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Fence Being Built To Block Tsunami Debris From Sendai Port
May 03, 2017

SENDAI--A barrier costing 1.4 billion yen ($12.54 million) and stretching 4 kilometers is being built around Sendai port to prevent drifting shipping containers and vehicles from smashing into the city if another huge tsunami strikes.

The fence cannot stop seawater, but it is designed to withstand the impact of a 40- to 50-ton container.

Construction started in December 2015.

About 1,000 steel pipes measuring around 80 centimeters in diameter at the widest point will be driven into the ground several meters apart in the middle of roads surrounding the international port. Cables 1 to 2 cm in diameter will be stretched through the posts.

The steel columns are around 3 to 4 meters high. Their tops are set at about 7 meters above sea level, a meter higher than the tsunami that inundated the coastal area of Miyagi Prefecture in March 2011.

Although the height of the tsunami was relatively low in the prefectural capital of Sendai due to the flat topography, it was enough to float heavy objects.

According to the prefectural government’s department of harbors, 2,000 of 4,000 containers at the shipping yard were washed away by the tsunami. Some of them drifted inland, destroying buildings or blocking roads.

Several hundred passenger cars waiting to be shipped from the port were also carried away. Fuel in their tanks caused widespread fires among the tons of tsunami debris.

The prefectural government is also building 4-meter-high concrete seawalls along the port within the fence.

Under the plan, the seawall would block a tsunami of a scale that strikes “once in several decades or once in 100 to 150 years” under the central government’s definition. If a larger “once-in-millennium” tsunami occurs, the fence would reduce the damage to the city.

According to an expert, the fence at Sendai port will be one of the largest such structures in Japan.

Most of construction costs are covered by the national budget for reconstruction from the 2011 disaster.

The idea of building a debris-catching fence around harbors and ports came about after a tsunami was triggered by an earthquake off the southwestern coast of Hokkaido in 1993.

In the Tohoku region, a 460-meter-long fence around Hachinohe port in Aomori Prefecture was completed in 2016.