HomeMy WebLinkAboutMulti-Hazard Mitigation Plan: 09. Tsunamis CIVIL DEFENSE AGENCY
COUNTY OF HAWAII
920 ULULANI STREET HILO,HAWAII 96720
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9. Tsunamis
Chapter 9:Hazard Analysis—Tsunamis
CHAPTER 9 - TSUNAMIS
9.1 Description of Hazard
A tsunami is a series of great waves most commonly caused by violent movement of the sea
floor, usually a fault resulting in an earthquake, but also caused by nearshore or underwater
landslides or volcanic eruptions. In contrast, regular ocean waves are generated from the
wind. Tsunami are characterized by exceptional speed(up to 590 mph), long wave length(up
to 120 miles), long period between successive crests (varying from 5 minutes to a few hours,
generally 10 to 60 minutes), and low height in the open sea. Often the first wave of a tsunami
may not be the largest. The danger from a tsunami can last for several hours after the arrival
of the first wave. Sometimes a tsunami causes the water near the shore to recede, exposing
the ocean floor. Tsunamis can be very large. At the shoreline, their height can be initially as
great as 30 feet or more (100 feet in extreme cases), and they can move inland several
hundred feet. Tsunamis can travel up rivers and streams that lead to the ocean.
The speed of onset depends upon whether the tsunami is a distant tsunami or a local tsunami.
Distant tsunamis result from earthquakes in Alaska, Japan, Chile, and other Pacific Rim loca-
tions (see Figure 9-1). A warning is almost certain and ranges from three hours to 12 hours.
Local tsunamis result from earthquakes or underwater landslides in the vicinity of the Hawai-
ian Islands, most frequently near the south coast of this island with the probability much
higher for the Ka'u-Puna districts than for South Kona. Adequate advance warning for local
tsunamis is not presently technologically possible. Therefore, the public must be educated
that the occurrence of strong ground shaking in a coastal area should be considered as a local
tsunami"warning"and an immediate coastal evacuation should follow.
9-1 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
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_ Map showing travel times(in hours)of tsunamis from the Pacific Ocean rim to Honolulu.The small stars indicate the
approximate points of origin of some tsunamis that have affected Hawaii.The origins of the disastrous tsunamis of 1946 and 1960 are
shown by the two larger stars.
Figure 9-1. Travel Times for Distant Tsunamis.
Source: Thomas,W."The Variety of Physical Environments among Pacific Islands,"in Man's Place in the Island
Ecosystem(ed.by F.R.Fosberg),Bishop Museum Press,1965.
9-2 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
9.2 Significant Historic Events
Tsunamis are infrequent events but can be extremely destructive. Since 1812, 25 tsunamis
have adversely impacted the Big Island. Of these, 22 were distant tsunamis and 3 were local
tsunamis(see Figure 9-2 for historical events and run-up heights).
Hawaii •,ter.. r w I twr a, drt•P In Ilw•IYn M W.
Tsunamis .
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Figure 9-2. Historic Tsunamis of Hawaii island
Source: Fletcher,C,B.Richmond,E.Grossman,A.Gibbs,Atlas of Natural Hazards in the Hawaiian Coastal Zone,
Prepared in cooperation with University of Hawaii,State of Hawaii Office of Planning,and National Oceanic and
Atmospheric Administration,U.S.Geological Service Geologic Investigations Series 1-2761,2002.
The most devastating tsunamis to hit the Island of Hawaii in this century occurred in 1946
and 1960. In both cases, the worst damage was inflicted on the northeastern coast of the
island. The tsunami of 1946 originated in the Aleutian Islands, struck Hawaii without
warning, and killed over 170 people, mainly at Laupahoehoe and Hilo where the wave
heights averaged 30 feet. The maximum wave height was 55 feet at Pololu Valley on the
northern tip of the island.
The 1960 tsunami originated in Chile and advanced upon the island from the southeast;
again, its effects were greatest at Hilo. The arrival time of this tsunami was correctly
predicted, but many people failed to heed the warnings, and authorities evacuated an
insufficient area of Hilo. As a result, 61 lives were lost as waves up to 35 feet high crashed
9-3 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
through homes. Whole city blocks were swept clean of all buildings, and 580 acres were
flooded. $23 Million in damages were reported.
The tsunamis of 1868 and 1975 were locally generated by earthquakes beneath the southern
coast of the island. The 1868 waves destroyed several coastal villages in the Ka'u and Puna
districts, most of which were never rebuilt. The 1975 tsunami claimed two lives and caused
widespread damage along the Kalapana coast.
