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Monday, Jan. 17, 2005

Underground flooding a big risk here: U.N. expert

Staff writer

Cities like Tokyo with sprawling underground facilities need better measures to minimize casualties should subways or shopping areas become flooded by heavy rains, according to a United Nations University researcher.

Srikantha Herath, senior academic program officer of environment and sustainable development at the U.N.U. in Tokyo, said in an interview with The Japan Times that the past few decades have seen a rush of construction of such structures in numerous developed countries, largely due to limited space above ground.

But he warned that the potential risks from flooding have not been recognized fully by the public in such countries, including Japan.

"Japan has one of the largest number of underground transportation (networks) in the world," said the Sri Lankan, an expert on hydrology and a former University of Tokyo professor. "If you think that a bank of a big river in the city broken (by heavy rains) and whole underground spaces like subways are flooded, it is very scary and (such a situation) can cause much panic."

Herath is one of the experts who will be attending the upcoming forum in Kobe on the impact of natural disasters on urban cities and strategies to tackle such situations. The World Conference on Disaster Reduction of the U.N. will run Tuesday to Saturday.

The scholar pointed to the fact that the Dec. 26 earthquake and ensuing tsunamis that struck the Indian Ocean region were unexpected in terms of scale.

Similarly, extremely heavy rains or floods never before experienced could strike underground structures, Herath said, adding he expects that measures to tackle such hazards will be discussed at the Kobe conference.

One precaution would be to construct entrances that are above ground level, which would prevent water from entering underground spaces, Herath pointed out. It is also important to establish evacuation and warning systems for subterranean facilities, he added.

To secure evacuation routes, Herath said underground structures should be connected with passages so people can escape through other underground structures if the entrances to one are blocked due to rising water.

While some underground complexes in Japanese cities have many exits to the surface, many do not, he added.

As a way of warning people who are underground about flooding, Herath suggested it would be effective to set up monitors in underground structures that automatically show the places that are flooded and where safe passages to the surface are located.

"Because you cannot see water coming (when you are) underground, one (effective way) would be to show graphically how the water is coming," he said.

Although central and local governments can improve infrastructure to tackle water-related disasters, Herath stressed that the public needs to become better aware of the risks of underground spaces in case of a flood, such as by using hazard maps provided by many local governments in Japan.

"Individuals should know of the possible dangers in an underground space in case of floods and be responsible for their own safety" by ascertaining evacuation routes, he said.

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The Japan Times

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