Energy Method for Approximating Overland Tsunami Flows

This paper applies a simple energy method to predict characteristics of overland tsunami flows based on extrapolation of the energy grade line between the shoreline and the tsunami run-up limit. Starting with a mapped run-up or inundation limit from tsunami hazard maps or from field surveys, the method reconstructs maximum inundation depths and velocities across a flooded topographic transect to the shoreline. The energy method is evaluated first in comparison with thousands of numerical simulations conducted on idealized topographies using a free-surface wave model. The method is then evaluated in more detailed simulations over realistic topography using a second tsunami-evolution model. Finally, the method is evaluated against field observations of inundation depths from tsunami events in Chile and Japan. In all cases, inundation depths are predicted quite well, with little bias across a wide range of flow conditions and topographic conditions. Predicted velocities show less precision but seem to predict the general velocity decay from shoreline to run-up limit. The method then overestimates and provides a conservative estimate of the maximum momentum flux. (C) 2017 American Society of Civil Engineers.