Table 9-1. Tsunamis with Run-up of 2 meters or more:1812 to present
Maximum
height in
Hawaii
Deaths
1n
Date Place of observation Source Meters Feel in
Damage in Hawaii
1812:Dec.21 11 Hookena,Hawaii California 25 8 Hut flooded
1819:April 12 W.Hawaii Chile 20 7 Houses destroyed
1837:Nov.7 Hilo,Hawaii Chile 6.0 20 16 100 houses destroyed
1841:May 1T HIIO,HaWall Kamcnatka 4.6 15 - UI11(noWil
1860:Dec.1 Maliko Bay,Maui N.Pacific 2i 3.6 12 - Houses,wharf destroyed
1868:April 2 Keauhou Lancing,Hawaii Ka'u 13.7 45 47 Severe in Puna and Ka'u
1868:Aug.13 Hilo,Hawaii ChiJe 4.6 15 - Houses,bridges destroyed
1869:Aug.24 S.E.Puna S.Pack 2J 8.2 27 - Houses destroyed,roads washed out
1877:May 10 Hilo,Hawaii Chile 4.8 16 5 Severe in Hilo
1878:Jan.10 Mallko Bay,Maui N.Mololkal 21 3.6 12 - scattered flooding,N_Mail.N.Gahu
1896:June 15 Keauhou,Hawaii Japan 5.5 18 Houses,wharfs,stares destroyed
1903:Nov 29 Pelekunu.Molokai N.Molokai 4.5 15 Houses destroyed on Maui,
railroad washed out on Oahu
1906:Aug.17 Maalaea,Maui Chile 3.6 12 Piers damaged
1919:CU.2 Hoopuloa,Hawaii S.Kona 4.3 14 bWhan damaged,car swept away
1922=Nov.11 Hilo,Hawaii Chile 21 7 Fishing boats swept away
1923-Feb-3 Hilo,Hawaii Kamchatka 6.1 20 1 $1,500,ODD
1933:March 2 Keauhou,Hawaii Japan 3.2 10 - Boathouses,walls deAroyed in Kona
1946:April 1 Wailkolu valley,Molokai Aleulian Islands 16.4 54 159 $26.004,000
1952:Nov.4 Kaena,Oahu Kamchatka 9.1 30 - $1.000,000
1957:Marco 9 Haena,Kaual Aleullan Islands 16.1 53 - $5,000,040
1960:Plat+22 Hilo,Hawaii Chile 14.5 34 61 $23.000,000
1964:`larch 27 Waimea Bay,Oahu Alaska 4.9 16 - $68.000
1975:N-)v 29 Keauhou Landing,Hawaii S.Puna 14.3 47 2 $1.500,000
1' Earnest tsunami forwhich ckfiimte rnformationemsts.
2' Probable source_
Source- George Paaras-Cmayarmis.Carafog qf Tsrmamis in the HnurwPr n Fsiands (U.S.Coast an4'Geo&4ic Sm ey.May 1969):
Harold G.Loomis,Thv Inmaim gfNavember 29,075 pa Hmww (11auaiiListitute of Geophysics,December 1975),pp.1 and 10,
D.C.Cox avd L hiocganjocal Tsunands and PbmiNe local Tsunawrs in Hawarr (ELTvml1Im itute of Geophysics,Report HEG 77-14,
No=ber 1977);Doak C.Cox,Tsunami Casuaines and MonaLlly in Hrrtwn(University of Hamad,Euviravnamt Center,June 1987),
p.34,-James F.Lander Find Pattrcia A_Lockrid2e,UWW Stares Tspenauds(1nc1?dmg Unired-fares Possessions)1696LI988,
Publication 41-2,National Geophn sicalData Center,Aq"1989,pp.17-77,U_5.Geological Survey,Hawaiian Volcano Obwnatorv.
records;Pacific Tsunami l'e'arning Center,records
9-4 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
9.3 Probability of Occurrence
9.3.1.1 Distant Tsunamis
Distant tsunami events occur with a roughly 7% probability in a year. Events with smaller
waves have a higher probability than large waves (see Figure 9-3). Waves can strike all
coasts and persist up to several hours.
