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model benchmarking. The memorandum recommends that, at a minimum, inundation models
should be examined by testing basic hydrodynamics and examining errors in mass conserva-
tion, and further describes 10 benchmark problems that should be used for model validation.
The benchmarking comprises analytical, laboratory, and ield data (e.g., comparisons to histori-
cal datasets of tsunami observations) with allowable error criteria of no more than 5 percent in
mass conservation, 5 percent or 10 percent in analytical and laboratory, and 20-25 percent in
the run-up accuracy for ield data. NTHMP participants agreed to use the Ofice of Oceanic and
Atmospheric Research (OAR) PMEL-135 for its benchmarking process, to share information,
and to develop a process for model validation. Although this process is a good start toward
achieving and maintaining quality control for different modeling practices performed by
NTHMP member states, the OAR PMEL-135 has not been used consistently in the production of
inundation maps among the states, and the outcomes have not been peer-reviewed. There-
fore, progress is dificult to assess, and it is not clear whether current maps sufice to plan safe
evacuations or prepare the public, given that they may have been produced with outdated
technology. Use of benchmarked models is undoubtedly needed for improved hazard assess-
ments and defensible evacuation and hazard maps.
Although the goal of the NTHMP MMS is to provide the guidance for accuracy and to
coordinate and standardize the mapping efforts as called for by Congress, this mechanism for
coordination has not resulted in more standardized maps. Coordination and standardization
of modeling approaches may prove to be dificult within the current MMS structure, given
the potential conlicts of interest of the state tsunami modelers that typically comprise the
subcommittee.
Because of the MMS dificulty in developing consistent mapping approaches or standards,
the committee discussed several options to reaching the goal of benchmarking models and
meet agreed upon standards. Instead of developing a standardized approach through the
MMS, the committee discussed the beneits of NOAA/PMEL providing the results of its hydro-
dynamic inundation modeling efforts to states. Because of the technical resources available at
PMEL, such an approach might provide the necessary consistency in modeling methodology
and input parameters across the states. This approach may also alleviate strains on state bud-
gets and the lack of inancial resources, which were cited by many NTHMP members as one of
the key challenges to making progress in producing the next generation of inundation maps.
This approach follows language in the 2006 Tsunami Warning and Education Act, which calls
for the NOAA Tsunami Program to provide “tsunami inundation models and maps for use in
increasing the preparedness of communities” (Section 4(b)(4)) and for NTHMP members to “use
inundation models that meet a standard of accuracy deined by the Administration (NOAA)
to improve the quality and extent of inundation mapping, including assessment of vulnerable
inner coastal and nearshore areas” (Section 5(c)(1)).
During the NTHMP meeting of 2008, the option of PMEL providing the inundation model-
ing was indeed discussed, and PMEL offered the modeling output, but states did not express
interest in using these results due to a lack in transparency regarding the choice of source
parameters. Given the somewhat unstable history of federal support and funding, states may
also be reluctant to rely on federally produced inundation efforts instead of in-house expertise
