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Flood
Policy
Flood
Defence Policies
The Environment Agency's (Agency) flood defence policy
is to protect people and property against flooding,
be it by rivers or the sea. The powers bestowed upon
the Agency to build, improve and maintain defences,
as Operating Bodies is permissive. This means that works
will only be carried out where they are deemed to be
economically, environmentally and hydrodynamically sustainable.
In the Anglian region the Environment Agency's flood
defence team have to contend with a wide variety of
fluvial, estuarine and coastal issues. In the region
varying coastlines exists from the sand dunes of North
Norfolk, to the shingle beaches and spits of Suffolk
and finally the saltmarshes and mudflats of Essex.
Policy Options
In response to these differing coastal environments
there are a variety of policy options available to
the
flood defence teams.
Hold the line
This flood defence policy involves, through intervention, hold
the existing line of defence where it is. This may involve either
maintenance, repair work or improvements to the defence. Due
to sea level rise it may demand substantial modifications or
reconstruction.
Advance the line
Reclamation of the intertidal / subtidal area on the seaward
side of the defence.
No Active Intervention (formerly known as 'Do Nothing')
Ceasing all maintenance, repair and renewal work. No active
intervention may value monitoring of the defences until such
time as a 'Do Something' option is required or the defences
fail.
Limited intervention
This flood defence approach involves not undertaking
any work regarding maintenance and repair to the existing
line of defence unless categorised as emergency works
for health and safety reasons.
Policy Methods
Given the current and predicted rates of sea level rise
for this coast it has become increasingly difficult
to justify building walls higher and higher to keep
the sea out. The Agency is therefore endeavouring to
find more sustainable approaches to flood defence.
Managed realignment, foreshore recharge and regulated
tidal exchange are being put forward as additional coastal
management options in addition to traditional methods
to try and help solve some of the increasing pressures
on our coasts and estuaries.
Managed realignment
Managed realignment involves the partial or complete removal
of a sea wall at a specific site. This allows the tide to inundate
the land during each tidal cycle. Depending on the elevation
of the land in relation to high water the site can then revert
to mud flat or saltmarsh. |
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Managed realignment is not only good for flood defence
purposes but also has potential benefits for wildlife
and local fisheries.
Managed realignment @ Abbotts
Hall Farm, Essex
Foreshore recharge
Foreshore recharge involves the placement of material
in front of existing sea walls and defences.
Recharge works in a similar way as saltmarsh by reducing wave
energy at sea defences. This material would otherwise be dumped
at sea and the sediment would be lost completely from our coastal
systems. This beneficial use of dredgings to protect existing
defences and create new foreshores also saves money. The frequency
of journeys to sea by the dredgers is reduced, as is the amount
of maintenance required at the sea walls.
It is also important to keep coastal sediments within
the coastal system. Foreshore recharge allows sediments
to travel to other parts of estuaries and shorelines
as part of the natural processes that occurs near the
shore. Once sediment has been disposed of at sea it
can only be replaced in the coastal zone by human intervention.
Regulated Tidal Exchange
This process allows the land behind the defence to be
slowly converted to saltmarsh favourable conditions
in preparation for saltmarsh creation. Reversing the
flow through the drainage sluice allows the controlled
flow of seawater to inundate the site. This process
alters the soil chemistry, allows siltation to take
place, permits local species to adjust and encourages
a saltmarsh seed bank to develop.
Sustainable flood defence policies have to look at strategic
planning for our coasts and estuaries and managed realignment
and foreshore recharge are simply two options that can
be considered. There will always be locations that must
be protected by traditional hard defences. Foreshore
recharge and managed realignment can also be seen as
important in terms of creating new habitats, providing
new recreational areas, and producing local economic
gain.
It is hoped that by using options like recharge and
realignment in some estuary and coastal locations, some
of the tidal energy and wave energy can be removed sufficiently
to reduce coastal erosion and flooding elsewhere |
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