Use of Landsat TM satellite surveillance data to measure the impact of the 1998 flood on snail intermediate host dispersal in the lower Yangtze River Basin

ZHOU Xiaonong¹, LIN Dandan², YANG Huiming³, CHEN Honggen², SUN Leping¹, YANG Guojing¹, HONG Qingbia¹, Leslie BROWN⁴ and JB MALONE^4
1 Jiangsu Institute of Parasitic Diseases, Wuxi, PR China
² JiangxiInstitute of Parasitic Diseases, Nanchuang, PR China
³ Nanjing Hospital for Schistosomiasis Control, Nanjing, PR China
⁴ School of Veterinary Medicine, Louisiana State University, LA, USA

To assess the impact of the 1998 flood on snail distribution in the lower Yangtze River basin, two study areas were selected, one in the Poyang Lake region, and the other along the Yangtze River in Jiangsu province. Using image analysis software, geocoded Landsat TM data were used to create TNDVI maps based on the formula TNDVI=Sqrt [(band4-band3/band4+band3)+0.5]. The images taken in the flood season were recorded as water class and land class. The images taken during springtime were classified based on TNDVI. Composite images were created based on the time difference analysis, combining the flood season images and spring vegetation images to produce a final composite image in which potential snail habitats were identified. When compared with ground survey data collected in 2000, the corre spondence rate between potential snail habitats identified by image analysis of 1998 Landsat TM data and ground survey data in spring of 2000 was over 90% in both regions. Results indicate that ecology based methods using Landsat TM image analysis provide a new way to create snail habitat maps and predict snail distribution under specific environmental conditions associated with the extent of the annual flood season.

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created 21/12/00