TAIPEI (Taiwan News) — A nine-member survey team was airlifted from a remote barrier lake on the Wanli River in Hualien County on Saturday after completing a four-day scientific investigation.
The mission was cut short by one day due to the approach of Typhoon Bavi. Three helicopters were dispatched to a designated extraction point to airlift the team out. According to the Forestry and Nature Conservation Agency Hualien Branch, the team completed several key survey tasks, per a press release.
Geological measurements utilized the FieldMove Clino mapping system, and water samples were collected from the barrier lake and upstream waterways for laboratory analysis. The team also carried out close-range aerial photography of the spillway, landslide dam, and upstream terrain, while conducting on-site inspections of the dam structure, upstream inflow, and downstream outlet.
Additional work included testing communication signal coverage along the access route, identifying helicopter hoisting locations, and installing fixed ropes. The team also recorded a GPX route to establish a safer access path for future monitoring missions.
Aerial monitoring showed the lake behind the landslide dam continues to rise steadily. The team found no significant seepage or other structural abnormalities. As of 8 a.m. Saturday, water levels had reached 54.54% of the lake's estimated storage capacity of 5.1 million cubic meters, per the press release.
FANCA said the survey results will provide an important basis for future monitoring of the barrier lake and assessments of downstream disaster risks. Authorities will continue tracking changes in water levels and dam stability while adjusting emergency response measures as needed to protect downstream communities.
The mission began on Wednesday, when the team was flown into a landing zone before hiking approximately three kilometers to the barrier lake. During the operation, members identified an alternative helicopter evacuation site that reduced travel time for extraction.
Hualien Branch Director Huang Chun-tse (黃群策) said the geological data and water samples collected during the expedition will help experts better evaluate the stability of the landslide dam. He added that the ropes and route planning completed during the mission will improve access for future emergency surveys if conditions worsen, per UDN.
According to the agency, the barrier lake has recently received an estimated daily inflow of 150,000 to 250,000 cubic meters of water. Officials said no significant seepage or structural abnormalities have been detected, and, if current weather conditions persist, the dam is not expected to overflow within the next nine days.
