Research Urban Expansion Characteristics Of Wen Jiang And Its Intensive Utilization Of Construction Land In Chengdu

Urbanization would remain an inevitable trend for many small-medium cities in China for a long period of time in the future. In the meanwhile, they would also face dual pressure of urban expansion and intensive utilization of land. In order to ensure city development without wasting land resources, researches on the intensive land utilization degree were conducted under the state of urgent need for urban expansion.Mature development of remote sensing technology makes multi-cycle and high-resolution spatial data resources important method for the study of spatial and temporal variations of urban scale. This paper studied the spatial and temporal variations of built-up areas in Wenjiang. District by extracting data of six phases of the built-up areas based on remote sensing images of the six phases in 1984、1996、2002、2012 applying supervised classification in combination of computer interpretation. We also conducted research on the intensive land utilization level in Wenjiang District among 2002 to 2012,by selecting 11 indexes from Land use intensity, increase consumption index, land elasticity index and contribution index applying Delphi expert scoring method, analytic hierarchy process (ahp) and multi-factor comprehensive evaluation method based on statistics of Wenjiang District. Traditional statistical analysis method was adopted to study the main natural, social and economic factors that affect urban expansion and intensive utilization of land for construction. On this basis, the extent of impact on intensive land utilization was also studied adopting Grey correlation analysis method. Main findings are as follows:(1) Growth of built-up areas in Wenjiang district is significantly accelerated during the studied period. From 1984 to 2012,the built-up areas increased by 78.51km2 with an annual expansion of 2.80 km2;from 1984 to 1996, the annual expansion rate is 1.14 km2/year, and the annual expansion intensity is 5.06%; from 1996 to 2002, the built-up areas increased 18.21 km2, with an annual expansion of 3.04 km2/year, and an annual expansion intensity of 8.37%; From 2002 to 2012, the annual expansion rate is 4.66 km2/year, and the annual expansion intensity is 8.55%.(2) The spatial form of construction land in Wenjiang has an obvious change during the studied period. The compactness index level is lower than 1 throughout the studied period. The changing trend from 0.63 in 1984 to 0.36 in 2012 indicated an increasing space discrete degree of Wenjiang city form. Fractal dimension index increased from 1.22 in 1984 to 1.38 in 2012. With an approximately 1 fractal dimension index showed a relatively simple urban space form. The built-up areas were expanded mainly by export-oriented expansion, and internal filling expansion was also strengthened at the same time. Seen from city center coordinates and centroid coordinate mobility, the city center slowly moved toward southwest and will still remain the trend in the future.(3) With the expansion of built-up areas, the intensive utilization of land showed a trend of continuous increase followed by decrease then increase again. Through the establishment of evaluation index system on construction land intensive utilization adopting Delphi method, analytic hierarchy method and multi-factor comprehensive evaluation method, we know that the construction land utilization was increased from 36.02% in 2002 to 59.21% in 2005; and 40.96% in 2006 to 83.28% in 2012.(4) Based on natural, social and economic factor analysis, grey relational analysis was further adopted to evaluate the impact factor on city expansion and intensive land utilization. The results indicated that Topography, rivers, climate, population growth, regional gross domestic product (GDP), fixed investments, the urban population, the number of secondary and tertiary industries laborer, the secondary and tertiary industry output value, total population, urban and rural residents per capita income, accessibility of traffic, policy system, urban planning, arable land scarcity, the urbanization rate and grain yield level, all had different impact on city expansion and intensive land utilization. To be the most important factors, the correlation of population, the secondary and tertiary industry and food security levels with construction land scale reached above 0.9; as a medium factor, the correlation of GDP and land scale is 0.8, and as a less important factor, the correlation of fixed investments and land scale is 0.56.