crisis in shrewsbury

Crisis in ShrewsburyCrisis in Shrewsbury

Flooding impacts and risk Flooding impacts and risk managementmanagement

Responsibility and Responsibility and managementmanagement

Under the ‘Water resources act 1991’ the Environment Agency have a duty to...

‘…protect people and resources threatened by river and sea flooding’.

Dealing with high riskDealing with high risk

Pre-disaster planning Preparation Response Recovery and

reconstruction

Flood alleviation in Flood alleviation in ShrewsburyShrewsbury

Flood alleviation strategies have been proposed from 1956 to the present day

1:100 floods cost an estimated £4m The NRA (now Environment Agency)

commissioned the latest study in 1993. 3 options

• Upstream storage• Channel enlargement by dredging• Hard defences (cost effective option -

£3.1m)

Floodwater Containment UpstreamFloodwater Containment Upstream

The River Vyrnwy doubles the River Severn discharge during flood risk periods.

Water encouraged on farmland upstream of Shrewsbury at confluence

Discharge slowed

BUT – rejected on a cost benefit analysis -

Compensation to landowners for loss of land = £18 million.

Channel Enlargement by DredgingChannel Enlargement by DredgingThis would:

• Deepen the river

• Increase the efficiency

Allow the channel to contain more water within its banks during periods of peak flow.

However, the channel would need to be 35 meters deep!

This would be prone to re-silting which would incur even more costs.

Hard defences and drainage Hard defences and drainage modification within the townmodification within the town

Defence walls at key locations in the town to hold back flood water.

One way valves included to stop water backing up and flooding out of the drains.

Cost would be £3.1 million.

This was the only option considered cost effective by the EA.

Planning application was made in 1993 Proposed scheme…

• Include walls, floodgates and ‘one-way’ drain valves in a two phase development…

Phase 1 - Based in Frankwell Phase 2 - Based on English Bridge

Proposal rejected - May 1996• ‘unacceptable impact on the town’s river side

character’ NRA (1996)

Hard defences...Hard defences...

In Oct. 1998 Shrewsbury experienced its largest flood for 30 years (1:60 yr. event)

And in Nov. 2000 Shrewsbury again was devastated by its largest flood for 50 years

(1:50-70 yr. event)

EA have acknowledged a significant increase in the frequency of floods events since 1998

(EA 2001)

And what happened...And what happened...

B4393 Crew Green to Llandrinio Road

Frankwell, Shrewsbury.

Frankwell Car Park, Shrewsbury.

English Bridge, Shrewsbury.

Gay Meadow Football Ground, Shrewsbury.

Linked to the River Severn Strategy (EA)...

...the EA have proposed the latest flood alleviation strategy for Shrewsbury.

Based on…• the work in 1993 • the latest flood protection systems • and full communication with interested parties

Renewed calls for action...Renewed calls for action...

What is happening?What is happening?

The EA split Shrewsbury into “Cells” – each for consideration and Cost Benefit Analysis -

Work is funded by local authorities and grants from Central Government.

FrankwellFrankwell

River Severn

Car park

Housing

Shrewsbury and Atcham Borough Council granted planning permission for Phase 1 on 4th July 2001...

Formal application made to DEFRA (Department for the Environment, Food and Rural Affairs) for funding...

Accepted - construction work started early 2003

Completed Autumn 2003

So what’s the latest?So what’s the latest?

Frankwell – hard defencesFrankwell – hard defencesThe scheme incorporated demountable barriers which are only deployed prior to flooding.

Temporary Flood DefencesTemporary Flood Defences

Two other temporary flood defences will be trialled in Shrewsbury

Mobile Dam – which consists of two tubes fitted together and filled with water to create a dam.

Temporary Flood DefencesTemporary Flood Defences

Pallet Barrier – which is a metal frame on which wooden pallets and plastic sheeting are placed to retain the water

Defences testedDefences tested

Defences were tested Defences were tested during the flooding in during the flooding in Feb 2004Feb 2004

Defences testedDefences tested

Other areas not so protectedOther areas not so protected

Other areas not so protectedOther areas not so protected

Other areas not so protectedOther areas not so protected

They await the success of Phase 1 Phase 2 - English Bridge area - does not

currently meet cost benefit requirements.

R. Severn Management Strategy Continued monitoring...

• R. Severn• Climate• Catchment response

Pre-planning (e.g Flood Warnings) Increase awareness (e.g. Floodline)

Continuing work by the EA...Continuing work by the EA...

Summary of the proposed schemesSummary of the proposed schemes

SchemeScheme CostCost EffectivenessEffectiveness Environmental Environmental ImpactImpact

ContainmentContainmentToo high at over £18 millionToo high at over £18 million Would protect area downstream, including Shrewsbury Would protect area downstream, including Shrewsbury Loss of agricultural land, but creation of new wetlandLoss of agricultural land, but creation of new wetland

DredgingDredgingToo high would require repeat dredgingToo high would require repeat dredging Would only work in channel re-dredgedWould only work in channel re-dredged Destroys aquatic habitats and river would have high Destroys aquatic habitats and river would have high

muddy banks during low dischargemuddy banks during low discharge

Hard Hard DefencesDefences

£3.1 million£3.1 million Would protect Shrewsbury with minimal impact Would protect Shrewsbury with minimal impact elsewhereelsewhere

Minimal impactMinimal impact

Flood defence optionsFlood defence optionsOptionOption Positive Positive NegativeNegative Cost Cost

(£million)(£million)

Do NothingDo Nothing 00

Maintenance onlyMaintenance only 0.10.1

Upstream Upstream Containment/storageContainment/storage

24.324.3

Hard DefencesHard Defences 66

Storage and hard defencesStorage and hard defences 7.97.9

Dredging and re-routing Dredging and re-routing river channelriver channel

30+30+

Why locate in high risk Why locate in high risk areas?areas?

Risk perception• Understanding based on experience• Low frequency of high magnitude events

may induce complacency

Knowledge Benefits outweigh potential costs Necessity

EIA for Phase 1 completed Jan 2001.• Work based in Frankwell, Shrewsbury• Objective analysis of impacts by new developments• Statutory obligation for major projects

Stages…• Problem Identified - national and local relevance • Scoping Report - sets out problems• Consultation, feedback and option evaluation• Planning application with env. action plan

EIAEIA((Environmental Impact Assessment)Environmental Impact Assessment)

Rejected for aesthetic Rejected for aesthetic reasons? or was it reasons? or was it something else…?something else…?

Decades of the C20th Metres above Gauge Datum. 20’s 30’s 40’s 50’s 60’s 70’s 80’s 90’s

Total

3.0-3.25 4 2 3 6 6 21 3.26-3.5 1 4 4 5 7 6 27 3.51-3.75 1 2 1 1 4 1 6 3 19 3.76-4.0 2 2 1 1 6 4.01-4.25 2 1 3 6 4.26-4.5 2 1 2 5 4.51-4.75 2 2 4 4.76-5.0 1 2 2 5 5.01-5.25 1 1 2 5.26-5.5 2 2 4 5.51-5.75 1 1

Total No. Of Floods 7 5 10 13 15 9 20 21