With sinkholes increasingly appearing across Seoul and city authorities declining to release detailed risk maps, concerned residents are stepping in—building their own tools to inform and protect the public.

Two citizen-led interactive maps have recently gained attention for visualizing sinkhole-prone areas using public data, news reports, and geospatial tools. These efforts emerged in response to the Seoul Metropolitan Government’s refusal to share its sinkhole risk assessments, citing concerns about “misunderstanding” and potential impact on property values.

One of the most prominent projects comes from Yoon Shin-young, a former science journalist. His map, available at sciencesay.shinyapps.io/sinkhole, compiles more than 1,400 sinkhole incidents reported nationwide over the past seven years, with filters by neighborhood, cause, and date.

“I’ve always been interested in using maps to communicate disaster-related information more effectively than text alone,” Yoon told The Korea Herald. “When a sinkhole appeared in Yeonhui-dong last year, I realized how hard it was to find meaningful public data. That’s when I decided to build the map.”

While some sinkhole data is technically public, Yoon said it’s often buried in complex portals and written in specialist language. “It’s not hidden, but not accessible to everyday people,” he said. By combining publicly available records and data obtained through requests, he created a tool designed to be user-friendly and regularly updated.

Yoon emphasized the importance of maps over static articles. “Risks like sinkholes evolve constantly. A map can be updated and reflect those changes in real time, which is something a news article or report can’t do,” he said.

Another initiative was launched on April 4 by a former web developer, currently on leave from work. His map—sinkhole-ebon.vercel.app—uses media-reported incidents over the past decade, with locations manually verified via satellite and street-view tools. It drew over 1,000 visitors in its first week. “If this helps people avoid danger, it’s worth the effort,” he said.

These grassroots efforts contrast sharply with the city government’s decision to withhold its full risk data. Since 2014, Seoul has tracked areas vulnerable to ground collapse, ranking them by risk level based on underground infrastructure and conditions. But officials argue that publicizing this could lead to public confusion and hurt real estate markets.

Yoon sees room for compromise. “I understand the government’s position—they’ve made incident data public, even if it’s hard to find. But what’s really needed now is transparency about future risks, like results from underground surveys. That’s still missing.”

Public concern surged after a deadly March 24 sinkhole in Gangdong-gu killed a motorcyclist and injured another driver. Local broadcaster MBC later revealed, through a public information request, that a 2024 city report identified 329 underground voids beneath Seoul roads—38 of them less than 20 centimeters below the surface and marked for emergency repair.

While 247 sites have since been addressed, dozens remain. And the problem is growing: sinkhole reports jumped from 67 in 2022 to 251 in 2024. Experts link this spike to aging infrastructure, heavy excavation work, and rapid urban development.

Yoon, who lives near ongoing subway construction in Suwon, said his personal experience adds urgency to his work. “Every commute felt risky,” he said. “I made this map to help people understand where and why these incidents are happening.”

mjh@heraldcorp.com