Relationship between treefall damage and forest structure of Pinus thunbergii coastal forest by the 2011 Tohoku earthquake tsunami disaster

- An example of Misawa City of Aomori Prefecture -

Abstract

The Pinus thunbergii coastal forest in Misawa, Aomori Prefecture, Japan, was partially damaged by the 2011 Tohoku Earthquake tsunami. The forest extended 110-370 m from the beach, and the tsunami reached a residential area 440 m from the beach. The height of the tsunami was 7.4 m above the beach. Trees within 200 m of the beach were felled by the tsunami. The inundation depth of the tsunami was 4.2 and 1.8 m at 150 and 370 m from the beach, respectively. Tree size, crown height and forest age increased from the sea inland. The mean diameter at breast height (DBH), mean height, mean crown height, and forest age of the forest stand 180 m from the beach were smaller than those of the forest stand 212 m from the beach. The density of stems in the forest stand at 180 m was greater than that at 212 m. In conclusion, the increase in DBH caused by self-thinning with aging is important for tsunami resistance. From a management perspective, increasing diameter growth by thinning is important.