NHR3 Tsunami Portal FAQ

What datum was the shoreline boundary (e.g., MHW, NAVD88)?

• MHW

Can the output layers be downloaded in an ArcGIS-compatible file format?

• The coordinates of the Transects are given at the very end of the EGL-Run output in the Optional Output Section

Was there subsidence information on the output?

• There is not subsidence data in the output. We may add it as we make upgrades

Is the topography/bathymetry (NAVD-88 vertical datum) used for  inundation calculation came from NOAA?  Is the resolution of the NOAA topography/bathymetry for a particular site disclosed somewhere in the result page?   The resolution of NOAA dataset for topography/bathymetry appears to range from 1 meter to 10 meters.  Because flow elevation is given in the tsunami inundation results, I am curious whether flow depth (instead of flow elevation) is more accurate representation of the calculated outcome.  Any suggestions? Thanks

• The vertical datum used in the web portal is mean high water (MHW)...not NAVD88. To convert to NAVD88 you should go to the NOAA website and find the nearest tidal station to your site. The NOAA site provides both MHW and NAVD88 so you can adjust the web portal results. (Here is a link for the LA station: https://tidesandcurrents.noaa.gov/datums.html?id=9410660).

• You will also need to add in some wave height to account for sea level rise. Caltrans has a STP (20.13) that gives recommended values.

• Regarding flow depth vs elevation, we used ground elevations from the tsunami inundation model plus flow depth to get the flow elevation (so everything is consistent.) My experience is that the spatial variability of flow elevation is much less than flow depth since flow depth is strongly influenced by ground elevation. (Water smooths out small scale topographic variation.)