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HR: 16:45h
AN: G44A-04 INVITED
TI: On the use of Local Sea Level Scenarios for Managing and Mitigating the Impact of Coastal Inundation
AU: * Plag, H
EM: hpplag@unr.edu
AF: Nevada Bureau of Mines and Geology and Seismological Laboratory, University of Nevada,
Reno, Mail Stop 178, Reno, NV 89557, United States
AU: Hammond, W C
EM: whammond@unr.edu
AF: Nevada Bureau of Mines and Geology and Seismological Laboratory, University of Nevada,
Reno, Mail Stop 178, Reno, NV 89557, United States
AB:
Coastal inundation is increasingly recognized at national and international levels as an issue with potentially
extreme societal impact. Consequently, there is an urgent need for decision-support tools that would help to
manage and mitigate the impacts of coastal inundation, storm surges, and human activities on coastal
communities and ecosystems.
Decision making with respect to mitigation in the coastal zone is an extremely complicated issue for various
reasons, including but not limited to: (i) The time scales involved are long from a human perspective, with coastal
engineering typically dealing with infrastructure with a life time of 50 to 200 years. (ii) The economic scale of the
problem is extreme: For example, the costs for increasing the height of the coastal dikes in Germany by 1 m are
estimated to be of the order of 300 billion Euro; the flood gates being built in Venice are an estimated 5 billion
Euro. The scale of the required investments is often seen as prohibitive for precautionary action without solid
scientific basis, and failing to invest where needed may lead to large economic losses as demonstrated in New
Orleans. (iii) Coastal zones are a magnet for human activities (one could say that society tends to put its "jewelry"
in the coastal zone): the main increase in vulnerability in the coastal zone is not expected to come from increased
hazards due to climate change but rather from increased risks due to continuing migration of population into the
coastal zone and an associated increase in key infrastructure.
Decisions on mitigation and adaptation in the coastal zone are likely to affect the life and prosperity of people in
the future. Reliable and precise predictions of coastal inundation risks, for example through local sea level rise,
would be invaluable for decision support. However, considering the aleatory and epistemic uncertainties in the
processes that contribute to the hazards and risks in coastal zones over the 50 to 100 year time scale, accurate
predictions cannot be made. What can be provided at best are reasonable scenarios, which describe a set of
plausible trajectories based on the best information available about the present trends and specific assumptions
about future evolution of the system. Scenarios thus give a better indication of the range of plausible futures than
analyses based solely on aleatory uncertainty of present trends. Unfortunately, applying this approach to the
coastal zone often emphasizes the large uncertainties and wide range of plausible futures (particularly if a
realistic variety of assumptions is considered).
We have developed an observation-based approach to scenarios for future local sea levels which allows us to
consider a wide range of assumptions concerning the main contributions (vertical land motion, steric changes in
the ocean volume, atmospheric circulation changes, and ocean-ice mass exchange) and thus to assess the full
range of plausible futures a given location might be facing, including the associated uncertainties. We will
demonstrate the approach for three example locations (Venice, New Orleans, Boston) and discuss the relative
weight of the uncertainties in the forcing factors at these locations. Communicating the range of plausible futures
and the uncertainties to decision makers in a proper way is a key problem that we as scientists too often tend to
ignore.
DE: 0726 Ice sheets
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1630 Impacts of global change (1225)
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Geodesy [G]
MN: 2007 Fall Meeting
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