Abstract
Mountainous areas in Japan has been exposed at the risk of rock-fall disaster. On the other hand, since the budget expensable for countermeasures against such disasters are limited, priority of the slopes at a risk of rock-fall should be discussed. In such situation, it is common to evaluate the priority of the site by cost-benefit-ratio and the benefit of the countermeasure is evaluated by the reduction of the expected economic loss. Much of researches however have pointed out the limitation of the evaluation only by the reduction of expected economic loss. This study formulates a mathematical programming problem to find an optimal strategies by minimising the weighted sum of the reductions of both expected economic loss reduction and the variance of the loss considering the budget constraints. We showed that the reduction of variance for each site is separable and the proposed model can be formulated as binary integer linear programming problem (BILP), if the occurrence probability of each slope is independent. The proposed model is first applied to the small network to see the performance, and then is applied to plan the optimal countermeasure planning of rock-fall disaster in Hida region of Gifu Prefecture. The result suggest the advantage of the proposed method.
