Long-Term River Plans Revised for Climate Change

In response to the increasing frequency of water-related disasters in recent years and forecasts that they will become even more severe due to climate change, efforts are under way to revise the assumptions underlying flood-control plans. The policy is to shift from plans based on historical rainfall records to plans that account for climate change impacts and to promote fundamental flood-control measures.

For the Teshio River, Kuji River, and Naka River systems, the basic river improvement policies were revised in consideration of future increases in rainfall and from the perspective of basin-wide flood management. Revisions to the basic river improvement policies for each river system will continue.

Directions were presented for promoting basin-wide flood-management measures to reduce flooding that exceeds the design flood discharge, flood damage during the course of improvement works, and inland flooding.

To address the increase in flood forces caused by climate change, the scale of floods serving as the target discharge for long-term river improvement, namely the design flood discharge, was revised.

To accommodate the revised design flood discharge, the channel allocation discharge handled by rivers and the flood-control discharge handled by floodwater storage facilities were examined.

As specific directions for basin-wide flood management, the policy presented the promotion of measures including forest development and conservation, securing floodwater retention functions through preservation of open levees, raising of homes, construction of ring levees, and paddy field dams.