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| Vegetation damage assessment of Beichuan County after the earthquake in May 2008 Based on NDVI |
| （1.Key Lab. of Soil & Water Conservation and Desertification Combating of the Ministry of Education, Beijing Forestry University, 100083, Beijing, China；2.Research Institute of Forest Resource Information Techniques, Chinese Academy of Forestry, 100091, Beijing, China；3. Beichuan County Forestry Bureau of Sichuan Province, 622750,Beichuan, Sichuan, China） |
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Abstract This study selected two phases remote sensing images before and after Wenchuan Earthquake on May 12th, 2008 in Beichuan County. The two images before and after the earthquake was obtained to extract vegetation covering information using normalization difference vegetation index(NDVI),and NDVI was used to estimate vegetation coverage. Then the damage degree index (DDI) of the vegetation was defined, indicating the difference of the normalized difference vegetation index before and after earthquake. The results showed that: 1) 103 landslides, 122 collapses and 10 mudslides were interpreted from Formosat-2 image taken after Wenchuan Earthquake, and the area of disaster was 17.5km2.The area of medium vegetation coverage status was 85% before the earthquake, and it reduced by 8.01km2 after the earthquake, which accounted for 45.77% of the whole area of disaster. 2) The vegetation damage was relative less serious in landslides regions, where moderate and severe damage vegetation occupied 68.66% of the whole area. The vegetation damage was modest in collapses regions, where moderate and severe damage vegetation occupied 88.15% of the whole area. Most vegetation damage occurred in mudslides regions, where moderate and severe damage vegetation occupied 99.74% of the whole area. 3) The vegetation damage was closely related to the elevation and slope grade, which was prone to occur at the elevation of 611-1543m and slope grade of 25°-45°regions. The vegetation damage was worse, most of which were severe damage with a decreasing trend along with elevation and slope grade increasing, but weakly related to the aspect factor.
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Received: 11 March 2013
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