This research aims to analyze the damage of coastal forests in the Pacific coast of the Tohoku region (Ofunato city in Iwate prefecture, Natori city in Miyagi prefecture and Minamisoma city in Fukushima prefecture) affected by tsunami of the Great East Japan Earthquake occurred on March 11, 2011. In order to clarify the actual situation of coastal forests, literature survey and interview survey were conducted. Furthermore, by using the geospatial information, we verified the geographical factors of disaster, such as forest conditions and topography, forest position from shoreline, the relationship between the tide breakwater and the tsunami inundation and the forest damage by the tsunami. As a result, it was revealed that topographical situations greatly influenced the tsunami flooding, and structures such as the tide wall could affect on suppression of flood expansion and damage to the forest. On the other hand, it was found that undulations such as the embankment along the coast were able to have an adverse effect on the drainage after the flood. In the future, it is considered that utilization of aerial photographs and foundation map information will be effective for visualizing and clarifying the actual situation of wide area affected by a disaster.

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クロマツ海岸林の植栽本数の決め方について文献調査を行った．植栽本数を決めるにあたって考慮すべき諸条件は示されているが，諸条件に基づいて植栽本数を決める具体的な手順は示されてこなかった．一般的とされる植栽本数10,000 本/ha は，理論的に決められたというより，諸戸（1921）の著した教科書の数値が実践の中で引き継がれてきたものと考えられる．改めて，植栽本数の決め方を次のように提案した．クロマツの生育には密植するほど有利だが，労力と経費の点から，現実的な上限を10,000 本/ha とする．最少の植栽本数の目安は，期待する樹高に達したときに林冠が閉鎖する立木密度である．活着後も防風工による植栽木の保護が必要になるような海風環境の厳しい植栽地では，樹高が保護工の高さに達したときに林冠が閉鎖する立木密度以上の植栽本数にする．なお，この立木密度は，保護工の高さが1 m の場合には10,000 本/ha になる．

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