Download Climate change: impact on coasts and estuaries

Climate change: impact on coasts and estuaries
by Michael Collins
Emeritus Professor
School of Ocean and Earth Science
University of Southampton
National Oceanography Centre
Southampton, U.K.
[Abstract]
Coasts are energetic sedimentary environments; they form part of a sedimentary system,
which extends from catchment headwaters to the deep ocean. Throughout geological time,
relative sea level changes have ensured that beaches and estuaries occupied different
areas of the continental margins. In addition to natural changes, parts of the system can
be influenced by man-made impacts. Examples are the damming of rivers and/or the
installation of coastal defence structures.
Within the context of processes taking place at various spatial and temporal scales,
climate-related ocean-atmosphere oscillations (e.g., ENSO and NAO) occur. Climate
change can be identified if variability in properties persists over an extended period,
typically decades or longer. Interestingly, wave height variability has been correlated
with variations in the NAO. Various scenarios have been considered by IPCC, in relation
to projections of future changes in sea level (1990 to 2100).
The potential impacts of climate change and sea level rise, on coastal systems, have been
considered by a wide range of scientists and coastal engineers. Such consequences
include, amongst others: coastal erosion; and changes in wind patterns and storms; and
changes in wave patterns and extreme events. The IPCC Fourth Assessment Report
relates to predictions of ‘very high confidence’ and ‘high confidence’. Inundation of the
coastline is predicted on the basis of the ‘Bruun Rule’, relating to beach translation.
Estuaries are complex systems, which react strongly to modifications of either the
surrounding basin or the adjacent sea. Estuarine roll over, together with sea level rise in
estuaries can result in sediment infilling and, eventually, sediment expulsion.
1
An approach to the problem of the prediction of the impact of climate change/ sea level
rise is through the use of a Coastal Vulnerability Index (CVI). Such an approach has been
applied to locations in the Mediterranean Sea and on a global basis. In summary, some
suggested ways forward are proposed, on the basis of regional scales.
2