Hualien's Wanli River Landslide Lake Nears Overflow; Dam Breach Time Highly Uncertain

Authorities are closely monitoring the Wanli River landslide lake in Hualien County, Taiwan, as water levels approach a critical point. The current water level stands at approximately 1087.2 meters, with overflow anticipated around this evening as it nears the 1087.5-meter mark. The Forestry and Nature Conservation Agency's Hualien Branch reported that aerial surveillance this morning showed continued turbidity from the lower slope of the natural dam and increased seepage from the upper slope.

Concerns are high regarding the potential for dam failure. The agency outlined two primary scenarios: overflow erosion, which could lead to a breach, and internal erosion. Internal erosion, characterized by seepage and "pipe jacking" (管湧破壞), could weaken the dam structure, particularly thinner upper sections. This could result in a partial collapse and sustained overflow, further eroding the dam. The process could be exacerbated by debris falling from the right bank, potentially blocking the overflow outlet and prolonging the breach.

The timeline for a potential breach remains highly uncertain, with estimates ranging from several hours to several days, depending on rainfall, upstream water inflow, and the dam's material integrity. The remote location of the lake, inaccessible by road, necessitates reliance on aerial surveillance and water level monitoring.

Earlier today, a water level gauge experienced an anomaly. Experts explained that the primary gauge has a limited measurement range and was exceeded by the dam's increased height. A secondary gauge was deployed, but signal delays due to obstructions have been noted. Despite the uncertainties, multiple aerial survey teams are continuously monitoring the dam's condition and lake changes. The forecast for afternoon thunderstorms adds another layer of unpredictability to the situation.