Assessing the impact of the 2004 tsunami on mangroves using remote sensing and GIS techniques

While tsunami characteristics and effects are not fully understood in the countries around the Indian Ocean, there are reports suggesting that mangroves, acting as a barrier, significantly reduce the devastation caused by the waves. This study proposes a creative approach to investigating the impact of the 2004 tsunami on mangrove vegetation. The approach involves a combination of Geographic Information System (GIS) proximity analyses and change detection methods in remote sensing to delineate multiple buffer distances from the coastline into four homogeneous subregions. The changes in land cover are then assessed in these subregions before and after the tsunami event. The proposed approach provides a more reliable and accurate means than conventional methods to evaluate spatial patterns of damaged areas through different land characteristics along the coastline. There are major damages to land cover, representing an average of 26.87% change, in those geographic locations with low mangrove coverage that are in close proximity to the coastline in all four subregions, whereas less damage is apparent in locations with high mangrove coverage, representing an average of only 2.77% change. The optimum distance between 1000 and 1500 m of mangrove buffer would be favourable and most effective for reducing the damage by potential tsunami waves. The findings support the need for mangrove replantation and management in the future and may serve as a prototype for studying impacts of tsunamis in other affected countries.