Storm surges the case of Hamburg, Germany

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Storm surges the case of Hamburg, Germany

• Hans von Storch
• Institute for Coastal ResearchGKSS Research
  Center, Geesthacht

Parallel 26 Global environmental change, natural
disasters, and their implications for human
security in coastal areas, 11. November 2006
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Storm surges the case of Hamburg, Germany Hans
von Storch, Werner Krauss, Martin Döring and Iris
Grossmann Along the coast of the North Sea,
storm surges present the major geophysical risk.
A long history of disaster has engraved the
severity of this danger deeply into the cultural
texture of the local population. While the
situation has not much changed in rural regions,
the situation has changed significantly in
Hamburg, which is connected to the North Sea by
the Elbe estuary. Here, the risk, and the
vulnerability of the population has changed quite
a bit. The geophysical risk has changed by more
efficient coastal defence measures as well as a
repeated deepening of the shipping channel.
Climate change has played a very minor role so
far, but may become more important after 2050, or
so. The vulnerability of the population has
increased as well. The effective coastal defence
has created a perception of absolute security,
even if scientists have demonstrated that a
slight modification of past storms (in terms of
path, and speed) could cause dangerously high
storm surges. The vulnerability has also
increased because of the influx of people not
originating from the coastal zone, who simply are
not aware of the severity of the risk. We
discuss this multi-faceted situation as a case
study, which features geophysical risks, globally
and regionally induced changes related to
globalisation, changing populations
(urbanization) and alarmist claims on climate
change. A brief comparison of the public
perception of the Katrina disaster is included in
the discussion.
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Historically, the coast was a place of danger
(and some opportunities) for humans. The first
priority was to defend against storm surges. Life
was adapted to this risk.
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Nowadays, people consider themselves safe from
the dangers of the sea, and are concerned about
the health and the opportunities related to the
coastal seas.
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Hamburg storm surges
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In the early 90s, the specter of Global Warming
entered the perception of people. Storm got
worse.
Proxy for storm activity in the North Sea region
(after Alexandersson, SMHI, 2003)

• Scientists related worsening of storm climate to
  GHG emissions (warmer world gt more water vapor gt
  more energy for storms gt situation will continue
  to worsening).
• Insurance companies supported the claims.
• Media took up the message, which is consistent
  with cultural pre-conception of humans changing
  climate to become worse.
• Nowadays widely accepted among media and
  lay-people that storms are getting worse.
  However, the claim is false.

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Proxy for storm activity in the North Sea region
(after Alexandersson, SMHI, 2003)
Bärring, 2005 blue - Lund red Stockholm
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Where does the enhanced storm surge levels
Hamburg come from?

• Sea level rise a few centimeters
• Intensification of storm activity 1960-1995
• What else has happened in the coastal/estuarine
  environment?

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Difference in storm surge heights mouth of Elbe
estuary and Hamburg, 1900- 2005
The tidal change is due to coastal protection
measures and modifications of the tributaries,
and to the deepening of the shipping channel.
These measure also had an effect on the heights
of severe storm surges estimates are 45 cm
caused by measures of coastal defense and 15 cm
by deepening the shipping channel (Haake, 2004
27).
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• Thus, so far, global warming had no discernible
  impact on the storm surge risk in Hamburg.
• Will it have an effect?

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Regional and lcoal effect of expected
anthropogenic climate change (A2 and B2)
Model of North Sea hydrodynamics
Katja Woth
Global scenario
Dynamical Downscaling
Tide gauge St. Pauli
Empirical localization
Joint work with regional authorities.
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Scenarios 2030, 2085
Only the effect of anthropogenic climate change
(A2, B2) - No effect of water works.
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Conclusions

• For storm surge risk in Hamburg, modifications of
  the estuary are presently more important than
  anthropogenic climate change in the distant
  future they may be of comparable significance.
• Public perception is changing to Storm surge
  risk is mostly related to GHG emissions. Thus
  storm surge risk can be controlled by regulating
  these emissions.
• Vulnerability enhanced by framing storm surge
  risk as GHG problem and not as natural hazard
  exaggerated by regional modifications.
• Sloppy talking about Global Warming has
  detrimental effect on better adaptation.
• The same true for Hurricane hazard?