Flood risk Hokkaido

Between August 17 and 23, 2016, Hokkaido (Japan) suffered from three typhoons. Another typhoon followed a week later. The exceptional heavy rainfall during these typhoons caused dike breaches with large scale inundations as a result. This led to damage of roads, bridges, railways and agricultural lands. In a changing climate the paths of typhoons will change, resulting in more of these events passing Hokkaido (The Prediction of Climate Change in Hokkaido, Japan, 2018). Hokkaido requires renewed water management planning, to be prepared for the consequences of such events that result from climate change.

In the Partners for Water project “Flood Risk Hokkaido” we analyze the flood risk for Hokkaido by using state-of-the-art flood risk methods that are developed and widely used in the Netherland (Veiligheid Nederland in Kaart, VNK2). To make this approach fit for use in Japan, additional failure mechanisms are added to the approach, such as dike failure due to meandering rivers or due to earthquakes. It is crucial to have a good understanding of the impact of future climate change on these events, so that the resulting extreme water levels can be properly estimated. For this we apply the official Dutch method for deriving extreme flood statistics (GRADE).

Parallel to these activities we exchange knowledge and develop a sustainable network of knowledge entrepreneurs. The project provides valuable knowledge on applying the Dutch approach for flood safety in Japan. This experience is also valuable to apply similar methods in comparable situations around the world.

The first beneficiary of the project is the regional committee called “Flood Disaster Prevention Committee Based on Extremely Heavy Rain in Hokkaido August 2016”. This committee was established by Hokkaido Regional Development Bureau (part of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT)) together with Hokkaido Prefectural Government. The committees mandate is to investigate flood prevention methods, by studying the effect of climate change on water management issues (securing production area). The second beneficiary of the project is the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). MLIT will use project results in Hokkaido will be used as a pilot for other prefectures (administrative units) in Japan that are facing similar issues.