[Survive & Thrive] Introducing new rain alerts and why you should pay attention

Deadly flash flooding in Seoul in 2022 summer behind the development of a new mobile alert system

A pedestrian walks with an umbrella near Gwanghwamun Square in Seoul on Monday. (Yonhap)

Living in South Korea involves learning to differentiate between various mobile phone alerts and announcements, and deciding which ones to heed and which ones to disregard.

These alerts, sent by different authorities such as police, city government and central governmental ministries, may seek assistance in locating missing persons, inform of air quality unsafe for outdoor activities, or warn about occasional trash-carrying balloons sent by North Korea.

This summer, there is a new addition: torrential rain and flash flood alerts.

Sent by the Korea Meteorological Administration, these messages warn of extreme downpours, which have become increasingly frequent during summer in Korea.

The threshold for issuing the emergency alert is at least 50 millimeters expected to fall in one hour, resulting in over 90 millimeters within three hours, or 72 millimeters under one hour.

While the KMA's existing weather advisory system warns of expected precipitation, indicating the overall severity level of the weather event, the mobile alerts are intended as direct messages to prompt receivers to take immediate action, including evacuation.

The service was first introduced as a pilot project in Seoul last year, in response to deadly flash flooding in the summer of 2022 that resulted in 8 casualties.

Among the victims were a family of three who died in a flooded semi-basement home in southern Seoul and a sister-brother duo who were swept into an open manhole on a flooded street in Gangnam, southern Seoul. The rainfall at its peak was recorded at 141mm per hour, which was the capital's heaviest in 80 years.

The new torrential rain alert system has expanded to cities like Gwangju and Daegu this year. On Monday, alerts were sent to Andong and Yeongyang in North Gyeongsang Province, where 25 residents had been stranded in flash floods. All are safe, either rescued or having escaped the flooded area.

This was also the first time a flash flood alert was sent to people outside Seoul.

At 3:30 a.m. Monday, Andong's Ok-dong recorded 52.5 millimeters of rain in one hour and 103 millimeters over three hours. Yeongyang-eup in Yeongyang recorded 52 millimeters in one hour and 108.5 millimeters over three hours by 3:53 a.m.

The weather agency data shows 776 instances -- spread across 152 days-- over the past decade where rainfall severity could have triggered emergency alert messages. Around 82 percent of these cases occurred between July and September, coinciding with monsoon and typhoon seasons.

The frequency of heavy rain events requiring emergency alert messages has been increasing by an average of 8.5 percent annually over the last decade. This trend is expected to continue, according to the KMA.

Survive & Thrive is a series offering a guide to living in South Korea for those born outside of the country. – Ed.

By Song Seung-hyun(ssh@heraldcorp.com)