HBMTVS RECURRENCE PROBAB0.R %
MLO TSUNAMIS SINCE 1832;COX,CURTIS
30
7S t € +
j r I i i 1
1
LL p 0
15
_ w o o :
I
r
i
r 1 I
1 10 100
PR08AMMY,YEARS,RB01Hi UREATER IRAN
G7 OBSERVED 11Y,Y17�
Figure 9-3. Tsunami Height vs.Recurrence Probability for Hilo
9.3.1.2 Local Tsunami
Local tsunami events occur with a roughly 2%probability in a year. A local tsunami will be
of limited extent and duration. Near the seismic source, the waves may be 40 feet high but
have a short period and diminish rapidly, as demonstrated by the 1975 Halape tsunami
(Figure 9-4 shows the wave heights from the 1975 Halape tsunami as they traveled around
the coast to North Kona).
9-5 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
TSUNAMI WAVE HEIGHTS,
(Max.Wave)
20
South North
DISTANT
Combined historical distant tsunamis
15 h�
� I
w
LL i
= 10
� CAPT COOK
w
2
KEAHOLE
5
� 1975 LOCAL i
Southeast coast
0
45 So 55 80 as 70 75 80
COAST MILE
Figure 9-4. 1975 Halape Local Tsunami Wave Heights vs.Distant Tsunami
DATA FROM 1975 LOCAL TSUNAMI
Runup Height and Time vs Distance
50 25
45
4 V �
20
0
HEIGHT / TIME �/
RUNUP 35 \ \ TIME,
FEET 30 \ }� 15 MINUTES
25 \ //
20 \ 10
15i
10 x
5 /
0
0
80 60 40 20 5 0 2 20 40 60 80
DISTANCE FROM ORIGIN,MILES
Figure 9-5. Run-up height vs.time and distance,data from 1975 local tsunami
9.3.2 Hazard Areas
Two types of tsunami maps need to be distinguished: tsunami inundation and tsunami evacu-
ation maps. Tsunami inundation maps show the historical or calculated limits of inundation
in terms of the limits of inland inundation and the run-up height (for definition of terms, see
9-6 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
Figure 9-6).45 These inundation zones have been incorporated into the FIRM maps (V and
VE zones) and guide land use and construction standards. The tsunami evacuation zones are
derived from tsunami inundation maps, but are more conservative than the inundation snaps
in that they encompass a broader area that are potentially at risk that should be evacuated and
refer to readily identifiable physical landmarks such as roads where possible(see Figure 9-8).
On the one hand,these evacuation zones should not be so broad as to jam evacuation capabil-
ities; on the other hand,they should not be too narrow to risk injury or death.
NOTE R MAY BE GREATER OR LESS THAN h , DO NOT CONFUSE.
PRESENT WATER LEVEL/LINE MAY BE USED IN LIEU OF MSL, IF STATED.
MAX
MAX WATER LEVEL INTRUSION
—
-- ---—_ POINT
h=HEIGHT OF T
MEAN WAVE AT SHORELINE
SEA LEVEL I R=RUNUP HEIGHT
ABOVE MSL
MSL 1
INUNDATION LIMIT
Figure 9-6. Definition Sketch of Tsunami Inundation Terms
The evacuation zone map applies to distant tsunamis, assuming worst case wave action from
any probable source area. For local tsunamis, the arrival times are very short (typically min-
utes), and the felt earthquake is likely to be the only warning that many residents will receive
in advance of the first tsunami wave. Mitigation,therefore, depends primarily on public edu-
cation for a swift and appropriate response from within the coastal communities. A new sys-
tem is in place to alert police of a local tsunami generated from the southern coast of the
island. This system senses sea level rise at six locations on this southern shoreline.46 It alerts
the Pacific Tsunami Warning Center which immediately confirms the event by correlating it
to an earthquake signal and advises the County Civil Defense (or the police after working
hours). This system supplements the slower and less definitive earthquake-only local system
currently in service.
45 Historical data on tsunamis is primarily scattered run-up values. Hilo is unique in having well-documented
historical inundation lines for several tsunamis. Inundation for areas other than Hilo is the calculated"maxi-
mum expectable inundation".
46 Walker,Daniel,"Local Tsunami Real-time Warning System,"Science of Tsunami Hazards,v.20,n. 1,
2002.
