In the wake of a recent series of increasingly severe rain-caused disasters, the infrastructure ministry is discussing new steps to prevent river flooding, with an eye on expected increases in rainfall due to global warming.
The ministry will revise part of the government’s basic policy on river maintenance as early as this fiscal year after discussions at the Council for Social Infrastructure, which advises the infrastructure minister, officials said.
It will take into account a goal to limit temperature rises set by the Paris agreement, an international framework meant to combat global warming.
Abnormal weather due to global warming has become a problem in many parts of the world. In Japan, heavy rains hit the northern part of the Kyushu region in 2017 and western parts of the country in 2018. Strong typhoons have brought record downpours this year as well.
The Meteorological Agency has estimated that the number of occurrences of torrential rains of over 50 millimeters per hour has increased 40 percent in recent years from some 30 years ago.
With the number of such occurrences and amounts of rainfall expected to rise further, the ministry will make efforts to counter the situation by revising the policy.
The Paris agreement set a goal of keeping the rise in the average global temperature to less than 2 degrees Celsius compared with that before the Industrial Revolution.
The ministry will consider new policy measures in line with that goal.
For example, the ministry will switch to a new rainfall forecasting method that reflects climate change to guide efforts to strengthen river levees and water gates. It will also take into account the possibility of a further increases in rainfall from the forecasts under the new method.
In addition, the ministry will analyze expected landslides and other damage due to climate change and the mechanism of simultaneous occurrences of floods and high tides to consider effective measures.
To prepare for situations where unexpectedly massive floods hit dams and reservoirs, the ministry will discuss facility structural issues to lessen potential future damage.