On Dec. 11, the land ministry released a new policy vision for dealing with floods in response to September’s typhoon-triggered breach of the Kinugawa River, which inundated residential areas of Joso, Ibaraki Prefecture, stranding thousands for hours, and some for days.
The policy vision calls for wide-ranging measures to change the way floods are dealt with both at the national and local levels within the next five years. They include expanding existing embankment projects, training municipal leaders on when to issue evacuation warnings, and improving flood hazard maps.
Here are basic questions and answers on Japan’s flood management policy:
How serious was the Kinugawa flooding?
Typhoon Etau, which hit eastern Japan on Sept. 10 and 11, brought unprecedented levels of rain in many areas, including in Nikko, Tochigi Prefecture, which saw 551 mm of precipitation over a 24-hour period.
Along the Kinugawa River, which runs through Tochigi, Ibaraki and Chiba prefectures, banks overflowed and ruptured, flooding 40 sq. km, a third of the city of Joso, for days.
Two people were killed in Joso, thousands of houses and other structures were destroyed and 4,300 residents were rescued by authorities, including hundreds who were airlifted.
While floods are seasonal occurrences in Japan, the number of people who were unable to escape in time was unprecedented in recent history, the land ministry report says, adding that it took 51 drainage pump cars working around the clock for 10 days to remove all the water from the flooded residential areas.
Is the Kinugawa the only river vulnerable to floods?
No. The Land, Infrastructure, Transport and Tourism Ministry said in the vision report that climate change has increased the chances of rain overwhelming river banks nationwide. The ministry also concedes that its longtime policy of aiming to prevent floods by containing all rainwater within the rivers is no longer realistic.
For decades, the land ministry has taken the “hard” approach to flood control, under which it has tried to prevent floods by building dams upstream, dredging riverbeds and constructing levees.
“We need to share the awareness, across the entire society, that we cannot rely on past experiences, that the anti-flood facilities have their limits … and that we need to be proactive in dealing with disasters,” the report said.
What are the key points of the new vision?
The new vision breaks down into two major issues: “hard” and “soft” measures. The hard measures are a continuation of existing river embankment projects, through which 3,000 km of banks will be fortified within the next five years to improve their ability to withstand downpours. Measures include covering the top layer of the existing levees with asphalt and reinforcing the bottom section of the banks with concrete blocks to make them less prone to ruptures.
The soft measures, meanwhile, call for better coordination among officials on evacuation planning and sharing of real-time information with residents to alert them to the possibility of flooding. The ministry said it will establish regional councils made up of representatives from river management agencies, prefectures and lower-level municipalities to coordinate their emergency responses.
Kei Yoshimura, a hydrologist at the University of Tokyo’s Atmosphere and Ocean Research Institute, said the move to create regional councils is commendable, as coordination is key in disaster management. “It’s good that (the ministry) calls for improved awareness of all stakeholders,” he said.
Also, in an apparent response to criticism that the city of Joso was late to issue evacuation orders in September, the ministry said municipal heads will be briefed in advance, by the next flooding season, on exactly how to utilize flood alerts provided by river management agencies when they issue evacuation orders. By the end of fiscal 2020, all 730 flood-prone municipalities are to have prepared detailed evacuation plans and carried out drills. Currently only 216 municipalities have such detailed plans in place.
The report also said flood hazard maps should be improved.
What’s wrong with current hazard maps?
Municipalities are mandated by law to draw up flood hazard maps. But most residents are not aware of the maps or not sure how to use them, as they are not detailed enough to point out the exact levels of danger for each household and where and when each resident should evacuate, experts say. The land ministry, in a separate move on Dec. 10, launched a new committee of outside experts to guide municipalities on how to revise such maps to make them more user-friendly.
Is the vision good enough?
Yoshimura said he thinks it’s significant that the ministry has clearly acknowledged the limits of trying to prevent floods and calls for a range of measures that do not rely on massive public works projects.
He added, however, that the report fails to mention the need to improve the accuracy of flood forecasts. Long-term flood forecasts would help people prepare for evacuations, he said.
The government currently forecasts basic flood risks, based on past rainfall data and monitoring of water levels in rivers.
“Why aren’t there flood forecasts just like weather forecasts, which predict weather conditions days ahead?” he said. “Right now, authorities can predict floods only hours before they occur.”
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