organic matter input. If vertical accretion equals sea-level rise, the coastal
wetland will grow upwards in place. However, if accretion is less than sea-level
rise, the coastal wetland steadily loses elevation relative to sea level. Vegetated
wetlands are submerged for progressively longer periods during the tidal cycle
and may die due to water-logging, causing a change to bare sediment, or even
open water. Unvegetated intertidal areas are just progressively submerged.
Therefore, coastal wetlands show a dynamic and non-linear response to sea-level
rise.
Direct losses of coastal wetland due to submergence (or edge erosion) can be
offset by inland wetland migration (coastal dryland conversion to wetland). As
sea level rises, so some low-lying coastal areas become suitable for the growth of
wetland plants. In areas without low-lying coastal areas, or in low-lying areas
that are protected by humans to reduce coastal flooding, wetland migration
cannot occur. This produces what is termed a ‘coastal squeeze’ between the
defences and rising sea levels. Therefore, adaptation to protect human use of
the coastal zone may exacerbate wetland losses.
Coastal erosion. Bruun suggested that there was a link between sea-level rise
and shoreline recession on sandy beaches based on an equilibrium model of
cross-shore beach response. On a typical beach, this might result in shoreline
recession 100 times the rise in sea level. The Bruun Rule excites great passion and
while there are several field studies that suggest it has some validity — the
concept remains controversial. Importantly, the Bruun Rule only describes one
of many processes shaping sandy coasts. An additional erosional process linked
to sea-level rise is the indirect effect of sea-level rise: as seas rise, estuaries and
lagoons maintain equilibrium by raising their bed elevation in tandem, and act as
a major sink for sand. The sand is eroded from the open coast, potentially
D. R. Cahoon, D. J. Reed and J. W. Day, Jr., Estimating shallow subsidence in microtidal
saltmarshes of the southeastern United States: Kaye and Barghoorn revisited, Marine Geol., 1995,
128, 1—9.
D. R. Cahoon and J. C. Lynch, Vertical accretion and shallow subsidence in a mangrove forest of
southwestern Florida, U.S.A., Mangroves Salt Marshes, 1999, 1, 173—186.
R. J. Nicholls, Coastal zones, in M. L. Parry (ed.), Assessment of the Potential Effects of Climate
Change in Europe, Jackson Environment Institute, University of East Anglia, 2000, pp. 243—259.
P. Bruun, Sea level rise as a cause of shore erosion, J. Waterways Harbors Div., ASCE, 1962, 88,
117—130.
E. B. Hands, The Great Lakes as a test model for profile responses to sea level changes, in P. D.
Komar (ed.), Handbook of Coastal Processes and Erosion, CRC Press, Boca Raton, FL, 1983, pp.
167—189.
N. Mimura and H. Nobuoka, Verification of the Bruun Rule for the estimation of shoreline retreat
caused by sea-level rise, Proceedings of Coastal Dynamics 95, Gdansk, Poland, 4—8 Sept. 1995,
ASCE, New York, 1996, pp. 607—616.
S. P. Leatherman, K. Zhang and B. C. Douglas, Sea level rise shown to drive coastal erosion, EOS
(Trans. Am. Geophys. Union), 2000, 81 (6), 55—57.
P. D. Komar, Beach and Nearshore Sedimentation, Second Edition, Prentice Hall, Upper Saddle
River, NJ, USA, 1998.
M. A. Van Goor, M. J. F. Stive, Z. B. Wang and T. J. Zitman, Influence of relative sea level rise on
coastal inlets and tidal basins, Proceedings of Coastal Dynamics 2001, ASCE, New York, 2001, pp.
242—251.
Rising Sea Levels: Potential Impacts and Responses
95
wetland will grow upwards in place. However, if accretion is less than sea-level
rise, the coastal wetland steadily loses elevation relative to sea level. Vegetated
wetlands are submerged for progressively longer periods during the tidal cycle
and may die due to water-logging, causing a change to bare sediment, or even
open water. Unvegetated intertidal areas are just progressively submerged.
Therefore, coastal wetlands show a dynamic and non-linear response to sea-level
rise.
Direct losses of coastal wetland due to submergence (or edge erosion) can be
offset by inland wetland migration (coastal dryland conversion to wetland). As
sea level rises, so some low-lying coastal areas become suitable for the growth of
wetland plants. In areas without low-lying coastal areas, or in low-lying areas
that are protected by humans to reduce coastal flooding, wetland migration
cannot occur. This produces what is termed a ‘coastal squeeze’ between the
defences and rising sea levels. Therefore, adaptation to protect human use of
the coastal zone may exacerbate wetland losses.
Coastal erosion. Bruun suggested that there was a link between sea-level rise
and shoreline recession on sandy beaches based on an equilibrium model of
cross-shore beach response. On a typical beach, this might result in shoreline
recession 100 times the rise in sea level. The Bruun Rule excites great passion and
while there are several field studies that suggest it has some validity — the
concept remains controversial. Importantly, the Bruun Rule only describes one
of many processes shaping sandy coasts. An additional erosional process linked
to sea-level rise is the indirect effect of sea-level rise: as seas rise, estuaries and
lagoons maintain equilibrium by raising their bed elevation in tandem, and act as
a major sink for sand. The sand is eroded from the open coast, potentially
D. R. Cahoon, D. J. Reed and J. W. Day, Jr., Estimating shallow subsidence in microtidal
saltmarshes of the southeastern United States: Kaye and Barghoorn revisited, Marine Geol., 1995,
128, 1—9.
D. R. Cahoon and J. C. Lynch, Vertical accretion and shallow subsidence in a mangrove forest of
southwestern Florida, U.S.A., Mangroves Salt Marshes, 1999, 1, 173—186.
R. J. Nicholls, Coastal zones, in M. L. Parry (ed.), Assessment of the Potential Effects of Climate
Change in Europe, Jackson Environment Institute, University of East Anglia, 2000, pp. 243—259.
P. Bruun, Sea level rise as a cause of shore erosion, J. Waterways Harbors Div., ASCE, 1962, 88,
117—130.
E. B. Hands, The Great Lakes as a test model for profile responses to sea level changes, in P. D.
Komar (ed.), Handbook of Coastal Processes and Erosion, CRC Press, Boca Raton, FL, 1983, pp.
167—189.
N. Mimura and H. Nobuoka, Verification of the Bruun Rule for the estimation of shoreline retreat
caused by sea-level rise, Proceedings of Coastal Dynamics 95, Gdansk, Poland, 4—8 Sept. 1995,
ASCE, New York, 1996, pp. 607—616.
S. P. Leatherman, K. Zhang and B. C. Douglas, Sea level rise shown to drive coastal erosion, EOS
(Trans. Am. Geophys. Union), 2000, 81 (6), 55—57.
P. D. Komar, Beach and Nearshore Sedimentation, Second Edition, Prentice Hall, Upper Saddle
River, NJ, USA, 1998.
M. A. Van Goor, M. J. F. Stive, Z. B. Wang and T. J. Zitman, Influence of relative sea level rise on
coastal inlets and tidal basins, Proceedings of Coastal Dynamics 2001, ASCE, New York, 2001, pp.
242—251.
Rising Sea Levels: Potential Impacts and Responses
95