Effectiveness of the coastal forest in stopping drifts from entering the residential area

- A case study of the Pinus thunbergii coastal forest in Hachinohe City Aomori Prefecture

Abstract

The 2011 off the Pacific coast of Tohoku Earthquake Tsunami surged through the Pinus Thunbergii coastal forest of Ichikawa-cho, Hachinohe City in Aomori Prefecture with about T.P.(Tokyo Peil) +7-8 m (4 m above ground). The tsunami height in the forest was presumed to be about T.P.+7.0 m (3-4m above ground). The tsunami moved drifts such as fishing boats (20 or more) into the coastal forest. The fishing boats etc. mowed down much of the coastal forest, but were eventually stopped and did not reach the residential area to its rear. In other words, the coastal forest demonstrated a catching drift function. Conversely, the coastal forest sustained larger damage based on the scale of the tsunami than suggested by existing knowledge, which indicated the significant influence of the drift. In addition, although the width of the coastal forest was considered sufficient, it was actually insufficient depending on the direction in which the fishing boats flowed.