Assessing the impact of storm surge flooding on coastal pine forests using a vegetation index

For the sustainable management of coastal pine forests as green infrastructure, the condition of coastal pine forests, including the effects of storm surge flooding, must be assessed, and the resulting information should be presented to the management entity. Low-altitude remote sensing (LARS) using vegetation indices is considered to be an effective tool for the rapid assessment of the condition of coastal pine forests. This study aims to demonstrate that the normalized difference vegetation index (NDVI) can be used to assess changes in the condition of coastal pine forests following a storm surge flooding through the analysis of the relationship between the NDVI calculated by LARS and the condition of trees surveyed in the field. The study site was a coastal pine forest in Osato Matsubara, Kaiyo Town, Tokushima Prefecture, Japan. In this forest, a lot of the trees died due to a storm surge flooding caused by a typhoon in October 2019. Trees within the study area were surveyed to assess their vitality. Vegetation indices were calculated by LARS. In the area without storm surge flooding, 90% of the trees had a vitality level of 5 (healthy), whereas in the area with storm surge flooding, 67% had a vitality level of 1 (completely dead). The NDVI was low in the area with storm surge flooding, indicating that tree mortality due to storm surge flooding can be evaluated by NDVI.