Vegetation recovery monitoring and assessment at landslides caused by earthquake in Central Taiwan

Massive landslides, caused by the catastrophic Chi-Chi earthquake in 1999, occurred at the Jou-Jou Mountain area in the Wu-Chi basin, Taiwan. Multi-temporal satellite images and digital elevation models coupled with GIS were used to process the vegetation index analysis for identifying landslide sites and calculating the vegetation recovery rate (VRR). Topographic information for these areas was extracted. Eight hundred twenty-nine hectares of landslide area was extracted from multi-date NDVI images by combining the image differencing method with the change detection threshold. Over 2 years of monitoring and assessing, the vegetation recovery rate reached 58.93% original vegetation regeneration in the landslide areas. Soil moisture is one of the most important environmental factors for vegetation recovery in the landslide sites. The analyzed results provide very useful information for decision making and policy planning in the landslide area.