Hualien: Authorities in Hualien County are preparing for possible large-scale evacuations as Typhoon Fung-Wong approaches Taiwan, with officials warning that extreme rainfall could trigger the formation of a new landslide lake on Matai’an Creek.

According to Focus Taiwan, the Forestry and Nature Conservation Agency (FNCA) stated that a new barrier lake could form if three extreme conditions occur simultaneously: 24-hour accumulated rainfall of 800 millimeters, the collapse of the existing Matai’an Creek barrier lake holding about 1.5 million cubic meters of water, and a massive slope landslide blocking the river channel.

If these conditions are met, the resulting lake could store up to 15 million cubic meters of water and, if it later collapses, could unleash floodwaters at a peak rate of around 4,500 cubic meters per second, the agency estimated.

Monitoring data from Sunday showed the current Matai’an Creek landslide lake’s water level at 1,019.5 meters, with a volume of about 1.49 million cubic meters, which is only 1.6 percent of its pre-overflow level.

The downstream slope remains stable, with no signs of major collapse, according to the FNCA.

With forecasts of nearly 282 mm of rain over the next 48 hours, the FNCA’s Hualien Branch issued a yellow alert Sunday morning and sent emergency cell-broadcast messages to residents downstream, urging them to follow evacuation instructions if a red alert is issued.