Abstract
“Sediment disaster prevention law”has become effective in Japan since April 1, 2001. It has been equipped with a newly-developed method to determine disaster-vulnerable areas. This methodology have a problem that it does not consider unique and complex characteristics of each individual slope or stream.
Hazard maps, without mentioning, must provide the information of disaster prediction to their users. In that sense, most sediment disaster hazard maps currently distributed among citizens in Japan are not“sediment disaster hazard maps”; they are“sediment disaster-vulnerable area maps. ”Some technical reasons why the study of the hazard mapping for sediment disasters has been less advanced include (1) there are less scientific records of actually occurred disasters compared to volcanic hazards and (2) the causing factors of sediment disasters are more complex than those of flood disasters, such as water level, flow velocity, etc.
In addition to the technical problems mentioned above, there is an organizational problem in the current way of utilizing hazard maps. In the case of the storm disaster taken place in Miyagawa village, Mie prefecture in September 2004, many people were killed by the disaster due to the late issuing of evacuation order, even though the residents were provided with an accurate disaster susceptibility map of the village. Information about the disaster-susceptible areas and evacuation sites on hazard maps prepared by municipalities in Japan is rarely taken into account in their regional disaster prevention plans including evacuation training. Therefore, how to improve the organizational aspect of the utilization of hazard maps has become very important issue in the field of hazard mapping, as well as the methodological improvement of hazard mapping.
