Recovery of communities affected by debris flows and estimation of the mental damage to the costs of victims

Yuji YASUDA, Yoshimasa MORI and Nobuaki KATO

A debris flow disaster can cause considerable damage in the stricken area, which can affect the people dwelling there. We investigated changes in communities each year after a disaster. We also proposed a method for calculating the monetary cost of living as a refugee, which causes long]lasting mental trauma. The results were as follows:(1) after a debris flow disaster, the community does not recover to its original situation, and people are forced to out]migrate to neighboring regions or public housing, as per the examples of Harihara, in Kagoshima Prefecture, and Minamata, in Kumamoto Prefecture, Japan. It became apparent that it is difficult for single elderly persons to rebuild residential housing;(2) the recovery period from a debris flow disaster in the Minamata area was estimated to be around 10years;(3) when the method was applied to a sediment]related disaster hazard area in Aso, in Kumamoto Prefecture, the total cost of mental damage was estimated to be 221.2 million yen; and (4) when the method was applied to the entire basin, which contains 68 streams that pose a danger of mud and debris flows, the monetary cost of living as a refugee, and the cost]benefit ratio of the long]lasting mental trauma, increased by 0.1.