The spatial-temporal changes of the land use/cover in the middle yangtze plain

The middle Yangtze plain, located on the central of China, is well known to the world as one of the regions mostly suffering from flooding disaster in China in recently. The increasing flooding is not only the results of the nature process, but also the results of the land use/cover change. The research on the land use/cover change is very helpful to trace the flooding damage. In this paper, a series of land use/cover coverage were first generated through visually interpreting LandsatTM and ETM image data of 1990, 1995 and 2000 with MGE and ARC/INFO software. Then, based on the net-change analysis, conversion matrix and dynamic degree model, the characteristics of spatial-temporal change and the transfer of land use/cover were analyzed in this area. The results showed that the areas of farmland and woodland decreased, while that of built-up area, water area, grassland and non-used land increased during the past 10 years, and there was a significant shifting from farmland to water body or built-up area. From 1990 to 2000, the cultivated land decreased by 78600 hm2, of which 55% was changed to water area, especially most to fishpond, and 33.41% to the built-up land. For the same 5-year interval, the pace of land-use change in 1990-1995 was much faster than in 1995-2000. By using the dynamic degree model, it was found that the greatest changes of land use/cover occurred in big city, i.e., Wuhan City, Nanchang City, and the slowest change mainly in the counties near the Dongting Lake and the Poyang Lake. Because the large-scale land reclamation from lake ever in history has been curbed effectively in this flooding plain since 1990, the authors deduced that the worsened flooding risk in this area should be attributed to the over-reclamation before 1990. Since 1990, although there has been the return of the cultivated land to lake, it has not sufficiently alleviated the flooding disaster due to a limited restore of water body.