Seoul to build deep underground rainwater tunnels in 6 flood-prone areas

This photo released by the Seoul City Government shows a map of the deep underground stormwater storage and drainage tunnel built in the Sinwol district, southwest of Seoul. (Seoul City Government)

The Seoul city government has unveiled medium- and long-term flood prevention measures centered on the construction of deep underground stormwater storage facilities in six flood-prone areas.

According to measures announced by Mayor Oh Se-hoon on Wednesday, the city government will spend 1.5 trillion won ($1.15 billion) over the next decade to build six stormwater storage and drainage facilities. large-scale, also called deep underground tunnels.

The underground tunnel project involves the construction of large-scale drains of approximately 10 meters in diameter each at a depth of 40 to 50 meters underground.

The measures came after the heaviest downpours in 115 years hit the Seoul metropolitan area earlier this week, leaving at least 16 people dead or missing and more than 2,500 homes and buildings submerged. A total of 525mm of rain fell in Seoul from Monday to Wednesday morning, causing widespread flash flooding across southern Seoul.

In the first phase of anti-flood measures, the city government will construct underground rainwater storage tunnels in three areas around Gangnam Railway Station in Gangnam Ward, Dorim Stream in Gwanak Ward and Gwanghwamun in central Seoul by 2027.

In the Gangnam district, hardest hit by this week’s downpours, the underground tunnel will be designed to withstand heavy rains of up to 110mm per hour, the government added. Areas south of Seoul have been hit with torrential rains of more than 100mm per hour this week.

The deep underground rainwater tunnel project was originally announced by Oh during his previous term as mayor in July 2011.

But the project was scrapped due to budget concerns after his successor Park Won-soon took office in October of the same year. Instead, Park’s government built just one of Oh’s proposed seven underground tunnels in Seoul’s southwestern Sinwol district.

The Sinwol stormwater storage facility, which can handle 95-100mm of rain per hour and accommodate 320,000 tons of water, was completed in May 2020. The area did not suffer serious damage from flood this week. (Yonhap)

Bonny J. Streater