Drought Risk Evaluation Using Remote Sensing and Gis : a Case Study in Lop Buri Province

Drought disasters in Thailand have been occurring with increasing frequency in recent years. A drought is one weather hazard that is often underestimated for two reasons. (i) Droughts have a slow rate of onset and, (ii) They have less visual impact on us. However, the long term outcome of a drought can be widespread and very devastating. This drought risk area evaluation study involved the intregration of Geographic Information Systems and Remote Sensing technology. JERS-1 OPS dry season data was acquired for 2 different years and was processed to detect vegetation condition change in response to drought. Physical and meteorological factors were analysed and drought risk areas were identified based on the criteria of Ministry of Science, Technology and Environment (MOSTE) of Thailand. NDVI change between a normal year (1995) and drought year (1997) was analyzed for each drought risk area. It was found that the value of the NDVI is lower in high drought risk areas, which justifies the modified criteria of MOSTE. 1.INTRODUCTION Drought disasters in Thailand have been occurring with increasing frequeency in recent years. The last droughts in Thailand occurred in the dry season several years ago, when the severest effects were seen in central, north eastern, eastern and southern regions. Lop Buri is the one province which is critically affected by drought and water shortage events. Its main land use is agriculture, the primary crop being rice, which requires a lot of water for growth. Therefore drought hazard studying in this region is important for migration and agriculture planning. This study has used remotely sensed data subject to a Normalized Difference Vegetation Index (NDVI) calculation in order to prove and support the modified criteria of drought risk areas evaluation developed by Ministry of Science, Technology and Environment (MOSTE). Evaluation of drought is one of the important items for the mitigation of its effects, but this evaluation is often difficult to obtain over large and remote areas. The Use of remote sensing and GIS is useful for drought evaluation to obtain up to date information that is difficult to collect by traditional methods such as field survey and sampling questionnaires.