9-7 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
NOR KOHA
HANIAKU
1
SOUTH KO
HANIAKUA,` t SOUTH HILO ; HILO
NoffnA NA SOUTH I H o
NORTHHILO
NORTH KO C� � � P A
KMIZI; .�
1
Kahl A
SOUTH KONA
H KONA KAU
Legend
-Tsunami Evacuation Zones
Major Road
\ Other Roads
i'
0 3 fi 72 78 24
Miles
Figure 9-7. Tsunami evacuation zones
Inset of Kailua-Kona Town
1
�4-
t
Tsunami Evacuation Area
Major Roads
Census Designated Places
Figure 9-8. Tsunami evacuation zones,Kailua-Kona zoom
9-8 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
9.3.2.1 Tsunami Inundation Zones
i -
on
st shore
3
..k�� � � • I• 1
ey
ion e.a as 7o es
Figure 9-9. Historical and Hypothetical tsunamis for inundation mapping
Figure 9-10. Updated tsunami evacuation zone map locations being developed
9-9 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
Coastal floodplain boundaries shown on the Flood Insurance Rate Maps (FIRM) for the
County of Hawaii are based on the 100-year Tsunami: wave elevation; runup elevations;
known topographic characteristics; and, a depth of flooding by the incoming Tsunami wave
of 4.0 feet. The 100-year Tsunami inundation boundaries were delineated using methods
outlined in "Tsunami Inundation Prediction," by C. L. Brentschneider and P. G. Wybro,
which was presented at the 15`x' International Conference on Coastal Engineering, Honolulu,
HI, in July 1976.
Since Hilo has one of the most complete historical inundation mappings, this data was
compared with the Preliminary DFIRMs to verify whether the VE zone encompassed the
furthest inland inundation limits. Surprisingly, the VE underzoned the historical inundation
(see Figure 9-11).
FEMA and the County are currently working to improve the Preliminary DFIRMS for the
County of Hawaii, which will include a careful evaluation of the coastal high hazard areas in
terms of combining the most protective inundation area from FEMA's 2008 Hurricane Flood
Study for Hawaii County(refer to Section 10.4.1.3) and the current effective FIRMs' coastal
high hazard areas.
Historical Inundation vs Evacuation Zone vs FIRM Legend
Study Area:Hilo [=IHiston-I nundation Zone streets
®FIRM 100 Year Entire area in Tsunami Evacuation Zone
Figure 9-11.Comparison of Historical Tsunami Inundation to FIRM VE Zone for Hilo
9-10 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
9.3.2.2 Evacuation Zone Maps
Hawaii was the first state to develop tsunami evacuation maps. The tsunami evacuation
maps were created in 1989-91 using one-dimensional numerical models.47 This approach
used historical inundation records to infer the nearshore tsunami heights, which in turn
provide the inundation limits through repeated calculations at transects perpendicular to the
adjacent coastlines. However, the original inundation maps for Hawaii data on which these
were based are no longer available. Technical advances enable a more rigorous approach
using a two-dimensional model. The results of the 2-D model indicate that the existing
evacuation lines may need to be moved further inland in certain areas. Additionally, the 2-D
model could better define inland waterway embankment inundation which was not addressed
by the 1-D model. However, because of the extensive cost to remap the entire evacuation
zone, remapping is prioritized to recent coastal developments and densely populated areas. A
new generation of tsunami evacuation zone maps is being prepared in 2009-2010, based on
2-D inundation modeling by the University of Hawaii, School of Ocean and Earth Science
and Technology(UH SOSET).
The analysis uses 2-dimensional modeling with updated bathymetry and topographical data
utilizing recent LIDAR topographical surveys, which provide a higher resolution of the
shallow reef forms below sea level and shoreline above sea-level than previously available.
The National Tsunami Hazard Mitigation Program requires 2D numerical modeling and
credible worse-case scenarios when mapping tsunamis affecting Alaska, California,
Washington, Oregon, and Hawaii. The tsunami inundation and runup analysis performed by
UH SOSET uses scenarios from tsunami-genic source regions along the Pacific Rim, see
Figure 9-9. The methodology to meet this standard essentially uses the same 5 historical
events (4 from Aleutian and one from Chile) used by the original tsunami map, but uses 2D
methodology; also added hypothetical events assumed to be 2X the Great Sumatra Tsunami
(beyond credible magnitudes), from other directions (west, e.g., Japan, and south Pacific,
e.g., Marianas, and East Pacific, e.g., Cascadia), to test the model results. The hypothetical
events do not appear to generate greater inundation than the historical suite of events due to
directionality effects in the wave propagation. The 2-D modeling has been validated as
producing good results when hindcasting historical inundation and runup data. The analysis
has provided updated inundation zones around the island at locations indicated in Figure
9-10. Evacuation maps are soon to be updated in 2010 based on the results of this analysis.
