Modelling the Impacts of Different Policy Scenarios on Urban Growth in Lanzhou with Remote Sensing and Cellular Automata

Integration of remote sensing and CA has been the frontier edge of the urban research. This paper presents an application of remote sensing and cellular automata in modelling the impacts of different policy scenarios on urban growth in Lanzhou, China. SLEUTH urban growth model, was introduced and coupled with remote sensing loosely. SLEUTH was an extended cellular automata model, developed with predefined growth rules applied spatially to grid maps of cities, and designed to be both scaleable and universally applicable. SLEUTH is an acronym for the input layers that the model uses in gridded map form: Slope, Land Use, Exclusion, Urban Extent, Transportation and Hillshade. In this paper, the main built-up area of Lanzhou is chose as the study area, which is a typical valley-basin city. Historical data sets derive from aerial photos of 1980 (1:10000) and 2001(1:4000), and Landsat TM images collected in 1986 and 1993.And three different policy scenarios were designed to explore its different impacts on urban growth, respective to calibration and prediction of the model. The first scenario was without any consideration given to urban planning or policy; the second scenario considered urban planning and policies, but only 50% implementation of the overall plan or policies; the third scenario considered full implementation of the urban plan and polices. The calibrations of the three scenarios all reflect the restrictive land use for development in Lanzhou, and the intentions to control the sprawl strictly. The progressive urban developments are projected into the future 20 years under three different scenarios. Compared with statistic and spatial distribution under different scenarios, it can be concluded the impacts of policies on urban growth in Lanzhou are profound, and the government plays a very important role in urban growth. And the second scenario is more close to the reality, the implementation of urban planning and policies in the reality is not very good and th- - ere are still many problems about urban planning and decision-making in urban growth of Lanzhou, such as arbitrary and scientific.