INVESTIGATING THE POSIBILITY OF MONITORING THE RECOVERY OF TSUNAMI DAMAGES PADDY FIELDS USING MODIS 16 DAYS COMPOSITE NDVI

摘要

On March 11, 2011, the magnitude 9.0 earthquake struck Tohoku Area of Japan. At that time, a large-scale tsunami associated with the earthquake hit the large area along the coast of Tohoku Area including many paddy fields. In the previous study, the authors have investigated the possibility of using MODIS 16 days composite NDVI for monitoring the recovery condition of the tsunami damaged paddy fields. The authors have selected a number of test sites for normal paddy fields, inundated inshore paddy fields, and inundated inland paddy fields. Usually, the NDVI of typical paddy field gradually increase from May to August and suddenly decreases in September to October due to harvesting. However, in the damaged paddy fields, the NDVI did not increase much. However, once the paddy fields are recovered, the seasonal NDVI pattern became almost the same as that of normal paddy field. The results well matched with the paddy recovery report provided from the local government. However, the 16 days composite NDVI often showed abnormally low values mainly due to snow and clouds. These abnormal data make it difficult to identify the recovery condition of the paddy fields. The authors have examined the ways to identify the abnormal NDVI values and interpolated them with the NDVI of before and after the event. The result suggested that the abnormal values are well removed without removing the reduction pattern affected by the tsunami.