Assessing rice crop damage and restoration using remote sensing in tsunami-affected areas, Japan

The tsunami that occurred on March 11, 2011, in Japan caused widespread devastation of infrastructure and rice cultivation areas. This study assessed the rice growing areas damaged due to this event and the restoration progress using moderate resolution imaging spectroradiometer data. The data were processed for 2010 to 2013, comprising four main steps: (1) data preprocessing to construct the smooth time-series enhanced vegetation index 2 data, (2) rice crop mapping using the dynamic time warping algorithm, (3) accuracy assessment, and (4) change analysis of rice cultivation areas. The mapping results validated using the ground reference data indicated overall accuracies and kappa coefficients generally >84.3% and 0.69, respectively. The results, also verified with the government's rice area statistics, reaffirmed a close correlation between these two datasets (R²>0.77). When examining changes of rice cultivation between 2010 and 2013, the rice area damaged by the tsunami during 2010 to 2011 was ~ 17,550 ha. The rice area restored after one year (2012) was ~ 6663 ha, but this regressed slightly in 2013 (5656 ha). Such information could be used by officials to better understand the tsunami-damaged rice area and the restoration progress for crop management in the study region.