Temporal-spatial growth pattern and driving forces of urban expansion in Xi'an over past 30 years

Abstract

The construction pace of the Middle-West urban agglomeration has greatly accelerated with the implementation of the "One Belt One Road" initiative and the new urbanization construction strategy. Adhering to the green concept of "intensive, energy saving, ecological development" and implementing a "people-oriented view" as core value have become the new trends. To understand the process of urban temporal-spatial growth pattern and driving forces, the urban spatial patterns at seven periods (1985, 1990, 1995, 2000, 2005, 2010, 2015) in Xi'an (the starting point of Silk Road) were extracted from multi-temporal Landsat satellite remote sensing data gathered in the past 30 years. Moreover, the quantitative and geometric characteristics of urban expansion were analyzed using the Urban Expansion Intensity Index (UEII), Urban Expansion Rate Index (UERI), and Compact Degree (CD). We analyzed the driving forces of urban expansion in Xi'an city from five aspects, such as population, Gross Domestic Product (GDP), macro policy (such as the integration of Xi'an and Xianyang), and traffic conditions. These measures were analyzed using social and economic statistical data in the same period. The results show the following. (1) Urban coverage increased from 107.44 km2 to 724.19 km2, which shows an expansion of 6.74 times. The annual average expansion area in the past 30 years was approximately 20.56 km2. UEII and UERI displayed a growth tendency after initial declines, simultaneously reaching the summit from 2005 to 2010. (2) The urban spatial pattern mainly expanded to the east, north, and northwest districts from 1985 to 2000. However, the trend moved to the west, south, and southwest areas in the next 15 years. Meanwhile, CD showed a rapid decrease of 0.367 to 0.262 from 1985 to 2000 and then slowly declined by 0.07 since 2000. (3) The urban area presented two power relations with GDP and displayed a linear positive correlation with population. Finally, government policy, such as the integration of Xi'an and Xian Yang, can influence the urban macro structure, scale of expansion and development, road traffic, and infrastructuresupporting construction. As a Middle-West China megacity, Xi'an plays a leading role in the new urbanization construction strategy. However, urban development faces problems, such as rapid population growth, insufficient water resources, and fragile ecological environment. Therefore, we suggest that the government take the "green, ecological, low-carbon" sustainable development path, improve the planning of ecological function areas, accelerate the construction of ecological barriers, reasonably allocate water resources, and develop competitive industries.