The Grand Challenges for Disaster Reduction

The
Grand Challenges for Disaster Reduction outlines a ten-year
strategy crafted by the National Science and Technology Council’s
Subcommittee on Disaster Reduction (SDR). It sets forth six Grand
Challenges that, when addressed, will enhance community
resilience to disasters and thus create a more disaster-resilient
Nation. These Grand Challenges require sustained Federal
investment as well as collaborations with state and local
governments, professional societies and trade associations, the
private sector, academia, and the international community to
successfully transfer disaster reduction science and technology
into common use.
To meet these Challenges, the SDR has identifi ed priority
science and technology interagency implementation actions
by hazard that build upon ongoing efforts. Addressing these implementation actions will
improve America’s capacity to prevent and recover from disasters, thus fulfi lling our
Nation’s commitment to reducing the impacts of all hazards and enhancing the safety
and economic well-being of every individual and community. This is the tsunami-specifi c
implementation plan. See also sdr.gov for other hazard-specifi c implementation plans.
What is at Stake?
DEFINITION AND BACKGROUND. Tsunamis—large, rapidly
moving ocean waves resulting from disturbances on the ocean
fl oor—are among the most devastating of all hazards. United
States coastal communities are threatened by tsunamis generated
by both local and distant sources.
IMPACTS. The Great Alaskan Earthquake and Tsunami was one
of the most disastrous seismic events in United States history.
The event began when the largest earthquake in North American
history struck the Alaskan coast on March 28, 1964. The
earthquake caused 115 deaths, 106 of which were the result of tsunamis generated by the
quake. Five tsunami waves impacted the United States Pacifi c Coast from Alaska to
California and Canada, resulting in $84 million in damages.1
Local tsunamis give residents only a few minutes to seek safety. Tsunamis of distant
origin give residents more time to evacuate the threatened coastal areas, but require
timely and accurate tsunami forecasts of the hazard to assure proper response and to
avoid costly false alarms. For example, residents of Alaska can experience either a local
earthquake and local tsunami or tsunamis of distant origin, while residents of Hawaii and
the west coast generally experience hazards from distant tsunamis. The 1946 tsunami,
which was the most devastating in Hawaiian history, originated in the Aleutian Islands,
but resulted in waves of up to 17 meters (55 feet) in height striking Hawaii. This event
ultimately resulted in 170 deaths and permanent damage to the city of Hilo.2
Similarly, Pacifi c Northwest residents can experience a local tsunami that also may have
an impact on the distant states of Alaska and Hawaii. A tsunami in the Caribbean could
result in a local tsunami for Puerto Rico that also impacts Atlantic coast communities in
the Southeast as a distant tsunami. Of the two, local tsunamis can pose a greater threat to
life because of the short time between generation and impact.
The Indian Ocean tsunami of December 26, 2004 gave rise to levels of loss and grief
unprecedented in the history of natural hazards in the region. The massive impact was
due to a lack of public awareness, effective warning systems, and implemen tation of
mitigation measures. For example, rapid evacuation to inland areas would have saved
many lives. Recognizing the complexity and scope of the sustained efforts needed to
ensure tsunami risk reduction in the decades to come, hazard assessment, accurate
warnings, response planning, and new or improved actions in public awareness,
mitigation, and research are needed. All of these efforts require sustained coordination,
attention, and support on the Federal, state, and local level. The National Science and
Technology Council’s 2005 report, Tsunami Risk Reduction for the United States: A
Framework for Action, calls on the National Tsunami Hazard Mitigation Program, a
Federal-state partnership led by NOAA, to “develop, coordinate and sustain an effective
and effi cient tsunami risk reduction effort in the United States over the long term.”

17.16 | Posted in , | Read More »

RECOVERY OR LONG TERM EFFECTS ON COASTAL GROUNDWATER SYSTEMS?

As time passes, the saltwater that has infiltrated, through the soil surface or from water bodies and wells,
moves through the groundwater in a general downward and lateral direction towards the coast (or maybe
towards a lagoon or inland water body). Eventually, and with a continued influx of rainwater, the saltwater
will be suppressed, mixed, diluted and transported to the open water. These are natural processes that
occur and allow that over the longer term, the aquifer can recover and return fresh.
9
The International Groundwater Assessment Centre (IGRAC) made some preliminary estimations of the
time required to naturally rehabilitate the coastal aquifers3. Using a numerical simulation model and applying
some simplifying assumptions of the land-groundwater system it was estimated that it would require a
couple of years to obtain pre-tsunami salt concentrations in the aquifer, under conditions prevailing in the
Maldives, which is an archipelago to the west of Sri Lanka, also impacted by the tsunami. Some of the
uncertainties associated with this simulation are related to:
1. Insufficient knowledge of actual conditions. Some of the factors/parameters that have not been
assessed based on actual conditions and measurements, and may significantly influence the results
are:
• The hydraulic conductivity of the aquifer, which determines the rate at which water moves through
the sediments
• The depth of the aquifers, i.e. if there is an impermeable layer restricting the freshwater lens
• The influence of actual rainfall occurring in the affected areas
• The amounts and patterns of pumping
2. Furthermore, some important processes/phenomena may not have been incorporated sufficiently:
• The infiltration from stagnant water bodies has not been included
• The possible disruption of the freshwater lens due to an underground pressure wave has not been
included
• The possible slow leaching of the saltwater in the aquifer due to low permeable zones, or so-called
double-porosity characteristics

17.13 | Posted in , , , | Read More »

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