Variation analysis of multiple tsunami inundation models

Researchers have developed tsunami inundation models based on nonlinear shallow water equations to estimate tsunami propagation and inundation. However, their empirical results are not in perfect agreement with those of other research institutes, even though the same governing equations are used. Therefore, we quantitatively evaluated the variability of tsunami simulations in this study. Several research institutes have conducted tsunami simulations under the same input conditions using tsunami inundation models adopted for tsunami hazard assessment, resulting in a certain degree of variability among them. By examining the spatial and temporal differences in various physical quantities, we identified the characteristic topography where the variability between tsunami simulations increases. A novel method for calculating statistics from the area integrals of physical quantities was proposed to demonstrate the variability in the overall simulation results. In addition, the effects of different setting parameters and computational environments on the simulation results of a single model were evaluated. The findings of this study are expected to not only serve as a basis to verify the reliability of source codes employed by users of the tsunami inundation model, but also contribute useful technical information to advance probabilistic tsunami hazard assessment in the future

Elucidation of wave pressure acting on a wave-cut notch beneath a coastal cliff based on laboratory experiments and numerical modeling

To investigate past extreme waves which deposited cliff-top boulders, it is important to elucidate the wave force acting on wave-cut notches beneath coastal cliffs. Our laboratory experiments have revealed that extreme waves over coastal cliffs generated both sustained and impulsive forces, and that sustained forces can be estimated from buoyancy, because velocities are rather small when sustained forces are generated. Thus, boulders at coastal cliffs are likely moved by impulsive forces but not by sustained forces. We have also proposed coefficients of the formula which can reproduce impulsive and sustained wave forces acting on the notch based on observed and simulated wave heights and velocities. Using the proposed formula, wave heights and velocities that are necessary to move boulders up coastal cliffs can be estimated without numerical simulations. In our future investigation, we will account for the scaling effect of impulsive forces acting on coastal cliffs.Submitted/Accepted versionThis work was supported by a Fukada Grant-in-Aid FY2020 from the Fukada Geological Institute to Masashi Watanabe and JSPS KAKENHI Grant Number 21H00631, 22K14455. This work was also supported by a Sasakawa Scientific Research Grant from the Japan Science Society. This work was also supported by Association for disaster prevention research

Sensitivity analysis of the physics options in the Weather Research and Forecasting model for typhoon forecasting in Japan and its impacts on storm surge simulations

Weather Research and Forecasting (WRF) model is useful for forecasting typhoons as an external force of storm surge forecasts. This study examines the variation in typhoon forecasts caused by different choices of arbitrary physics options in WRF and their influence on storm surge forecasts. Eight frequently used combinations of cloud microphysics and planetary boundary layers were extracted via a review of previous studies. Subsequently, sensitivity analyses of these physics options were performed, targeting nine typhoons that landed in Japan during 2015–2019.  Additionally, we conducted case studies of storm surge ensemble forecasts in Tokyo Bay and Osaka Bay using WRF-simulated typhoons generated in the sensitivity analysis. As a result, the ensemble mean of the forecasts was comparable to the storm surge reanalysis simulation results obtained using an empirical typhoon model wherein the best track data is integrated to reproduce atmospheric fields. This may be attributed to the fact that the typhoon parameters (intensity, size, approaching angle, and velocity) obtained from the best track at landfall were generally within the range of the parameters that were simulated using WRF.Published versionThis research was conducted as part of the Earth Simulator application project “Superimposed Disasters of Heavy Rainfall, Storm Surge and Tsunami” (Research director: T. Arikawa) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and utilized the computing resources of the Earth Simulator. The work was also supported by “Collaborative Research Project on Computer Science with High-Performance Computing in Nagoya University”

A Coupling Simulation Between Soil Scour and Seepage Flow by Using a Stabilized ISPH Method

In 2011, the example that breakwaters collapsed because of the basic ground’s destabilization was reported by Tohoku-Kanto earthquake tsunami. Fluid-Structure-Soil coupling simulation is desired for a systematic comprehension of the breakwater collapse mechanism, and it may help to develop next disaster prevention method. In this study, A particle simulation tool based on the SPH has been modified and improved to analyze seepage flow and soil scouring. In seepage flow analysis, as a first step, this simulation treat the surface flow and seepage flow interactions by using governing equation. In the scouring analysis, soil scour is judged by an empirical criteria based on quicksand quantity formula