Abstract
Pine trees (red and black pines) at Takata-matsubara, which is scenic coast in Rikuzen takata city (*1), were completely broken down due to logging or breaking by huge tsunami at Great East Japan Earthquake. Although just one big red pine tree was survived, it was submerged at high tide or ground water level was increased due to declining of ground level by 84 cm, inhibiting root growth and its function. sheet pile of 6 m long was driven surrounding the tree (15m×15m) to prevent the flow of ground water towards the tree from the body of sea water. However, ground water level inside the sheet pile was increased by the spout of ground water, due to quick sand phenomena, which has been known to occur when sheet pile driving was conducted at sand area in sea coast. We tried to drain water using drain pump, but could not suppress the increase of ground water level. Roots system at surface soil layer lost their vitality and died due to flooding and salt damage. Leaves were green-colored and kept their vitality in middle of March 2011, immediately after the tsunami disaster, however they became to be brown gradually and almost died in August 2011, as a result of the increase of transpiration by increasing temperature then. Thus, utilizing of sheet pile driving technique at sand area in sea coast has high risk extremely with consideration of spout of ground water due to quick sand phenomena. In such a condition, lifting root system technique using root clump for transplanting can be considered. If lifting and transplanting using heavy machine was hard to conduct, alternative methods of making slope and pulling the tree on the rollers (*2) by winch or jacking-up can be considered. Early transplantation is required because extending new roots occurs in early spring. Tsunami went through along spur, reaching to 25 m high, and cedar plantation was lost by salt damage. Precious giant cedar in the Imaizumi-Tenmangu shrine was also died by the salt damage. Here we discussed the tree damage due to flooding and salt damages to roots and effects of flooding on the sandy soil, as a result of the increase of ground water level by sheet pile driving technique at sand area in sea coast.
