Ice midlands region warwick, 2010

11

The Severn Barrage and Other Options: Hydro-environmental

Impact Assessment Studiesby

Roger A. Falconer FREngHalcrow Professor of Water Management

Hydro-environmental Research CentreCardiff School of Engineering, Cardiff University

22

A New Dawn

www.corlanhafren.co.uk

33

General Challenges Growing worldwide increase in energy demand -

particularly in India and China

Tidal energy generation has advantage over wind and waves - in that tides are predictable

UK target of 15% of energy from renewables by 2020 - about 35% of electrical energy

Wales’ 2025 target for marine renewables energy is 14 TWh/yr - Barrage would generate over 60%

Severn Estuary basin is ideal for tidal energy

44

Global CO2 Concentration

Steep increasesince 1800

Roughly constant forhundreds of years

Source - Met Office

55

Predicted Future CO2 LevelsC

O2 c

once

ntra

tion

(ppm

) 750

650

550

450

350

2501990 2010 2030 2050 2070 2090

Year

50% 1990emissions

Constant 1990emissions

Businessas usual

Source: IPCC

66

Predicted Mean Temperature RiseG

loba

l tem

pera

ture

rise

, deg

rees

C High emissionsMedium-high emissionsMedium-low emissionsLow emissions

Source - Met Office

77

Predicted Mean Rainfall Changes

For Wales / SWPresent day wet events with a 5 yr return period are predicted to occur between 1.5 & 8.5 times more often

Source - Met Office

88

Boscastle - Picturesque Village in U.K.

99

Boscastle - August 2004 (1:400 yr flood)

1010

Hurricanes: Link to Climate Change

Source - Jorg Imberger Hurricanes inject large amounts of CO2 into upper atmosphere

By 2034 predicted there will be 50 more category 4 & 5 storms

1111

The Perfect Storm 2030

1212

UK Challenges - Population Growth

Population growthnot just a challengefor developingcountries: UK issue

1313

Planned Renewable Energy Provision

EU target of 20% carbon reduction by 2020

Considerable Scope to increase

1414

Mean Spring Tidal Stream Resource

Source – DTI Atlas ofMarine RenewableEnergy Resources

1515

Mean Spring Tidal Range Resource

Source – DTI Atlas ofMarine RenewableEnergy Resources

1616

WalesWales

EnglandEngland

Severn EstuarySevern Estuary

1717

Proposed Tidal Devices for Severn Tidal Stream Turbines - wind type turbines

located in water column and energy created directly from tidal stream currents

Tidal Lagoons (OTIs) - enclosed embayment constructed offshore, creating tidal phased head difference - similar to barrage concept

Tidal Barrage - embankment across estuary - ideal for renewable energy with high tidal range and large upstream plan-surface area

1818

Potential Power from Tides

2Power A HH = level difference across barrage / lagoonA = wetted surface area upstream of barrage

For tidal barrages and impoundments:-

3Power VV = mean free-stream tidal current

For tidal stream turbines:-

1919

Tidal Stream TurbinesDeltaStream SwanTurbines

Rotor diameter 15m depth 25m to operate

Nominally 1.2MW/unit

2020

Cardiff Turbine Design

Flow

Turbine will operate in any flow depth Design in its infancy – long way to go

2121

Tidal Lagoon Concept

Source – University of Colorado

Swansea Bay Lagoontakes over 8hr to empty

2222

Embankment wall length over 9 km

Plan area 5km2

= 1000 football fields

Mean spring tidal range 8.5 m

Energy output of 124 GWh/yr

Severn Barrage 135 tidal lagoons

Cost £200 m (?)

Key details:

Shape and Scale - Swansea Lagoon

Plan Area

5km2

SwanseaHarbour

SwanseaBay

Source – TidalElectric Ltd

TurbineHousing

2323

Original Proposals

80 km2 ImpoundmentEnvironmental Impact?

