Using remote sensing to assess the protective role of coastal woody vegetation against tsunami waves

This paper describes how remote sensing techniques were used to study the effect of mangroves and other woody coastal vegetation as a protective measure against the 2004 Indian Ocean Tsunami. Remote sensing made it possible to compare pre‐ and post‐Tsunami images of large areas. A study site was selected based on medium resolution Landsat imagery and existing topographic maps. Selection criteria included substantial damages reported, presence of woody vegetated and non‐vegetated shorelines, homogeneous bathymetry and good coverage of pre‐ and post‐Tsunami satellite imagery. The Pichawaram mangrove, Tamil Nadu, India, matched these criteria. Pre‐ and post‐Tsunami Ikonos and QuickBird images were compared through the visual interpretation of pre‐Tsunami coastal vegetation and post‐Tsunami damage. The results were validated in the field. The analysis showed that mangrove forests and coastal shelterbelts provided protection from the Tsunami. This was concluded from analysing the spatial distribution of damage relative to woody vegetation along the coast as well as transects detailing the amount of damage behind the coastline and the coastal woody vegetation.