Frequently Asked Questions
We have collated a list of commonly asked questions and the respective answers.
What is a 1 in 200 year flood event
It is often believed that a 1 in 200 year flood refers to a flood event that would happen, on average, once every 200 years. In fact, the term refers to the probability of a major flood event occurring in any one year. “1 in 200 years” actually means that, each year, there is a 0.5% chance of a flood of this magnitude happening. This percentage is calculated on the basis of 1 divided by 200 times 100, a recognised formula for the calculation of annual flood risk.
Would dredging reduce the risk of flooding?
Dredging has been considered and shown to offer only very limited benefit to reducing peak water levels in the channel. This activity is not a sustainable solution given the need to frequently re-dredge the watercourses. Where the risk is from the sea, dredging would not reduce the risk of flooding. In addition, altering a river’s natural geomorphological process (sedimentmovement and deposition) can cause erosion of the riverbed and banks, which inturn can lead to the failure of existing structure such as roads and bridges.
Who is funding the scheme?
The FPS process involves submitting an application for funding from the Scottish Government once the Scheme is confirmed. Funding grants of 80 percent of the eligible costs are available from the Scottish Government for confirmed schemes which meet specific technical,environmental and economic criteria. Falkirk Council and others would then fund the remaining 20 percent of the total cost.
Why can't the pumping stations deal with the flooding?
Most of the existing pumping stations in the Grangemouth area are Scottish Water Pumping Stations, which predominantly deal with foul water rather than surface water. The existing pumping stations would not be able to cope with the predicted flows for a 1 in 200-year event.
Does the scheme only protect the refinery
The scheme is not only protecting the refinery. The primary purpose of the scheme is to protect almost 3,000 homes and businesses in Grangemouth and surrounding areas from flooding from the River Carron, River Avon, Grange Burn and the Forth Estuary. The refinery and petrochemical works as well as Grangemouth Port will also be protected given the national importance of the infrastructure to Scotland and the UK economy. In addition, not protecting these areas would leave those resiential properties nearest the Forth Estuary at risk of coastal flooding given the land is low lying.
Will the flood defences be maintained after they are built?
The Flood Risk Management (Scotland) Act 2009 places duties on Falkirk Council to inspect and maintain the defences. They will therefore be kept in good condition and repair and to do so an operational and maintenance procedure will be developed and implemented
When will the scheme be built?
The project team are currently finalising the outline design. This will determine the type of flood defence e.g. wall or embankment and the likely form of construction as well as the height of defence and its location. Thereafter the team aim to publish the scheme in 2021. If all goes to plan and all approvals are granted it is hoped that the main construction works would commence in 2024 with construction potentially being stretched over 10 years.
Will the views of the public be sought on the proposed defences?
To date the project team have held two separate public consultation events seeking feedback on the proposed scheme. In addition there has been consultation with elected councillors, community councils, statutory consultees and many others. This engagement will continue throughout the development and implementation of the scheme
Will the defences stop all future flooding
No, there always remains a risk with every Flood Protection Scheme that
there will be a storm event which delivers a flood bigger than the Scheme is
designed to protect against. The scheme is being designed to protect against flood events that have a 0.5% chance of occuring in any year.
How do flood gates work?
Flood gates are located in specific areas throughout the Scheme, where access through the new flood defences must be maintained. Flood gates are useful where constructing a ramp over the flood defence wall is not feasible and at existing bridges, where the bridge
cannot be raised to accommodate the new flood defence level. Falkirk Council will liaise with SEPA to determine the likely flood level and close the flood gates in preparation for a flood event.
What are flood cells?
The project team have divided the scheme into 6 discreet flood cells which are simply geographic areas. This has been done to make it simpler to refer to these specific areas and present statistics etc. The six cells are: Cell 1 - Upper Carron; Cell 2 - Lower Carron; Cell 3 - Port of Grangemouth; Cell 4 - Grange Burn and Flood Relief Channel; Cell 5 - River Avon; Cell 6 - Estuary Frontage.