Hualien on alert for possible new landslide lake as typhoon nears

Taipei, Nov. 9 (CNA) 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.

The Forestry and Nature Conservation Agency (FNCA) said Sunday 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 on 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 -- 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.

Guangfu Township, located downstream of the creek, has begun preparations for potential evacuations affecting more than 5,500 residents, according to township chief Lin Ching-shui (林清水).

Plans include relocation to seven designated shelters, staying with relatives, or moving to higher floors in homes, Lin said, adding that about 1,420 people are expected to take shelter in evacuation centers such as Guangfu Elementary School and Fuyuan Junior High School.

Lin said shelters would be set up Monday morning, and evacuation will begin once a red alert is issued.

Households that were submerged by more than 1.5 meters of floodwater during the overflow of the Matai'an barrier lake on Sept. 23 will be required to evacuate rather than shelter in place, he added.

The Central Weather Administration said earlier that a sea warning for Typhoon Fung-Wong could be issued as early as Monday afternoon.

The typhoon's outer circulation, combined with a northeasterly wind system, is expected to bring extremely heavy to torrential rain to northern and eastern Taiwan, particularly the Taipei and Yilan-Hualien regions, the agency said.

The CWA forecast the storm will pass near Luzon in the Philippines before entering the South China Sea and potentially turning northward toward Taiwan.