Change detection of landslides and debris in south Taiwan after “Morakot” typhoon based on HJ-1-B Satellite images

The 0908 typhoon “Morakot” heavily attacked Taiwan. It brought strong rainfall which not only caused water level rise in several reservoirs and rivers, but also triggered a large number of landslides, debris flow, collapse and other geological disasters. In this paper, using NDVI(Normal Differential Vegetation Index) subtractive method, together with band combination symbol coding method, “Morakot” induced changes in south Taiwan were fast detected based on HJ-1-B (Environment and Disaster Monitoring Satellites Constellation 1) remote sensing data. The areas where geological disasters and hydrology (including reservoirs and rivers) changes occurred were extracted, and then the results were analyzed quantitatively. The results showed that NDVI subtractive method could well detect the quantities and size of landslides and debris, as well as enlarged area of reservoirs and rivers, and proves to be a fast and effective approach for the monitoring and assessment of typhoon-induced changes.