Outburst Flood from Barrier Lake Destroys Highway Bridge in Hualien

Super Typhoon Ragasa delivered extreme rainfall across eastern Taiwan, where a barrier lake that had formed from earlier landslide debris on Matai’an Creek abruptly failed. The outburst flood destroyed a bridge on Provincial Highway 9 between Fenglin and Guangfu, with authorities reporting at least 17 fatalities, dozens missing, and more than 7,000 people evacuated. Flow depths in parts of Guangfu rose to upper-storey elevations, and sediment-laden waters left extensive mud and debris across streets and properties.

The barrier lake, formed by landslide debris along Matai’an Creek, failed under the intense rainfall delivered by Ragasa. Eastern Taiwan recorded up to 700 mm of precipitation, which increased water levels beyond the stability of the natural dam. Once breached, floodwaters surged downstream, destroying the bridge structure and inundating residential areas. Reports indicated water levels reached as high as second floors in some homes. Sediment-laden flows left extensive deposits of mud and debris, further compromising local infrastructure.

Typhoon Ragasa brought winds exceeding 270 km/h and triggered widespread flooding, landslides, and transportation disruptions across Taiwan, Hong Kong, Macau, and southern China. In Taiwan, ferry services were suspended, over 100 flights were cancelled, and emergency evacuations were carried out in high-risk areas. The event demonstrates how barrier lake failures, combined with typhoon-scale rainfall, can result in sudden and destructive infrastructure losses.