Geography Reference
In-Depth Information
An alternative strategy to sea walls is to reduce the incoming
wave energy by installing submerged breakwaters parallel to the
shore that encourage waves to break further away from the land.
These features must be porous so that they allow sediment to
move through them and are usually built as a series to protect a
stretch of coast. They are very expensive to install because they
must withstand extreme wave action and are placed within the
most energetic part of the nearshore zone. Building beaches is
another solution to coastal erosion. This involves artificial deposi-
tion of sediment on the beach or in the nearshore zone in order to
advance the shoreline seaward. However, this sort of approach can
often treat the symptoms and not the causes of the erosion
problem and beach nourishment can simply be followed by net
erosion. Officials in Miami Beach, Florida spend millions of dollars
every few years transporting sand to replenish the beach. Gener-
ally the sand used for beach nourishment must be coarser than
local sediment in order to minimise rapid sediment loss offshore.
Groynes are often installed in beaches to trap sediment moving via
longshore drift. The groynes can be buried by sediment allowing
longshore drift to recommence. A problem with groynes is that
rip currents sometimes develop on their downdrift side which
consequently moves sediment offshore and away from the beach
system. Therefore some groynes constructed with bends to coun-
teract this effect. Jetties are built to line the banks of tidal inlets or
river outlets to stabilise the waterway for navigation. However,
these jetties often encourage deposition on the updrift side and
erosion downdrift. This occurred in the 1920s at Santa Barbara,
USA, where the harbour infilled with sediment. Further down the
coast, as a result, the whole community became at risk from
coastal erosion.
Overall there are probably four main strategies for dealing with
coastal erosion and sea level rise. These are: doing nothing, aban-
donment, adaptation or protection. The first option might be most
costly as it leaves infrastructure and people at risk and so can only
be realistic if the area is sparsely populated. Abandonment is where
people and industry leave the coastal setting and move inland and
also where further coastal development is prevented. Adaptation
involves designing features into the landscape to cope with change
such as building homes on stilts or providing warning systems.
