Lesson learned from the breaching of super large, short-lived Mataian landslide dam: The importance of risk communication of a catastrophic and uncertain disaster

Landslide dams are usually short-lived and it is challenging for decision makers to take response for emergency management of dam breaching hazards. To make a proper decision becomes more difficult due to the high uncertainty for predicting the forming and breaching process of nature damming lake. Since one order of magnitude estimation error of peak flow is common, risk communication plays a vital role for managing the dam breaching hazards. The breaching of Mataian dam with a dam volume of 300 mega cubic meters on 23th Sep. 2025 in Taiwan, which killed  19 people and 5 people still missing, provides a unique case to learn the importance of risk communication and risk management for hazards relating to landslide dam breaching. In this presentation, the uncertainties related to dam forming identification, dam stability evaluation, breaching hydrogram estimation, and downstream flooding prediction are illustrated. This presentation tries to raise an open question: if this event start all over again, can the emergency response be improved and the number of victims can be reduced?