Lancaster University
Renewable Energy Group
An assessment of the environmental
impacts of a tidal barrage scheme at
Fleetwood
Students:
Christopher Betteridge, Lawrence Chamboko, Wang Xiaofei
Supervisor: Dr George A Aggidis
3/2/2011
Lancaster University
Renewable Energy Group
• Introduction
• Aims and Objectives
• Methodology
• Conclusions
• Next steps
Overview
Lancaster University
Renewable Energy Group
Introduction
• Located in Lancashire, catchment of 548 km2
• River is 800m wide, with a 200m channel, and 600m of
mudflats and sandbars
• Salt marshes to the west, regularly flooded
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Lancaster University
Renewable Energy Group
Aim
• To assess the environmental impacts of a tidal
barrage on the Wyre Estuary.
• To assess the feasibility of implementing a
barrage, with regards to the environment.
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Lancaster University
Renewable Energy Group
Effects on Water Level
Fig.1 Typical tidal curves in open and impounded
estuary with a barrage
P. M. Parker
Lancaster University
Renewable Energy Group
Effects on Water Level
• Seaward:
a) The rise of low water level adjacent
to the barrage
• Landward:
a) The rise of the low-water level
b) The prolonging of the high-water
stand
Effects on Water Quality
Lancaster University
Renewable Energy Group
Water qulity
parameter
Changes caused by
barrage
Reason
Salinty
a maximum increase
of 5ppt
Prolonged retention of
saline water
Dissovled Oxygen
a maximum decrease
of 0.5mg/L
Redouced water
flushing
Biochemical Oxygen
Demand (BOD)
a maximum decrease
of 0.9mg/L
Increased dilution at
low water
Ammonia
a maximum decrease
of 0.3mg/L
Increased dilution at
low water
decrease in Knott End
Increased dilution
increase in Cartford
Accumulation over the
prolonged retention
Phosphorus
Table ? water quality impact by wyre barrage
Other Implications
Lancaster University
Renewable Energy Group
• Land Drainage
• Bank
• Shoreline
• Sediment Movement
Emission Reduction
Lancaster University
Renewable Energy Group
Pollutant
Coal equivalent
(tonnes, Per annum)
Carbon dioxide
153,000,000
Sulphur dioxide
1539
Nitrogen oxides
442.4
Carbon monoxide
250
Particulates
115.4
Heavy metals
0.026
Table ? : Atmospheric emissions from coal-fired generation which would be avoided
Lancaster University
Renewable Energy Group
•
Environmental impacts
of tidal barrages on
plants
Barrages reduce tidal height
• They can affect the extent of salt marshes
which support an array of diverse flora
• The salt marshes of the Wyre Estuary for
example support some endemic species such
as the rock sea lavender, the sea aster and
the sea purslane which are priority species.
Lancaster University
Renewable Energy Group
The effect of a tidal
barrage on nutrients
• Impounding water behind a barrage also leads to nutrient
build up with an increase in nutirients such as nitrogen
and phosphorus.
• Nutrient build up in turn could lead to a bloom in algae
and phytoplankton
• These algal blooms could have both negative and
positive ecological impacts
Negative impacts
Lancaster University
Renewable Energy Group
• These blooms could lead to a decrease in the biological
oxygen demand (b.o.d) of the estuarine waters
• This is due to the high demand for oxygen by the
decomposer community, which ultimately feed on the
dead phytoplankton from these algal blooms
Positive Impacts
Lancaster University
Renewable Energy Group
• Any bloom in the estuarine phytoplankton and algae
community could lead to an increase in filter feeding
invertebrate populations and ultimately to an increase in
the density of feeding birds which feed on these
invertebrates.
• Increases estuarine ecological productivity
Lancaster University
Renewable Energy Group
Environmental impacts
of barrages on
invertebrates
• Because barrages lead to increases in bod, this affects
water quality and ultimately estuarine invertebrate
populations.
• With reference to the Wyre estuarine ecosystem,
populations of brown shrimp, edible cockles and mussels
could be adversely affected.
Lancaster University
Renewable Energy Group
Overview of the types
of vertebrates found in
and around the Wyre
Estuary
• Fish and shellfish
• Birds
• Marine mammals
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Conservation sites
Lancaster University
Renewable Energy Group
16
Impact on vertebrates
Lancaster University
Renewable Energy Group
• Fish and shellfish- Risk of injury by collision with turbine
blades, and injury through related hydraulic effects.
• Changes to water quality- dissolved oxygen, turbidity,
contaminants, salinity.
• Changes to prey resource, habitats, and migration
patterns. Noise disruption.
• Birds- Reduction in intertidal area and a reduction in
feeding time.
• Changes in nesting and roosting areas
• Possible increase in prey and ease of feeding
• Mammals- Few effects, possible deterrence from 17
estuary
Mitigation measures
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Renewable Energy Group
• Fish injury- Mesh screens, fish
passes, acoustic systems, low
speed turbines
• Birds- Artificial reefs and
roosting sites, creation of an
alternative habitat to offset lost
habitat
• Mammals- Use of similar
schemes as those used for fish
(screens, acoustic devices).
Nets and barriers could direct
animals to passes or pens,
where they can be transported
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across the barrage.
Lancaster University
Renewable Energy Group
Impacts of tidal stream,
tidal lagoon, and tidal
fence
devices
on
vertebrates
• Fish-Similar, but lesser effects than tidal barrage. Fish
can swim around device! Tidal stream devices have the
lowest environmental impact.
• Birds- Lagoons would have similar effects to a barrage,
however submerged tidal stream and fence devices are
likely to have negligible effects.
• Mammals- Effects almost identical to that of fish
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Mitigation measures
Lancaster University
Renewable Energy Group
• Fish- Mesh screens, behavioural barrier devices, e.g.
lights and sound, have achieved 60- 100% diversion
rates in tests. Low speed turbines cheapest and easiest
option if sufficient power can be drawn.
• Birds- Alternative habitat would need to be created
under the habitats directive. E.g. alternative feeding or
roosting areas. Regulation of recreational use of estuary.
• Mammals- see fish.
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Conclusions
Lancaster University
Renewable Energy Group
• A tidal barrage is feasible in terms of environmental
effects, so long as adequate measures are taken to
mitigate potential adverse effects. The cheapest and
easiest method to prevent fish and mammal injury is low
speed turbines, however acoustic devices have also
been shown to be effective.
• With regards to birds, any habitat changed or lost needs
to be recompensed.
• Tidal barrages can have numerous positive effects on
the environment.
• Other methods of tidal energy generation have less
effects on the environment overall, compared to a tidal
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barrage.
Lancaster University
Renewable Energy Group
An assessment of the
environmental impacts of a
tidal barrage scheme at
Fleetwood
Thank You
Students:
Christopher Betteridge, Lawrence Chamboko, Wang Xiaofei
Supervisor: Dr George A Aggidis