10/04 Expert: Residences should be moved to higher ground

Yasushi Kaneko / Yomiuri Shimbun Staff Writer

The government should consider moving residents living in low-lying costal areas to higher ground, according to a specialist in coastal engineering.

Waseda University Prof. Tomoya Shibayama has inspected the areas affected by the tsunami caused by the March 11 earthquake via helicopter. "More than half of the breakwater in Kamaishi, Iwate Prefecture, was destroyed by the tsunami, and the one in Ofunato was no longer visible," he said.

Towns on the Sanriku coast have long experience with tsunami, including notable tsunami caused by domestic earthquakes in 1896 and 1933, as well as one following a quake in Chile in 1960. According to Shibayama, these tsunami measured about four meters at the tallest at Onagawacho, Miyagi Prefecture.

The March 11 tsunami in the town, however, was more than four times this height, he said, and came with force of dozens of tons per square meter, similar in strength to the 2004 Indian Ocean tsunami that killed more than 230,000 people.

Tsunami after the March 11 earthquake were much bigger than those anticipated in disaster action plans made by towns on the Sanriku coast, effectively rendering their protective measures meaningless, Shibayama said. "It's clear now that breakwaters and seawalls don't do much to protect residential areas from tsunami," he said.

To preserve regional communities, local governments should consider revising their land-use programs and move low-lying residential areas near the sea to higher ground, Shibayama said.

The village of Ultogia, Samoa, was hit by the 2009 tsunami and about a month later, neighborhoods near the sea began moving to higher ground. "In Japan, the central and prefectural government should take the initiative [and implement similar policies] because of the difficulty of coordinating the rights [of the affected parties]," he said.

The central and local governments also need to increase the tsunami size their disaster action plans are predicated on and revise evacuation plans based on even larger tsunami, he said.

The central government's tsunami guidelines stipulate that citizens should seek refuge on the third floor or higher of buildings built of reinforced concrete. However, according to officials of Minami-Sanrikucho, Miyagi Prefecture, people on the roof of a four-story building said the tsunami reached their knees, about 15.5 meters above the ground.

"Residents need to evacuate to areas about 18 meters high, equivalent to a building's sixth floor," Shibayama said.

(Apr. 10, 2011)