2424

EIA Studies Needed for LagoonsModel studies needed to predict changes for:-

Tidal currents:- speed, levels, eddies, river plumes

Wave climate:- height, length, refraction, reflection

Suspended sediments:- distribution along channel

Sediment deposition:- in and out of impoundment

Coastal morphology:- changes to beach profiles

Water quality:- turbidity, nutrients, light penetration

Pre-/post-construction:- short & long term impacts

Mitigating measures:- changes to design/operation

2525

Government Short Listed Proposals

2626

Severn Barrage - 1849

First proposed by Thomas Fulljames - 1849

2727

The Other Challenge

2828

Severn Barrage Proposal SiteSome key facts: 2nd highest spring

tidal range 14 m

Cardiff to Weston

Length about 16 km

Generate 5% of U.K. electricity

Total cost £20 bn

Save > 6.8 million tonnes carbon pa

Slide – courtesyof STPG

2929

Barrage Layout (1989 Report)Key facts:

216 turbines each 40 MW 17 TWh pa

166 sluices

Ship locks

Fish pass?

Public road & railway

Slide – courtesyof STPG

3030

Construction: Prefabricated Caissons

Slide – courtesyof STPG

3131

Turbine Installation

Slide – courtesyof STPG

Slide – courtesyof STPG

3232

Tidal Power Generation

Slide – courtesyof STPG

3333

Proposed Operation - Ebb Generation

Slidecourtesyof STPG

3434

Proven Technology - La Rance

La Rance Barrage, France, has reliably generated tidal power for over 35 years

3535

Barrage Effect on Tides

Estuary Bed

Tide Enters

Severn Estuary

Flow throughturbines

Barrage

3636

Existing Estuarine Environment Tide Range - 14 m on springs, 7 m on neaps

High tidal currents and large inter-tidal areas30 Mt sediment suspended on springs, 4 Mt neapsLittle sunlight penetration through water columnReduced saturation dissolved oxygen levels

EcologyHarsh estuarine regime with high currentsLimited aquatic life in water column / bedBird numbers per km2 are relatively small

3737

Changing Natural Environment Climate Change

Temperature rise will affect ecology, birds etc Sea level rise will lead to increased flood risk

Water Quality Cleaner effluent discharges with EU WFD Nutrient reduction will affect aquatic life

Legislation Long term projects (>120 yr) require assessment

against future - not just current - environment

3838

Wigeon - 8,062Pochard - 880Ringed Plover - 665Curlew - 2,545Whimbrel - 222Spotted Redshank - 10

Wigeon - 3,977Pochard - 1,686Ringed Plover - 227Curlew - 3,096Whimbrel - 246Spotted Redshank - 3

Nationally important bird populations

Shelduck - 3,272Dunlin - 23,312Redshank - 2,566European Goose - 942

Shelduck - 2,892Dunlin - 41,683Redshank - 2,013European Goose - 3002

Internationally important populations of migratory birds

Bewick’s Swan - 276Bewick’s Swan - 289Internationally important populations of Annex 1 species

Species numbers between 2000 – 05(Red - Less, Blue - More)

Species numbers between 1988 - 93Citation category

Source - RSPB

Bird Species in SPA Citation

3939

Main Effects of Barrage Spring tide range reduced from 14 m to 7 m

Significant loss of upstream inter-tidal habitats Reduced currents up & downstream of barrage Reduced turbidity / suspended sediment levels Increased light penetration through water column -

with increased water clarity Increased primary productivity and changed bio-

diversity of benthic fauna and flora

Upstream tidal range of 7m is still relatively large compared to most deltas world-wide

4040

Severn Estuary Hydraulic Model

4141

Severn Barrage - Grid Configuration

Inner Barrage

Cardiff

Frame 001 16 Apr 2008 Initial bathymetry

4242

Grid Refinement Around Barrage

Shipping locks

80 Sluices

12 Sluices

Sub-stations

168 Turbines

48 Turbines

Sub-stations

74 Sluices

Embankment

Flat Holm

Steep Holm

Embankment

Cardiff

Weston

Frame 001 16 Apr 2008 Initial bathymetry

4343

(a) Velocity Field Around Barrage

2 m/swater level(m)

-4 -3 -2 -1 0 1 2 3

Frame 001 12 Apr 2008 Hydrodynamic Results in Nodes

2 m/swater level(m)

2 2.5 3 3.5 4

Frame 001 12 Apr 2008 Hydrodynamic Results in Nodes

Flood

Ebb

4444

Level of water inside impoundment

Option 1: Generate over ebb tide only

Proposed: One Way Generation

4545

Alternative: Two Way Generation

Level of water inside impoundment

Option 2: Generate over full tideRapid filling and

emptying of basin required at either end of tidal cycle

4646

Three Modes of Operation Studied

Wat

er le

vel (

m)

