[Presentation]Using remote sensing to assess the damage mitigation effect of coastal forest in Sanriku coast and classification of the damage of coastal forest caused by the 2011 Tohoku Tsunami

Abstract:
Japan is an island nation surrounded by oceans. In order to protect inland area from coastal disasters caused by sea breezes, sand blow, high tides, and tsunamis, coastal forests are developed in large area. In Tohoku Region, a large area of coastal forests are suffered the great damage by 2011 Tohoku Tsunami. The purpose of the study is to assess the damage on coastal forest in Sanriku coast by using remote sensing with satellite images and aerial images and to assess the damage mitigation effect of coastal forest by using spatial analysis. The research method consists of a remote sensing method and a spatial analysis with DEM, polygon data of damaged building and field survey. The remote sensing analysis shows distribution and are of the classified damage on coastal forest by the comparison of NDVI between Pre- and Post- Tsunami satellite images followed by the detection of pixel change between Pre- and Post- Tsunami aerial images. By using GIS data, coastal forests in Sanriku coast are classified into expected damage mitigation effects by height, width, direction of shores, and distance from coastline. Damage mitigation effect of each coastal forests with classes are evaluated by analysis with data of building damage and tsunami reached line.

Abstract(Japanese):
四方を海に囲まれた日本の海岸では，海からの潮風・飛砂・高潮などによる災害から内陸部を守るため広い地域で人工の海岸林が造成されている．東北地方三陸海岸の海岸林は2011年3月11日に起きた東北地方太平洋沖地震の津波によって広範囲にわたって流出・倒伏した．本研究では海岸林の被害の把握と津波被害軽減効果の評価を目的とする．衛星画像と航空写真を元に，海岸林を被害の規模，樹木の倒伏方向，地形や海岸の向きなどで分類し，被害の実態を調査する．その後海岸からの津波の到達距離や付近の建築物の被害状況を分析することで津波被害軽減効果の評価を行う．以上により，海岸林の津波被害軽減の実績と海岸林そのものが受けた被害が明らかになることにより，期待される津波被害軽減効果の高さや造成の緊急性などの優先度を示すことができ，今後の防潮林政策における海岸林造成プロセスへの貢献が期待される．
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