Effectiveness of Real-Time Near-Field Tsunami Inundation Forecasts for Tsunami Evacuation in Kushiro City, Hokkaido, Japan - Post-Tsunami Hazard: Reconstruction and Restoration - page 170

Inundation Forecasting (NearTIF) algorithm is developed to produce a reliable tsu-
nami inundation forecast map on high-resolution topography. The algorithm relies
on a precomputed tsunami database to ensure the promptness of the forecast.
The accuracy of a tsunami inundation forecast is directly related to the accuracy
of the tsunami source information. We may need to wait more than 5 min after an
earthquake occurs to obtain more data for a reliable tsunami source estimate. Once
a reliable tsunami source model is estimated, tsunami inundation can be simulated
accurately by solving the nonlinear shallow water wave equations. However, high-
resolution tsunami numerical forward modeling is numerically expensive. If we
conduct high-resolution tsunami inundation modeling in real time during an event,
we might not be able to obtain results before the actual tsunami hits the shore. The
NearTIF algorithm can give a tsunami inundation forecast map that is similar to that
obtained from numerical forward modeling, but in remarkably less run time.
We evaluated the effectiveness of using tsunami inundation forecast maps in the
real world by carrying out a tsunami evacuation drill in Kushiro City, Hokkaido,
Japan, involving the city residents. The drill was started by the announcement of a
tsunami warning to evacuate the residents to the nearest evacuation building.
Approximately 10 min after the announcement, a tsunami inundation forecast map
produced by the NearTIF algorithm was given to the participants in the drill. The
participants found that the use of the tsunami inundation forecast map was effective
in helping them make better decisions with high confi dence during the tsunami
evacuation process.
The NearTIF algorithm is recommended for use as part of the reconstruction
policy by local authorities to improve the evacuation effi ciency, particularly in
tsunami-prone areas. We also recommend the use of the NearTIF method for devel-
oping future tsunami forecasting systems with a capability of providing tsunami
inundation forecast maps for locations near the tsunami source area.
Acknowledgements This study was supported by the Ministry of Education, Culture, Sports,
Science and Technology (MEXT) of Japan, under its Observation and Research Program for
Disaster Mitigation of Earthquakes and Volcanic Eruptions. We thank Mr. Shunri Akamatsu and
Mr. Takumi Sato for their help in preparing this manuscript. We thank the reviewer for the valuable
suggestions and comments. The bathymetric dataset used for tsunami simulation is based on the
General Bathymetric Chart of the Oceans (GEBCO) 30 arc-sec grid resolution, Japan Hydrographic
Association's M7006 and M7007 bathymetric contour data, and digital elevation model (topo-
graphic data) of Geospatial Information Authority of Japan (GSI) with 50 m of grid resolution.
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