Effects of topography on status and changes in land-cover patterns, Chongqing City, China

Chongqing Municipality, located on the upper reaches of the Yangtze River, is one of China’s four largest megacities, comparable with Shanghai, Beijing, and Tianjin. In recent years, Chongqing and its surroundings have been experiencing severe environmental problems, such as urbanization, pollution, and deforestation, due to the rapid economic development of China’s inland region. Understanding the current land-cover status over a wide scale, as well as changes in land-cover over time, are necessary for improving the urban environment and implementing conservation measures in the Chongqing region. In this study, remote-sensing data from 1993 and 2001 were used to analyze land-cover changes. Due to the distinctive mountainous topography of Chongqing, digital topography data shuttle radar topography mission (SRTM)-3 were also used. The results of the analysis showed that urban area increased from 109.91 km² (5.7%) in 1993 to 166.84 km² (8.7%) in 2001. This increase came at the expense of agricultural and vegetated areas. Although irrigated paddy field and dry farm land decreased due to the development, these two land-cover categories still covered the largest agricultural area. Correlating the land-cover changes with different topography types, the results showed that forest covered a larger area and enjoyed a higher frequency of distribution at higher elevations and on steeper slopes. The increase in urban area, in contrast, was apparently associated with lower elevations and milder slopes. These results indicate that incorporating terrain characteristics into remote-sensing analysis can be a useful tool in developing conservation measures for vegetated and agricultural areas.