A prediction of run-out distance of debris due to slope failure is the most important role in order to set up a dangerous zone for the evacuation of human damages and to plan the effective establishment measures. In this paper, the probability of run-out distance is examined through the analyze of a slide block model included in fuzziness meaning as the measure error and the model disagreement to an actual behavior in the time of debris running down on the slope.
In using the block slide model, the resistance force originated from the debris running down velocity should be considered except for the resistance force due to kinematic rigid friction. To carry out the prediction of run-out distance with higher accuracy, it is necessary to clarify the index of fluid friction coefficient than the fluid content rate in debris mass. The good agreements between the analyzed run-out distances and observed data are also demonstrated.