Japan’s Flooding a Perfect Storm for Civil Engineering
Emily Pollock posted on July 11, 2018 |

At least 155 people have been killed and almost two million have been evacuated, after a week of historic rain and flooding in Western Japan. And, while officials scramble to ensure that survivors are found and engineering minds debate how to ensure the tragedy doesn’t happen again, Japan’s geology and geography pose a daunting challenge.

As the death toll climbs above 150, rescuers search for missing people in Hiroshima prefecture, western Japan. (Image courtesy of Sadayuki Goto, Associated Press.)
As the death toll climbs above 150, rescuers search for missing people in Hiroshima prefecture, western Japan. (Image courtesy of Sadayuki Goto, Associated Press.)

Over the last week, parts of Southwestern Japan have received almost three times the usual amount of rain for the entire month of July, as much as 10cm of rain per hour. Particularly hard-hit are Kurashiki and Hiroshimi, where river overflows contributed to flooding damage. According to Japanese authorities, the flooding is the worst the country has seen in 36 years.

For those in the impacted areas, the rain wasn’t the only problem: the flooding also caused hills to collapse in landslides, burying houses and streets under rivers of mud. And, while rescue workers have been able to return power to all but 3,500 customers, over 200,000 still do not have water. After a cabinet meeting on Tuesday, Finance Minister Taro Asocited the importance of restoring electricity and water in the face of high post-flood temperatures: "There have been requests for setting up air-conditioners due to rising temperatures above 30 degrees (86F) today, and at the same time we need to restore lifelines."

The government is responding strongly to the current crisis, mobilizing 75,000 emergency response workers and setting aside 70 billion yen (USD$845 million) to repair infrastructure. But for officials and civil engineers looking to ensure that the situation doesn’t happen again, the challenges are steep.

A large part of the problem is geographic. According to civil engineer Takashi Tsuchida, the casualties in Hiroshima prefecture were mostly from landslides in areas where housing was built up against steep slopes. Japan’s mountainous landscape and population density mean that many homes are built on non-ideal ground. “People have been living for 40 to 50 years in an area that had latent risk, but decades went by without disaster,” Tsuchida told reporters from Reuters. “But intense rainfall has become more frequent, and the hidden vulnerability has become apparent.”

Flood response is also more difficult because most residents are used to less severe flooding. According to Nobuyuki Tsuchiya, former chief civil engineer of Edogawa, some low-lying areas of Japan have been flooded approximately 250 times in the last 400 years. The frequent flooding means that residents are experienced at dealing with minor floods but less likely to take larger floods seriously. “We had evacuation orders before and nothing happened, so I just thought this was going to be the same,” Kurashiki resident Kenji Ishii told reporters. Like many others in the affected areas, Ishii and his family didn’t evacuate immediately after the government’s flood warnings.

While many of these areas were vulnerable to flooding before, recent changes in climate have caused heavier rains and stronger typhoons, making floods more dramatic and deadly. Climate change has made the project of flood-proofing Japan a race against time with civil engineers keeping an eye to the next possible natural disaster. In a New Statesman article this February, Tsuchiya discussed the methods in place to prevent flooding in low-lying Tokyo, like the Metropolitan Area Outer Underground Discharge Channel (MAOUDC), which uses jet-style engines to suck in water from overflowing rivers surrounding the capital. The MAOUDC, and the network of underground infrastructure meant to avert floodwaters from Tokyo, are feats of infrastructure. But there’s still concern over whether they’ll be effective against the increased rainfall; “To be frank, these measures are not enough,” Tsuchiya concluded.

The MAOUDC, the world's largest underground flood water diversion facility, is designed to avert floodwaters from Tokyo, but may not be sufficient in the face of storms exacerbated by climate change. (Image courtesy of Wikipedia.)
The MAOUDC, the world's largest underground flood water diversion facility, is designed to avert floodwaters from Tokyo, but may not be sufficient in the face of storms exacerbated by climate change. (Image courtesy of Wikipedia.)

Across the world, engineers and architects are having to adapt to a world where “extreme” weather events are becoming increasingly normal. And places like Japan, where history and geography put residents at distinct risk, are the front lines of that battle.

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