Dynamics and Vulnerability of Delta Systems - loicz

Deltas are probably as susceptible to coastal storms as to the previously discussed river floods.
Hurricanes can produce storm surges over 10m, and that does not include the waves carried by
the surges. It is the storm surge that allows breaking waves to move inland and which is
responsible for most deaths in deltaic regions. Figure 2.3 provides an example of the storm tracks
of historical hurricanes.
Type Category Winds (knts) Surge (m)
Depression TD < 34 -
Tropical Storm TS 34-39 -
Hurricane 1 64-82 1.2-1.5
Hurricane 2 83-95 1.8-2.4
Hurricane 3 96-113 2.7-3.7
Hurricane 4 114-135 4.0-5.5
Hurricane 5 >135 > 5.5
Fig. 2.3: The Saffir-Simpson Scale of hurricane intensity and expected surge height (from Unisys Weather
Service http://weather.unisys.com/hurricane/index.html), and better- known deltas (red stars) superimposed on
storm track map.
There is little question that the number of North Atlantic hurricanes increased significantly since
the 1850’s and even more markedly since 1980 (Webster et al. 2005, Holland & Webster 2007)
along with observed increasing sea surface temperature. Importantly, the destructive potential of
these storms has increased as well. Data of the other main oceans is more ambiguous.
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