Property flood protection – two good reasons for early planning9 August 2022
There are important long and short-term reasons for taking early steps to protect exposed properties from rising sea levels, river flooding, saturated ground, damaged culverts, and other local surface and sub-surface flood vulnerability problems.
Location and circumstances are clearly crucial in any flood risk assessment, as are personal and corporate attitudes to probability and risk, plus costs and savings.
However, while there are many ways of coping with flood events, the case study shown in a moment helps to illustrate how typical practical factors found on many sites can be combined efficiently.
Long-range weather forecast
Why is this so important just now?
The unfortunate fact is that, even given huge variations in seasonal weather from year to year, more homes, civic and business premises are facing damaging risks from increasingly erratic and intense flooding as the frequency, intensity, and unpredictability of storms increases.
And this is expected to rise exponentially in the future.
Living with change
The short and long-term driver is, of course, global warming and associated climate change that make it ever more important to prevent, minimise, or learn-to-live with sudden flood events.
And while we are increasingly having to take extra steps to protect against the risks of a 1-in-20 year event, it is important to remember that a more damaging a 1-in-100 year extreme mega-storm could strike hard tomorrow – and several times again in the next 99 years. Statistics!
The recommendation, therefore, is to understand your risks now, make key decisions, and prepare accordingly.
However, there are many practical precautions we can take before the waters begin to rise.
The worst may never happen, but if it does …
Barriers to keep high water levels at bay, site-specific business continuity plans, evacuation procedures, plus post-event recovery strategies will, hopefully, be never, or seldom, used in anger.
But if they are, having appropriate insurance cover in place is reassuring and essential. Proof of effective and cost-efficient flood protection planning may also be needed for business finance applications.
Professional flood risk assessments and well-designed protection measures as part of a property flood resilience (PFR) inspection carried out by Enzygo expert team of environmental consultants (www.enzygo.com) can save early pounds and pence (https://www.enzygo.com/hydrology/).
And if the worst does come to the worst, having assurance that products, materials and service used in flood protection are suitable for the conditions and meet requisite standards and regulations is a further bonus.
Calculations before the event
In the present febrile environment, the threefold strategy is: – installing defences to resist and minimise flooding (mitigation), developing the ability to bounce back quickly when levels fall again (resilience), and learning to live with water when it becomes an inevitable way of life (adaptation).
Getting the balance right depends on individual estimates of cost, lost revenue opportunities, damage and duration.
However, at a local level making good flood protection decisions is more complicated still, and this is where basic guidance and case-history pointers can be useful.
In a moment, as environmental planning consultants with extensive experience in conducting flood risk assessments we will look at an example built around an actual case to demonstrate a practical approach to factors that may need to be included in typical property flood protection proposals.
We’ll also look at a model of measures that can be taken for properties in the worst circumstances.
Risks and cost options
That brings us to costs, plus cost-based decisions such as options for passageways and entrances that may not be used regularly.
This can dictate the type of protection installed if – again as an example – a doorway is only used occasionally, particularly if it is out of sight and out of mind (See ‘doors with no barriers’ note below.)
Even then, decisions are not necessarily straightforward. Where corridors are used frequently, say during the ordinary day or night, active decisions may have to be taken to put them into safe mode by qualified staff if flood waters are expected to rise.
Entrances used less frequently at, say, the rear of buildings, can be flood doors that are locked when Flood Alerts or higher are in force, leaving only regular used entrances as removal flood barriers to be closed at the last moment.
Going further still, removable barriers are often an alternative to doors. However, to be used they may need to be taken out of safe storage and installed correctly at short-notice.
That brings into the question training and whether staff are supervised competently, maintenance and repair issues, plus the option of passive measures (flood-proof doors) that continue to do their job while kept closed and are particularly useful for infrequently used openings.
The result is a more complicated equation that has to be considered carefully in individual flood risk assessment and protection plans.
When push comes to flood
In more extreme cases, for example where properties are at risk to rising sea levels, say, along the UK’s east and southeast coast, flood-prone rivers like the Severn, or exposed estuaries such as the Humber or flood plains, a whole list of special measures may be needed.
A wealth of background advice is available here, such as ‘Six Steps to Flood Protection’ from the National Flood Forum (https://nationalfloodforum.org.uk/about-flooding/reducing-your-risk/protecting-your-property/), or ‘Protecting property from flooding’ from the Met Office (https://www.metoffice.gov.uk/weather/warnings-and-advice/seasonal-advice/your-home/protecting-your-property-from-flooding).
If you want to know more about post code-specific flooding risks, you can also find your vulnerability at https://www.gov.uk/check-long-term-flood-risk. The service shows: – the long-term flood risk for any area in England; possible causes of flooding; and advice on flood risk management.
It also explains what the long term risk is from: – rivers and the sea; surface water; reservoirs; and some ground water sources.
Leaving no stone unturned
A complete list of precautions for properties in very vulnerable cases could include: –
Fitting non-return valves to sewer pipes, using sumps and pumps to remove water, installing tiled floors with waterproof adhesive and grout, making the bottom steps of ground floor staircases of concrete with removable carpets, and installing waterproof ground floor outer doors.
