Community-based Flood Risk Management of urban and rural area in Kumamoto, Japan

According to recent statistics, heavy rainfall has become more frequent in Japan in recent decades. To mitigate personal suffering from flood disasters, it is helpful to resolve recognition gaps in information propagation. Although residents can receive large scale information on weather forecasts through mass media or the internet, local governments do not always provide the information necessary to the residents of flood-prone areas; in some cases, residents do not sufficiently understand disaster information. This study aims to develop tools to support community-based risk management that meets the needs of local residents for flood risk preparedness. We first present a case study of flood risk communication in Kumamoto, Japan. After discussing the needs of local residents, we introduce support tools.

A framework for community-based flood risk communication using continual workshops and flood evacuation drills based on the PDCA cycle was proposed and implemented. Through the continuation of the PDCA cycle, community flood risk mitigation would be expected to be enhanced. The cycle consisted of the following four stages: 1. Plan: Planning of disaster prevention countermeasures and evacuation routes. 2. Do: Introduction of planned countermeasures and routes. 3. Check: Observation and diagnosis after introducing the planned countermeasures and routes. 4. Act: Explanation of the results and feedback about the planned countermeasures and routes.

The study is conducted in both urban and rural region. In the urban area, in the central of Kumamoto city, Japan, the local community constructed in lowland area around the river. In this area, the first workshop started in 2006. Another rural area, started in 2008, is located in the mountain slope in the middle of Kyushu Island, Japan, where the population aging rate　is higher than 50%.

We held workshops involving both local residents and the staff of the local government office. In the workshops, the attendants discussed the hazard area in the flood or debris flow caused by severe squall, and constructed hazard map considering the local residents' information. The next step is to make a simulation using the Drill Imaging Game (DIG). Evacuation trainings were conducted assuming that the several roads was prevented by flooding.

After the series of the workshops and trainings, following needs of the local people were arisen: 1. Temporary evacuation spots should be established for each block 2. Real-time information, especially that regarding inland flooding, is insufficient 3. Ways to ensure the safety of vulnerable residents who need support during evacuation need to be considered.

With the above requests, we developed the following support tools. 1) the realtime monitoring system of inland flooding, with the water level of the channel observed at every one minute, 2) the wireless raingauge network for mountain region to monitor the local heterogeneity of the precipitation due to the mountain-valley orography, and 3) the safety confirmation support system using mobile phone and the GIS tools.