic characteristics of urban expansion,quantitative and qualitative analysis of urban expansion is necessary.Urban expansion analysis can also provide scientific basis for policy making and is important for the sustainable development of social and economic environment.In addition,although the urban expansion analysis is one of the hot topics in the field of resource management,there are few researches on the quantitative analysis of large-scale urban expansion using landscape metrics.Based on the above analysis,the spatiotemporal characteristics of the urban expansion process in the YRD are investigated by using the global human settlement layer(GHSL)with time-series thematic data.The development of built-up area and landscape metrics describing urban expansion are analyzed from 1975 to 2014.The analysis uses a multi-scale approach on the level of the metropolitan region as well as for 17 cities in the YRD metropolitan region.At the same time,the dynamic characteristics and classification of the urban expansion are analyzed by landscape metrics.Finally,buffer zones are built around the city center in each city to conduct a zonal-based expansion analysis.In addition,this paper also analyzes the land use planning policy and connect urban expansion with policy objectives.The results show that:(1)the urban expansion of the Yangtze river delta metropolitan region is mainly based margin expansion which is a coalescence process.(2)17 cities can be classified according to the pattern of expansion,urban morphology and structural change characteristics,and the same provinces and urban agglomerations have similar expansion characteristics.(3)The growth rate of urban built-up area is too fast,and the integration use of urban land does not match policy goals.Land policies related to urban expansion management still need strengthen for balanced,integrative development as well as intensive and economic utilization of urban land.The research results of this paper clearly reflect the dynamic characteristics of urban expansion in the Yangtze river delta metropolitan region,which can help to monitor and understand the process of urban expansion.In addition,the urban expansion and policy analysis have far-reaching significance for relevant land policies making and improvement of urban expansion monitoring and management in the Yangtze river delta metropolitan region.