Other measures might be to raise electrical sockets well above ground floor level, use resilient plaster or plasterboard, stand vulnerable white goods like fridges on plinths and kitchen units on legs concealed by removable kickboards, install closed-cell insulation, relocate boilers on upper floors, fit air brick covers, and seal appliance and cable entry points.
Further options are to fit flood resistant windows, have separate electrical circuits for upper and lower floors, lay permeable surfaces on drives and paths, consider using easily stored and accessible flood gates and barriers, seal brickwork … and keep important documents upstairs!
Meanwhile, the following example may be relevant to many medium-sized office or business premises, hotels, health centres or administration centres where reasonable steps are needed.
In this case, the assumption has been made that flood water levels will not rise above a 0.6m site datum level. Any anticipated rise above this would automatically involve a structural survey.
Rather than going into more detail about that here, we are happy to answer specific questions or discuss individual site issues if you would like to contact us directly at https://enzygo.com/.
Case study details
The case we will consider is a property flood resilience (PFR) inspection and report that might typically be for a hotel or similar building. The aim is to understand what PFR currently exists and can be deployed, plus to recommend additional measures that will help the client secure funding and insurance cover.
– Methodology – typically, we first visit a site to collect property imagery and review flood resilience products, plus how they are installed to prevent flood risk. Next, we recommend and compare potential product options. Finally, we provide approximate costs.
Logically, we then set out; 1) a summary of baseline flood risk, property vulnerabilities and countermeasures with recommendations for resistance and resilience; 2) approximate costs based on Defra price estimates; 3) a comparison of optional products; and 4) a summary and conclusions.
– Vulnerabilities and countermeasures – we use the imagery and drawings to show threshold heights of vulnerabilities in metres above surrounding ground levels. These are also referred to meters Above Ordnance Datum (mAOD).
Vulnerabilities are only shown at 0.60m, or less, above ground level because, as explained, above this a structural survey is required; 0.60m is also the industry standard for testing resilience products to the BS 845118 standard.
We then list vulnerabilities and corresponding countermeasures. In the model we consider here, they might typically include: –
– Doors with leaking flood barriers – that can be replaced with new barriers, gates or flood doors.
– Doors with no barriers – where flood barriers, gates or flood doors could now be fitted (see note above)
– Windows – that can be protected with demountable window guards.
– Electric/cable boxes – that can be protected with a silicon sealant.
– Airbricks and vents – that can be replaced by auto-bricks which allow ventilation.
– Pipe holes in the ground – where bespoke sealing systems are needed.
– Old silicon holes – where the silicon can be removed and replaced with water-resistant mortar.
– Boiler overflows and taps – where again a silicon sealant can be used.
– Large cracks – that can be sealed with water-resistant mortar.
– Foul manholes – where non-return valves or toilet pan seals are appropriate.
– Surface water sewers – again, non-return valves and/or fallout flaps to waterways can be fitted.
– Schrijver Damp Proofing system – potentially to be removed as ineffective for creating a massive flooding vulnerability that is not outweighed by its drying effectiveness.
– Suspected suspended floor – where a sump pump is needed.
Thousands of homes better protected by flood protection work
Though they may often feel forgotten, property owners and occupiers are not fighting the good flooding fight alone; flood protection is now a growing Government priority.
Since 2015, £2.6 billion has been spent on more than 850 new flood and coastal erosion defence projects to help safeguard more than 314,000 homes, according to a March 2022 report (https://www.gov.uk/government/news/over-314000-homes-better-protected-due-to-flood-protection-work).
Some 580,000 acres of farmland, thousands of businesses, communities and infrastructure schemes, plus 5,000 miles of road have benefited; the national flood risk is officially said to have fallen by 5%.
Defra says its six year capital investment programme has also improved natural habitats. Early analysis suggests that more than £28 billion has already been saved in property and business damage; this should increase over defence asset lifetimes.
From 2021-2027, the UK’s long-term strategy will be to progressively increase protection levels as flooding and erosion take a growing toll.
Investments from 2015 to 2021 included targeted funding to accelerate regeneration in communities at high flood risk; many suffered badly from winter 2015 flooding.
The Government says it has invested more in Yorkshire and Humber than any other region since 2015 to raise protection for more than 83,000 homes; some 800 near Rochdale and Littleborough in Lancashire also benefited from £5 million invested in the River Roch Flood Alleviation scheme.
At the same time, access was improved to rivers, wildlife sites and new green spaces. Circa 12,000 acres of natural habitat were also created or improved, with 400 miles of river enhanced.
Devils in the detail – here if you need us
What we have covered above are some of the basic aspects of property level flood protection. In many cases, more detailed follow-on examinations and actions will be needed.
To create individual bespoke solutions, Enzygo’s comprehensive environmental services integrate in-depth environmental audits and environmental impact assessments (EIA), planning practice guidance, environmental management systems, advice on environmental permitting regulations, ground investigations, traffic surveys, tree surveys, landscape management and noise assessments.
With this in mind, if you would like more information on any of the issues discussed, or to talk about individual site problems, please feel free to contact us directly.
Scott Dawson, Principal Consultant, Enzygo Ltd
See the LinkedIn article – https://www.linkedin.com/pulse/property-flood-protection-two-good-reasons-early-planning-/