202510/29
The Yilan Branch and Hualien Branch of the Forestry and Nature Conservation Agency (FANCA Yilan and FANCA Hualien), along with a construction team, continued excavation and diversion operations at the Swallow Grotto landslide dam this morning (10/29). At approximately 11:25, on-site personnel observed a gradual increase in overflow volume. FANCA Hualien immediately issued an alert notice and CBS text message, instructing personnel at the Eastern Taiwan plants of the Taiwan Power Company to evacuate and clear the downstream river channel. The Xiulin Township Office was also asked to notify residents in low-lying areas to evacuate, while railway and highway authorities were notified to be on alert. By 11:40, the landslide dam had nearly completely breached, releasing all remaining water downstream. However, due to effective preventive measures, all personnel and facilities downstream of the Liwu River were safe.
FANCA Hualien explained that at 11:25 today, on-site construction workers discovered increasing overflow from the dam crest. All on-site personnel were immediately evacuated safely, after which erosion signs appeared on the dam structure. At 11:30, the erosion intensified, and the dam gradually breached. At 11:40, the dam had almost completely washed away, with the vast majority of the dam’s water surging into the lower reaches of the Liwu River. According to monitoring by the National Cheng Kung University team, the largest flood peak downstream occurred at approximately 11:50, raising the water level at the Jinwen Bridge piers by approximately two meters. After the flood peak, no disaster occurred in the lower reaches of the Liwu River. The water level of the original landslide dam has now dropped to the original river level. Although small amounts of residual dam debris remain scattered in the river channel, forming minor water retention zones, they no longer pose a disaster risk to downstream areas.
The FANCA will continue monitoring the residual dam structure and river channel changes in collaboration with the Disaster Prevention Research Center of National Cheng Kung University to assess safety conditions. Currently, the water level of the Liwu River has gradually stabilized. Personnel are conducting safety inspections before lifting the alert. Once it is confirmed that there is no danger, an alert termination notice will be issued. The public is reminded not to enter the river channel before the alert is lifted.
The FANCA expressed its gratitude to the personnel of FANCA Yilan and FANCA Hualien for their tireless and seamless cooperation in successfully defusing the Swallow Grotto landslide dam crisis. The FANCA would also like to express a special thanks to Mr. Huang Kuo-Bao, the on-site manager of Jingfu Construction Co., Ltd., and his team. With their high level of expertise, extensive experience, as well as their conscientious and responsible attitude, they successfully mitigated the risk of the landslide dam with minimal cost and time.