Filling GeneratingHolding Holding

Filling

Hmin

Hst

(a) Ebb Generation

A

BC

D

C

D

Time(h)

Ebb only

Time(h)

Wat

er le

vel (

m)

Generating

Holding Holding

Hmin

Hst

(b) Flood generation

AD

B C

D

Releasing ReleasingFlood only

Time(h)

Wat

er le

vel (

m)

FillingGenerating

Hmin

Hst

(c) Two-way generation

Generating GeneratingReleasing Filling

HoldingHolding

Sea level Basin level

A

B

C

D

Two-way

Model predictions resulted in peak power output for:-Starting Head = 4.0 mMinimum Head = 2.0 m

4747

Maximum Water Levels - Ebb Only

Without BarrageMaximum Water Level (m)

Tenby

Cardiff

Minehead

Weston

Ilfracombe

Barry

Swansea

Gloucester

Newport

BristolAvonmouth

N

4.0

5.5

3.5 4 4.5 5 5.5 6 6.5 7 7.5

Frame 001 05 Nov 2009 Maximum Water Level

With Barrage

Reducedflood risk

4848

Without Barrage

With Barrage

Maximum Water Levels - Two-Way

Reducedflood risk

4949

Peak Water Levels

0

1

2

3

4

5

6

7

8

020406080100120140160180200

Existing

Cardiff-Weston Barrage

Fleming Lagoon

Shoots Barrage

Sw

anse

a

Min

ehea

d

New

port

Avo

nmou

th

Bea

chle

y(M

48)

Sha

rpne

ss

Cardiff

Distance from Gloucester (km)

Hig

h W

ater

Lev

el (m

)(D

atum

rela

tive

to A

vonm

outh

)

Epn

ey

New

nham

5050

Maximum Tidal Currents - Ebb Only

Without BarrageMaximum Velocit y(m/s)

Tenby

Cardiff

Minehead

Weston

Ilfracombe

Barry

Swansea

Gloucester

Newport

BristolAvonmouth

N 0.3 0.7 1 1.3 1.7 2

Frame 001 05 Nov 2009 Maximum Water Level

With Barrage

5151

Maximum Currents - Ebb and Two-Way Maximum Velocit y(m/s)

Tenby

Cardiff

Minehead

Weston

Ilfracombe

Barry

Swansea

Gloucester

Newport

BristolAvonmouth

N 0.3 0.7 1 1.3 1.7 2

Frame 001 05 Nov 2009 Maximum Water Level

Ebb Only

Two-Way

5252

Water levels and Power Output Wa

terLe

vel(m

)

Powe

routp

ut(G

W)

0 2 4 6 8 10 12 14 16 18 20 22 24-10

-9-8-7-6-5-4-3-2-10123456

0

2

4

6

8

10

12

14

16

Time (hour)

Water level (m)Upstream of the barrage

Water level (m)Downstream of the barrage

Power Generation Power Generation24.4 Gwh 24.4 Gwh

I II III II

I=Filling (4.3h)

II=Holding (1.6h+1.0h)

III=Generating (5.5h)

4m

2m

(a) (a)

Water

Leve

l(m)

Powe

routp

ut(G

W)

0 2 4 6 8 10 12 14 16 18 20 22 24-10

-9-8-7-6-5-4-3-2-10123456

0

2

4

6

8

10

12

14

16

Time (hour)

Water level (m)Upstream of the barrage

Water level (m)Downstream of the barrage

PowerGeneration

PowerGeneration

8.3 Gwh 8.3 Gwh15.9 Gwh 15.9 Gwh

I II

Releasing (0.8h+1.1h)

II=Holding (2.0h+1.3h)

III=Generating (2.8h+4.4h)

4m

2m

III III (d)

I=Filling and

(c)

Ebb Only 48.8 GWh/24.8h 5.2 m mean tide High tide 4.6 m

Two-Way 48.4 GWh/24.8h 4.4 m mean tide High tide 3.2 m

5353

High Suspended Sediment Levels

Dynamic region ofhigh turbidity

5454

Suspended Sediment LevelsMean Flood

Without Barrage With Barrage

Mean Flood - Spring Tide

Reduced sedimentlevels & clearer water

5555

Effects of Turbidity Changes

But what type of birds?Dunlin or other birds?

