Hualien's Wanli River landslide dam shows less water storage than expected; seepage suspected

Concerns are mounting over the Wanli River landslide dam in Hualien, Taiwan, as its water accumulation is falling short of expectations, with aerial surveillance indicating potential seepage through the dam body. The Forestry and Nature Conservation Agency's Hualien Branch issued a red alert due to continuous rainfall, but subsequent aerial surveys revealed that the dam's water storage increase was lower than anticipated.

Officials suspect that as the water pressure rises within the dam, water may be seeping through internal pores. This seepage could potentially lead to internal erosion, a precursor to pipe jacking, a dangerous phenomenon where water erodes internal passages, potentially causing catastrophic failure. The agency is closely monitoring the situation, particularly the water levels of downstream bridges, and has warned against any personnel entering the riverbed.

While current weather forecasts do not predict the dam reaching its overflow point imminently, the possibility of pipe jacking remains a significant worry. The estimated inflow of water was 400,000 cubic meters, but only 220,000 cubic meters were stored, with an estimated 180,000 cubic meters lost to seepage. This discrepancy highlights the urgency of the monitoring efforts to prevent any potential disaster.

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The team initially assessed that as the lake's water level and pressure rose during storage, water might seep out through the pores within the dam body, resulting in an actual storage increase lower than expected. If the seepage water turns turbid, it indicates that fine materials within the dam are being carried away by the water flow, a sign of pipe jacking damage, at which point the alert should be immediately raised.