Building a flood hazard map due to magma effusion into the caldera lake of the Baekdusan Volcano

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. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. The volcano is showing signs of waking from a century-long slumber recently and the volcanic ash may spread up to the northeastern of Japan. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. Floods from lake-filled calderas may be particularly large and high. Volcanic flood may cause significant hydrologic hazards for this reason. This study focuses on constructing a flood hazard map triggered by the uplift of lake bottom due to magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by the past record from other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic model (Flo-2D) runs to simulate channel routing downstream. The final goal of the study stresses the potential flood hazard represented by the huge volume of water in the caldera lake, the unique geography, and the limited control capability. he study will contribute to build a geohazard map for the decision-makers and practitioners. Keywords: Effusion rate, Volcanic flood, Caldera lake, Uplift, Flood hazard map Acknowledgement This research was supported by a grant [NEMA-BAEKDUSAN-2012-1-2] from the Volcanic Disaster Preparedness Research Center sponsored by National Emergency Management Agency of Korea. Inundation map triggered by magma effusion simulated by Flo-2D