The inundation and run-up analysis is based on scenarios not on statistical probabilistic
methods. An improved analysis would develop "Maximum credible inundation" maps based
on probabilistic estimation. At some point, building code maps will need to incorporate
tsunami inundation. Building designers need the tsunami inundation data to properly site and
design structures against tsunami forces.
9.4 Risk Assessment
Similar to the coastal flooding hazard an annualized loss can be estimated based on the
exposure and the probabilistic tsunami inundation.
47 Curtis,George,D.,Hawaii Inundation/Evacuation Map Project,Final Report,Joint Institute for Marine and
Atmospheric Research,University of Hawaii,April 1991.
9-11 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
To describe tsunami-prone landscapes and community vulnerability to tsunamis on the
Hawaiian coast, (USGS Scientific Investigations Report 2007-5208) used geographic-
information-system (GIS) tools and publicly available geospatial data to create spatial
overlays of hazard and socioeconomic data. Details on each of the socioeconomic datasets
used in this analysis follow an overview of our analytical approach and the study area.
Vulnerability calculations and comparisons are limited to the exposure and sensitivity of the
urban footprint and certain assets, including developed land, populations (residential,
employee, and tourists), economic assets and critical facilities. Exposure is defined as the
amount of an asset (for example, the number of residents of a town) within a tsunami
evacuation zone.
Based on a spatial overlay of CDP (Census Designated Places) and tsunami-evacuation-zone
data, there are 65 CDPs (hereafter called communities) in the State of Hawaii that contain
tsunami-prone land. 13 of these are located in Hawaii County, these are shown in Figure
9-12.
C otuity of Hawaii { xalu'ul.a
1 Kukuihacle
Dmpahoehoe
Puak5
Kalaoa Hilo
Hax•aiian
KAjJ na N H a w i L 1 Paradise Park
' 1 Hawaiian
Holuuloa Beaches
Kahnlu'u-Keauhou
Captain Cook
Mnamma-Napo op`o
r
T Nonh Pacific Oreav
0 10 iOM
w
Figure 9-12.Tsunami prone communities in the County of Hawaii
To determine the number and type of residents in the tsunami-evacuation zones, USGS used
block-level population counts and demographic data from the 2000 U.S. Census (U.S.
Bureau of Census, 2001). Tax base is represented by current parcel values and is considered
an attribute of community vulnerability because communities rely on property taxes for local
services. Results of the GIS-based analysis are summarized by tsunami-evacuation zone and
by CDP-based community. Figures summarizing these results are included below.
9-12 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
Aaruu1 off 0 0.8.73 Fe[oeomgeof 75-LOOT
Developod Laud 0 p,4-0.7g AewLop2dLaud 6 SR-7455
m Tsunami- O 0.l-039 AT�ujiam- 6 25-49%
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9-13 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
TcteLPhmdVelu 4516M-4-9E Pe"n4eoff 75-1009,
IL&6M-5 AM 'lbtal l'BM Value O 70-74%
LmuSLUe mphonc] 334M-IMM (raiowoD? pdons)in c 25-49%
in 7suoeoii- o IL-04K Tzuoomd-U�uadan o 1-'A4'
Evacuation Zone 0 pone 0%
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un �0
ra.
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Figure 9-13.Results of USGS tsunami vulnerability study
9.5 Mitigation Strategies
9.5.1 Previous/Current Efforts
9.5.1.1 Deep-ocean Assessnient and Reporting of Tsunainis (DART)
When a tsunami event occurs, the first information available about the source of the tsunami
is based only on the available seismic information for the earthquake event. As the tsunami
wave propagates across the ocean and successively reaches the DART systems, these
systems report sea level information measurements back to the Tsunami Warning Centers,
where the information is processed to produce a new and more refined estimate of the
tsunami source. The result is an increasingly accurate forecast of the tsunami that can be used
to issue watches,warnings or evacuations.
Over the past 20 years, NOAA's Pacific Marine Environmental Laboratory (PMEL) has
identified the requirements of the tsunami measurement system through evolution in both
technology and knowledge of deep ocean tsunami dynamics. The tsunami forecasting
technology developed at PMEL is based on the integration of realtime measurements and
modeling technologies, a well-tested approach used in most hazard forecast systems.
Developed by PMEL and deployed operationally by NOAA's National Data Buoy Center
(NDBC), DART is essential to fulfilling NOAA's national responsibility for tsunami hazard
mitigation and warnings.
