STUDY ON THE EVALUATION OF TSUNAMI REDUCING BY COASTAL CONTROL FOREST FOR ACTUAL CONDITIONS

摘要

The field survey and the literature study on the control forest conditions are carried outrnto evaluate the effect of actual coastal forest and to find the condition of coastal forest.rnThe relation between the forest density and the diameter of trunks is obtained throughrnthe measurement of control forests and some previous researches, which can be usefulrninformation for the evaluation of effects. The numerical simulation including thernmodel of control forest is performed for evaluating the quantitative effect for tsunamirnreduction and damage. The table to estimate the reduction effect in terms of wavernheight, velocity and hydraulic pressure is obtained and can be compared the Shuto’srntsunami damage criteria. Finally, the literature study was done to recognize thernmitigation effect of tsunami disaster by the coastal forest in the past. Four mainrnfunctions to reduce tsunami disaster are found; 1) to stop drifts or ships carried by arntsunami, 2) to reduce tsunami energy, 3) to form sand dune protecting tsunamis as wellrnas high waves, and 4) to catch people carried back by a tsunami to the sea. However, itrnshould be reminded that the coastal forests would be destroyed by a huge tsunami andrnwould be floating material to cause secondary damage.