Guildford Flood Alleviation Scheme Community Forum 4 November 2019 - - PowerPoint PPT Presentation

Guildford Flood Alleviation Scheme Community Forum

4 November 2019 Justine Glynn Ivan Parr Tina Donaldson

Agenda

• Introductions
• Meeting aims
• Guildford flooding - background
• Guildford FAS
• Temporary Flood Barriers
• Any Other Business

Aim for Today’s Meeting

• Inform and update community and organisation

representatives about the Guildford Flood Alleviation Scheme and answer any questions.

• Inform the community forum about local temporary flood

barriers for Mary Road area, Guildford.

• Establish format and frequency for future meetings.

Guildford Flood Alleviation Scheme Aims

Study Area

Guildford 2013 flooding

Guildford - Historic Flooding

Guildford Modelled Flood Map

Guildford Scheme history

Many schemes proposed along the River Wey since the 1968 flood

• 2002 Pre-Feasibility Study – Outline review identified viable options recommending a

detailed feasibility study

• 2010 River Wey Flood Risk Management Study – looking at catchment wide options
• none of these could reduce flood risk to all the communities on the Wey. Strategy identified

local defences in Guildford but not progressed as the options were not technically or economically viable

• 2013/14 - flooding led to review the work already carried out. A mix of different options

(Permanent Flood Walls, Temporary Demountable Defences and Property Level Protection).

• Guildford Flood Alleviation Scheme starts

Current scheme evolution

• 1:50 Standard of Protection (SoP) most economically viable scheme - Wall height

0.3m to 1.5m

• 1:100 SoP walls too high and location unacceptable to many landowners but
• ffered greater protection for residents, businesses and infrastructure
• GBC see the FAS project as a catalyst for change and an opportunity for town

centre regeneration.

• Working with GBC on their Town Centre Development Planning Document to help

fund the scheme.

• Hybrid solution providing upstream storage and 1:50 SoP walls to give 1:100 +

climate change SoP.

• Wall alignment is not fixed

Guildford present day flood risk

Upstream Storage + Walls = Benefit to Guildford

Upstream storage + 1 in 50yr high walls in Guildford Was flooded, now protected Was flooded, now protected Pre Scheme Flooding Post Scheme Flooding

Guildford Proposed Flood Defence Alignment

Walnut Tree Close – indicative set back alignment

Bedford Wharf possible flood wall alignment

What would the defence look like?

Facilitating Growth and Regeneration

Waterfront access and green corridors

Facilitating Growth and Regeneration

Public realm improvement

• pportunities

Surface Water

• Aim to keep roads and railway open during a flood
• Surface water flooding a problem in Guildford
• Flap valves for discharge into the river
• Surface water disposal hierarchy – avoid pumping!
• Small scale upstream storage - slowing the flow

Sustainable solutions for surface water

Guildford - Upstream Storage

Targets

• To increase Standard of Protection at Guildford using upstream

storage

• Investigate benefits to communities downstream of storage
• Reduce flood flows in Guildford
• Feasible water levels and volumes stored upstream - dams and

natural flood management

• Minimal impact on designated sites, critical infrastructure and

existing property.

Guildford - Upstream Storage

Why?

• Reduce flooding in Guildford by storing water upstream.
• Increase Standard of Protection of current preferred flood defence without

increasing its dimensions.

• Other areas could benefit from flood depths reductions.

Key limitations with upstream storage:

• Land availability (location, extensive area)
• Technical feasibility (large volumes, Reservoir Act)
• Cost
• Impact on designated sites and the wider environment

Possible Upstream Storage Locations

Flood defence (walls + temporary barriers) + upstream storage

Cranleigh Tilford Godalming Guildford Shalford Meadows

What could the storage look like?

Dam across the floodplain to retain water upstream. A control structure within the channel would limit the flows released downstream. A fish pass at the structure or bypassing it would allow fish migration.

• Fish passes
• Look at additional opportunities for environmental

enhancement in the area

• Carbon neutral scheme, if possible

Environmental opportunities

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Guildford Godalming Bordon Farnham Alton Haslemere

Cranleigh

Gomshall North Downs Way Leith Hill Woking Weybridge Addlestone Chobham Bagshot River Thames Southern Bournes Hoe Stream Tillingbourne NorthWey South Wey Oakhanger Cranleigh Waters

Obstruction to Fish Passage Fish Passes completed/planned Target salmonid spawning grounds Wetland creation

St Catherine’s and Unstead fish passes

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Wetland creation

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• Drop-ins Nov 2018
• 4 Nov 2019 community forum
• Newsletter and drop-in early 2020
• Future engagement?
• What?
• Who?
• How?
• When?
• Where?
• Upstream storage Engagement

Recent Community Engagement

• Working with GBC planners, Surrey County Council,

Enterprise M3 LEP – other organisations welcome

• Steering Group start up meeting 30 August
• EA/GBC coordinated approach to developer engagement
• Developers’ Forum for those landowners/developers

benefitting.

Guildford Town Centre Regeneration

Funding

Partnership Funded Scheme

• Allocation of Grant in Aid
• RFCC Local Levy
• LEP Local Growth Fund Bid
• Partner Contributions
• Landowners benefitting to contribute
• Upstream storage flow reduction benefits

Scheme Total PV Costs Total Maintenance Costs Eligible FDGiA Local Levy LEP Gap 1 in100 SoP

• Flood

Walls in Guildford and Upstream Storage

£30.5m £4.5m £2.8m £2.1m £1.5m £24.1m

High Level Economics

High level Limitations due to high-level stage of assessment

Present value measures the worth of a future amount of money or stream of payments in today’s pound adjusted for interest and inflation. Gap: £24.1m  additional contributions required

Activity Timescales

1 in 50 SoP proposal shared with Public November 2018 Sponsor group request to improve SoP

Winter 2018

Sponsor group accepts high level appraisal for Upstream storage June 2019 Upstream storage viability assessment November 2019 Upstream storage and Fish passes full appraisal March 2020 Detailed Design & Planning Spring 2022? Construction starts Summer 2022?

Updated timescales

Temporary Defence Deployment Plan in Guildford

Tina Donaldson 4 November 2019

Background

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What does a temporary flood barrier look like?

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Thames Area temporary flood barrier locations

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We have considered 27 locations

We have used a range of criteria to decide where temporary defences could be used

The barrier will protect more than five properties, from a 3.3% (1:30) chance of flooding in any year Offer a practical method of reducing the impact of flooding and are economically viable Will not significantly increase the impact of flooding elsewhere for other properties or communities Would not encircle and therefore isolate the community from additional support Our ability to forecast flooding gives us enough time to deploy the defences There is support from the local authority, partner organisations and the community

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Important to note

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• These alignments are subject to change due to ongoing

investigations into these locations, as well as discussions with residents and landowners.

• Temporary barriers do not offer the same standard of

protection as a permanent defence. There is no guarantee they will be deployed every time because each flood is different and temporary defences do not work in all situations.

292m

long

Required to deploy the temporary barrier: operatives, site controllers, banksmen, drivers, plus others in the Incident Room Properties better protected

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• peratives to

deploy

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Properties

Guildford

Mary Road

Plus 36-48 hours

decision making and logistics time.

2

Hours to prepare site & deploy

1

Traffic Management Plan