Lancaster University Renewable Energy Group

Students: Christopher Betteridge, Lawrence Chamboko, Wang Xiaofei

Supervisor: Dr George A Aggidis

3/2/2011

An assessment of the environmental impacts of a tidal barrage scheme at

Fleetwood

Lancaster University Renewable Energy Group

Overview

• Introduction

• Aims and Objectives

• Methodology

• Conclusions

• Next steps

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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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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Effects on Water Level

Fig.1 Typical tidal curves in open and impounded estuary with a barrageP. 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

Lancaster University Renewable Energy Group

Effects on Water Quality

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 decreaseof 0.9mg/L

Increased dilution at low water

Ammoniaa maximum decrease

of 0.3mg/LIncreased dilution at lo

w water

Phosphorusdecrease in Knott End Increased dilution

increase in Cartford Accumulation over the prolonged retention

Table ? water quality impact by wyre barrage

Lancaster University Renewable Energy Group

Other Implications

• Land Drainage

• Bank

• Shoreline

• Sediment Movement

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Emission Reduction

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

Lancaster University Renewable Energy Group

Negative impacts

• 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

Lancaster University Renewable Energy Group

Positive Impacts

• 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

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Impact on vertebrates

• 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 estuary17

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Mitigation measures

• 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 across the barrage.

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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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Lancaster University Renewable Energy Group

Mitigation measures

• 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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Lancaster University Renewable Energy Group

Conclusions

• 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 barrage.

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Lancaster University Renewable Energy Group

Students: Christopher Betteridge, Lawrence Chamboko, Wang Xiaofei

Supervisor: Dr George A Aggidis

An assessment of the environmental impacts of a tidal

barrage scheme at Fleetwood

Thank You