By TAMOTSU SUGAO/ Staff Writer
March 30, 2020 at 18:50 JST
HAMAMATSU, Shizuoka Prefecture--Construction is complete on one of the biggest breakwaters in Japan, a massive seawall built alongside coastal areas here to prevent flooding in the event of a tsunami.
The breakwater is up to 15 meters tall and stretches 17.5 kilometers in length.
It is expected to withstand a massive tsunami caused by a Nankai Trough earthquake and dramatically reduce flooding.
“It can dramatically reduce the disaster-causing damages,” said Takeshi Takada, chief of the coastal maintenance section of Hamamatsu’s civil engineering office in the prefectural government.
But Takada also cautioned the public to stay alert in the event of a disaster.
“I hope everybody takes the appropriate actions in the instance of an earthquake,” he said.
The wall covers the Pacific Ocean coastline in the city from the mouth of the Tenryugawa river in the east to Imagire-guchi inlet in the west, which connects between Lake Hamanako and the Enshunada Sea.
The total cost of the project is 33 billion yen ($306 million).
Housing company Ichijo Komuten group, established here and headquartered in Tokyo, donated 30 billion yen to the prefecture for the project, saying they wanted to show its gratitude to the area. The company began construction in March 2014.
According to an assessment of potential damages caused by a giant earthquake and tsunami, the completed breakwater is expected to reduce flooding in such an event from 4,190 hectares to 1,423 hectares.
A flood of two meters or higher, thought to be capable of washing away wooden houses, would now be reduced from 270 hectares to just six hectares in housing areas. The barrier is also expected to protect the JR Tokaido Shinkansen Line and Tokaido Line, leaving them hardly damaged by such a flood.
The project used the cement sand and gravel construction method, of mixing the cement and a high quality soil, which was also used in coastal breakwaters in Miyagi and Fukushima prefectures, allowing trees to be planted on top for added protection by mounting the soil.
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The breakwater is seen along the coastline in Hamamatsu, Shizuoka Prefecture, on March 18. (Hikaru Uchida)
