Sediment disaster hazard map and warning and evacuation viewed from laws and regulations as well as administrative documents

Mutsuo KAWAI


Provision of information about sediment disaster by administrative authorities (efforts to inform) and comprehension of the information by residents (efforts to learn) are expected to work concurrently for sediment disaster prevention. According to the Sediment Disaster Prevention Act (Act No. 57of 2000) and its regulation, mayors should create and disseminate sediment disaster hazard map when sediment disaster prone zones are designated by governors under the Act. The hazard map must provide for risk information including sediment disaster prone zones, dispositions for transmission of disaster information as well as evacuation ways and sites. The hazard map can also provide for other information deemed necessary to ensure alarming and evacuation operation. Sediment disasters caused by recent heavy rains prompted the Japanese government to introduce <5stages of alert level>. Each stage represents different level of urgency of sediment disaster. Disaster information framework is reorganized so that each information corresponds to one of the 5stages. It enables residents to realize urgency of sediment disaster and take appropriate evacuation behavior. On the other hand, each resident is expected to make for itself judgements about individual and familial evacuation behavior. These judgements cannot be entirely made collectively because they depend on personal, social and spatial condition of each resident. Improvement of information doesn’t mean that individual judgements become unnecessary. Support and facilitation of individual judgements about evacuation behavior is an important challenge of sediment disaster prevention. Residents are encouraged to enhance consciousness and preparedness through participation in formulation of the hazard map. Other community‐level initiativess such as community disaster prevention plan shall be used in connection with the hazard map.

Key words

sediment disaster, hazard map, 5stages of alert level