Design: The first-generation DART design featured an automatic detection and reporting
algorithm triggered by a threshold wave-height value. The DART II design incorporated two-
way communications that enables tsunami data transmission on demand, independently of
the automatic algorithm; this capability ensures the measurement and reporting of tsunamis
with amplitude below the auto-reporting threshold.
9-14 Hawaii County Multi-Hazard Mitigation Plan
Chapter 9:Hazard Analysis—Tsunamis
;C 75 N
Station Ovurers
• NDBC DART
Australia
1-4
o Chile 4
• Indonesia r ` ,-- .. T /F140 N
Thailand
a • a •aa +
� i • � �� 46 N
30 N
R • • i � � ' 15 N
E 457:
- 0
fyny�9� a
— — `►J� .a f � 30 S
40 E 80 E 80 E 900E 120 E 140E 980E 980 180 W 140 w 120 w 100 w 80 w 80 w 40 w 20 w 0 POE
Figure 9-14. Locations of DART buoys
9.5.1.2 Tsunami Inundation Run-up Mapping
A tsunami inundation and run-up analysis of the islands of Oahu and Hawaii was performed
though the University of Hawaii, school of Ocean and Earth Science and Technology using
scenarios from tsunami-genic source regions along the Pacific Rim. The analysis uses 2-
dimensional modeling with updated topographical data utilizing recent LIDAR topographical
surveys that provide a higher resolution of the shallow reef forms below sea level and
shoreline above sea-level than previously available. The 2-D modeling has been validated as
producing good results. The analysis has provided updated inundation zones around the
island. Evacuation maps are soon to be updated based on the results of this analysis.
The inundation and run-up analysis is based on scenarios not on statistical probabilistic
methods. An improved analysis would develop "Maximum credible inundation"maps based
on probabilistic data, although there is currently not sufficient historical tsunami data to
develop such maps.
9.5.1.3 Perfbrmance Based Tsunami Engineering
An experimental program by the University of Hawaii, Oregon State University and
Princeton University is close to being concluded, having investigated tsunami bore
formation, impact on structures, inundation and scouring. Design provisions for the
structures located in inundation zones are currently being developed using the results of these
studies. It is anticipated that there will be two design methodologies: a prescriptive
methodology with a predefined water height and water velocity to characterize the tsunami
hazard; and a site specific analysis method using calibrated analysis tools to determine the
local tsunami inundation characteristics.
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Chapter 9:Hazard Analysis—Tsunamis
9.5.2 Future Plans
Project Description Status
Update tsunami evacuation neaps: The 2-D model is based on good Ongoing project: Any necessary
Tsunami Inundation and Runup topographic data along the coastline evacuation zone changes would be
Mapping: Analysis of the island of (e.g.,LIDAR)."Maximum credible done by Quince Mento of HCDA
Hawaii based on scenarios from inundation"used to develop evacuation based on updated information from
tsunami-genic source regions along maps UH SOEST
the Pacific Rim. Big Island mapping
focuses on 12 populated areas around
the island.
It was originally thought that the 2-D The present maps have historical tsunami Proposed Planning Project: There will
modeled tsunami inundation maps inundation embedded,but the new need to be DFIRM modifications to
would be incorporated into the FIRM DFIRMs do not. FEMA is addressing the Flood Maps if tsunami inundation
maps as the VE zone. However, this issue in 2010 with a supplemental is to be any factor in zoning and
FEMA originally determined the study to compare the differences construction requirements.
Tsunami based coastal floodplain between the existing and new DFIRM Phase I: The DFIRM will be based on
boundaries for the nation using a 1-D maps,and to produce maps using the the most protective of FEMA's 2008
model.Conceivably,FEMA will greater effect along the south and west hurricane study boundaries and the
determine future changes to the coasts. current FIRM's coastal floodplain
Tsunami based coastal floodplain boundary.The northeast coastline will
boundaries using a 2-D model.The continue to reflect the current FIRM's
DFIRM will include the most coastal floodplain boundary,which is
protective ofFEMA's 2008 hurricane based on Tsunami indundation.
study boundaries(refer to Section Phase II: UHM SOEST mapping(by
10.4.1.3)and the current FIRM Kwok Fai Cheung)can produce 100-
coastal flood boundary. year and 500-year probabilistic
tsunami hazard maps to provide future
local modifications to the DFIRMs.
Tsunami design guidelines for Update of the design provisions for Under development by University of
buildings Sept 2010 guidelines for tsunami bore impact and Hawaii at Manua,Princeton,OSU,
new and for evaluating existing inundation/scouring and Martin&Chock;for future
buildings. adoption
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