4.5 km Deep Underground Rainwater Tunnel Under Dorimcheon Stream... Seoul's Flood Defense System Begins in Earnest

A project to construct a deep underground rainwater drainage tunnel in the Dorimcheon Stream area, which has faced high risks of flooding due to rapidly rising water levels during heavy rains, is beginning in earnest.

The plan is to construct an underground tunnel with a total length of 4.54 kilometers and a maximum diameter of 12 meters in the Dorimcheon area by January 2030, dispersing and storing rainwater during heavy downpours to reduce the rise in Dorimcheon's water level and the risk of flooding in surrounding areas.

The Seoul Metropolitan Government announced today (June 23) that it has recently gazetted the implementation plan for the urban planning facility project for the construction of the deep underground rainwater drainage tunnel in the Dorimcheon area.

The project section runs from 459-5 Sindaebang-dong, Dongjak-gu to 87 Yeouido-dong, Yeongdeungpo-gu.

Under the urban planning facility classification, the project types are waterproofing facilities and a public square.

The area of the waterproofing facilities is 70,885 square meters, and the rainwater drainage tunnel will be constructed with a total length of 4.54 kilometers and a diameter of 10.4 to 12.0 meters.

A total of five vertical shafts will be installed to operate the tunnel.

These include one ventilation shaft, three inflow/outflow shafts, and one maintenance shaft.

The area of the urban planning facility square is planned to be 928 square meters.

The project operator is the Seoul Metropolitan Government, and the project period is from the date of the implementation plan approval notification to January 5, 2030.

A deep underground rainwater drainage tunnel is a disaster prevention facility that collects rainwater, which rushes into streams and sewer pipes all at once during heavy rains, into a large tunnel deep underground, thereby reducing the rise in stream water levels and the risk of urban flooding.

The Dorimcheon area borders residential and commercial zones, as well as living areas densely packed with urban infrastructure such as roads and railways.

When rain is concentrated in a short period, the stream's water level rises rapidly, repeatedly raising concerns about low-lying area flooding and stream overflows.

Indeed, Dorimcheon has been a major target of management by the Seoul Metropolitan Government and related agencies during every heavy rain event.

In July last year, the water level at the Sindaebang 1 Bridge point in Sillim-dong, Gwanak-gu rapidly rose from around 80 centimeters to over 2.5 meters in just 30 minutes, triggering a flood advisory.

In July 2024, while heavy rain warnings were issued across Seoul, flood advisories were also issued for Mokgamcheon and Dorimcheon, and access to 29 streams in the city was restricted.

This project is one of the key initiatives in the large-scale expansion of disaster prevention infrastructure that the Seoul Metropolitan Government has been pursuing since the record-breaking heavy rains in August 2022.

At that time, a record cumulative rainfall of 515 millimeters poured across Seoul, causing casualties and large-scale damage to facilities.

Critics pointed out that the existing disaster prevention system, centered on sewer pipes and rainwater pumping stations, had limitations in responding to extreme rainfall caused by climate change.

In response, the Seoul Metropolitan Government decided to raise its disaster prevention performance goal from the previous 95 millimeters per hour to 100 millimeters, and to resume the deep underground rainwater drainage tunnel project, focusing on flood-prone areas.

The areas around Gangnam Station, Gwanghwamun, and Dorimcheon are the targets of the first phase of the project, and the city aims to complete these sections by 2030.

Once the first phase is completed, a system will be established to reinforce Seoul's key flood-prone areas with large underground disaster prevention facilities, alongside the Sinwol deep underground rainwater drainage tunnel already in operation.

Following the notification of the implementation plan, the Seoul Metropolitan Government plans to take subsequent steps, such as land expropriation and use, and proceed with construction through the Urban Infrastructure Headquarters.

A Seoul Metropolitan Government official said, "We will make efforts to complete the first-phase deep underground rainwater drainage tunnels in Gangnam Station, Gwanghwamun, and Dorimcheon without a hitch to prevent casualties from wind and flood damage and minimize property damage."

(Photo: Yonhap News)
※ Please note: This article was translated by AI and may contain errors.