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 offered 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 Was flooded, walls in Guildford 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 opportunities
Surface Water
Sustainable solutions for 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
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 Guildford Shalford Meadows Tilford Cranleigh Godalming
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.
Environmental opportunities • Fish passes • Look at additional opportunities for environmental enhancement in the area • Carbon neutral scheme, if possible
River Thames Obstruction to Fish Passage Southern Addlestone Bournes Fish Passes completed/planned Weybridge Chobham Target salmonid spawning grounds Bagshot Wetland creation Woking Hoe Stream North Downs Way Guildford Gomshall Farnham Tillingbourne NorthWey Godalming Leith Hill Cranleigh Cranleigh Alton Waters South Wey Bordon Oakhanger Haslemere 23
St Catherine’s and Unstead fish passes 24
Wetland creation 25
Recent Community Engagement • 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
Guildford Town Centre Regeneration • 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.
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
High Level Economics Scheme Total PV Total Eligible Local LEP Gap High level Costs Maintenance FDGiA Levy Limitations due Costs to high-level 1 in100 SoP £30.5m £2.1m £1.5m £24.1m £4.5m £2.8m stage of - Flood assessment Walls in Guildford and Upstream Storage 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
Updated timescales Activity Timescales 1 in 50 SoP proposal shared with Public November 2018 Winter 2018 Sponsor group request to improve SoP Sponsor group accepts high level June 2019 appraisal for Upstream storage Upstream storage viability assessment November 2019 Upstream storage and Fish passes full March 2020 appraisal Detailed Design & Planning Spring 2022? Construction starts Summer 2022?
Temporary Defence Deployment Plan in Guildford Tina Donaldson 4 November 2019
Background 32
What does a temporary flood barrier look like? 33
Thames Area temporary flood barrier locations We have considered 27 locations 34
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 35
Important to note • 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. 36
Guildford 292m long 22 Required to deploy the temporary barrier: operatives, operatives to site controllers, banksmen, deploy drivers, plus others in the Incident Room 37 Properties Properties better protected 2 Hours to Plus 36-48 hours prepare decision making and site & logistics time. deploy 1 Mary Road Traffic Management Plan
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