5656

Riverine and WwTW Source Inputs?

RiversRivers

WwTWsWwTWs

5757

EU Bathing Water Directive

5858

Diffuse Pollution Effects?

Wales Population: Humans - 2.75m Sheep - 10.5m

5959

Enteric bacteria

water columnWastewater outfallsCatchment runoffWater birds

input

Advection with diffusion/dispersion

outputOverall reduction

DecayAdsorptionDeposition

Sediment re-suspensionand desorbed into water

Enteric Bacteria Flux

6060

Enterococci T90 Experiments Samples taken from 5

sites along estuary

Dark and irradiated microcosms tested4 times for each site

Cellulose diacetate bandpass filter

Mixing unit

Chiller/heater Matt black lining

Artificial light source calibrated to provide average radiation conditions during July and August

6161

Relationship with Turbidity/SS Empirical relationships developed between turbidity and

suspended solids and T90 values Real-time T90 included in numerical model - varying with

time, location, predicted SS level and radiation patterns

6262

Sediment Associated Experiments 2 Two beakers incubated at 15˚C one mixed and one

allowed to settle - two sites tested

Mixed beaker -concentrations remained constant

Settled beaker –concentrations fell as finer particles settled

6363

Mean Ebb

Bacteria Levels

Without Barrage With Barrage

Mean Ebb - Rivers in Flood

Reduction inbacteria levels

6464

Welsh Grounds Lagoon

6565

2 2.5 3 3.5 4 4.5 5 5.5 6

2 m/s

Water level (m)

Flood

Frame 001 01 Sep 2008 Hydrodynamic Results in Nodes

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

2 m/s

Water level (m)

Ebb

Frame 001 01 Sep 2008 Hydrodynamic Results in Nodes

Velocity Field Around Lagoon

(a) During Filling Mode (b) During Generating Mode

6666

Water

Level

(m)

Powe

routp

ut(M

W)

0 2 4 6 8 10 12 14 16 18 20 22 24-10

-9-8-7-6-5-4-3-2-10123456

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Time (hour)

Water level (m)Upstream of the lagoon

Water level (m)Downstream of the lagoon

Power Generation Power Generation

I – FillingII – HoldingIII – Generating

I II III

Predicted Power Generation

6767

Shoots Barrage

Shoots Barrage

Second SevernCrossing M4

Severn Bridge

Key facts

30 x 7.6m diam 35 MW turbines 2.75 TWh/yr

Construction period ~ 4 yr

Less plan area

Slightly higher tidal ranges

Cost £2.6 bn

6868

Other Issues to Consider Barrage would bring jobs:

30,000+ jobs at construction peak, distributed over UK - about half in Cardiff - Bristol region

10,000+ permanent jobs in Severnside

Regional economic impact: Availability of skilled labour and materials? Local infrastructure needs - housing, schools etc Concerns about supply chain, deep ports etc Opportunities for expansion of Port Talbot etc Considerable tourism and recreational potential Road / rail links between Wales, London and EU

6969

Summarising Severn Barrage would have a lasting impact on a

unique UK macro-tidal estuary: Provide 5% of UK’s electricity from renewables Reduce intertidal habitats by about 14,000 ha Reduce flood peaks - upstream and downstream Reduce tidal currents and suspended sediments -

increasing light penetration and water clarity Change ecology and benthic flora and fauna Enhance opportunities for tourism and recreation Two-way generation - enables optimal energy

provision for minimal environmental change Fish migration would remain a major challenge

7070

UK Relative Water Stress

High water stress

Low water stress

7171

Severn Barrage: More than a Renewable Energy Project

7272

BBC Documentary on Barrage by

Jonathan Porritt

7373

7474

Addendum

7575

The ChallengeThe Challenge For engineers and scientists to deliver For engineers and scientists to deliver UK’s marine renewable energy targetsUK’s marine renewable energy targets

The OpportunityThe OpportunityFor UK to deliver renewable energy For UK to deliver renewable energy with minimal environmental impactwith minimal environmental impact

7676

Thank YouThank You

Professor Roger A. FalconerEmail: FalconerRA@cf.ac.uk