Simulating floods triggered by volcanic activities in the Cheon‐ji caldera lake for hazards and risk analysis

Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Explosive volcanic activity, uplift of the lake floor and landslides directed into the lake are some of the possible scenarios that can cause the release of water through a breach. In this paper, we derive a physically based model that uses the mass balance equation to simulate the hydrograph through a breached rim due to water displacement by lake floor uplift or landsliding. The model was applied to the Baekdusan volcano to examine its performance. Then, the hydrograph at the breach of a caldera lake serves as an upstream boundary condition for the subsequent flood-routing model, FLO-2D. The FLO-2D simulation shows that three populated towns are at risk, showing maximum depth up to 10-30 m. The flow converges to the Baishan dam that has a volume capacity of 6.5 km(3). The simulation shows the probable inundation zones and maximum depth, and these are to be used for risk assessment.