Navigating climate uncertainty: Strategic planning with imperfect data
by Sam Gill
When considering how prepared you are for flooding, one often overlooked factor is that in the UK, businesses and householders have a responsibility to manage flood risk to their property, and to mitigate water entering and causing damage.
In addition, there is a shortfall of resource available to support flood risk management partnerships. The capital funding in England has been doubled to £5.2bn for a six year period to 2027, however, due to cost pressures the forecast spending commitment for new flood defence projects has been cut by 40%.
Simply, there isn’t enough capital funding to protect everyone.
The lack of capital funding also presents a challenge in maintaining the condition of existing flood protection measures to their desired standard. This ultimately increases the risk of failure of these assets, which is likely exacerbated by the changing climate, causing the extreme rainfall and flooding experienced in recent years.
There is often complacency where flood protection measures have been implemented. Several high-profile flood protection schemes have had their design capacity exceeded, for example at Brechin, Scotland, in 2023 – the design standard of defences was for a 0.5% annual exceedance probability event (1-in-200 years) and this was exceeded seven years after completion of the scheme. Despite being accurately forecast to overtop the defences, several residents did not evacuate and subsequently had to be rescued by emergency services.
Therefore, understanding residual flood risk is vital to ensuring property owners and businesses can proactively mitigate flooding impacts, build back better following flooding (incorporating flood resistant material and design) and be adaptable to the uncertainty of a changing climate and the associated extreme weather events.
Current scientific observations of flood risk
There is growing evidence that previous estimates of future extreme rainfall have been underestimated. A recent scientific paper in the Journal of Climate has demonstrated there has been an observed actual increase of 8% in rainfall intensity and an increase in frequency of extreme events of between 18% - 30%. The previous estimates were 7% and 12% respectively for every one degree Celsius of warming.
This is further supported by recently released research from the James Hutton Institute, commissioned by the Scottish Government, that has concluded ‘February and April have become up to 60 percent wetter in the last 30 years, particularly in the west, compared with the previous three decades. That exceeds the projected change for 2050 which was expected to see around 45-55 percent more rain’.
Do you know your own flood risk?
There is an abundance of information and resources available to assist in improving flood preparedness. The UK has online flood mapping that is easily accessible. The links below are a good starting point to assess your flood risk.
Northern Ireland: Flood Maps NI | Department for Infrastructure (infrastructure-ni.gov.uk)
It should be noted that due to the strategic nature of the flood mapping undertaken to inform these datasets and maps, it is inevitable that the flood mapping will have inherent uncertainty. Nevertheless, it is a sound starting point to understand your flood risk. If you are within a flood risk area or in close proximity, consideration should be given to the local hydraulics that may impact flood risk and whether you need specialist flood risk advice.
Have you got a flood plan?
Has the flood plan been created, reviewed, and regularly tested, detailing procedures, evacuation routes, meeting points and an action list to ensure you are prepared to mitigate flooding and provide safe evacuation. Have you serviced and maintained any flood mitigation equipment (pumps, gates, door guards etc…)
Flood plans are tailored at an individual, community, or business level. For more advice on preparation, visit: Prepare for flooding: Protect yourself from future flooding - GOV.UK
Alongside the Met Office’s weather warning system, throughout the UK there are flood warning services that are free to sign up to. They can provide wider area alerts as well as targeted warnings for some specific areas. There are also several commercially available solutions that can be installed to provide local water level monitoring; these are particularly beneficial for small watercourses or sites that require specific notification of water levels to enact their flood plan.
If you are notified of a flood warning (when flooding is expected), you should:
Recovery from flooding
The recovery time from flooding is typically measured in months to years. This can be because of contamination of buildings, due to flood water being mixed with sewage, and the subsequent drying out process. The repair and restoration work can also be a lengthy process, particularly if a number of properties locally are affected and resources for repairing properties are stretched. If you are impacted by flooding, you should speak to your insurance company as soon as practically possible, take photos of damages, and record the depth of flooding experienced.
Improve your understanding of flood risk
With the observed increase in extreme events, a detailed, site-specific, flood risk assessment, which could include hydraulic modelling, can be a vital tool for flood risk managers, property owners and businesses. Hydraulic modelling provides detailed information to inform the assessment of flood risk for the likely lifetime of any development. It also supports the decision making process to design mitigation at a site level, that can’t necessarily be provided from existing strategic flood mapping.
Site specific hydraulic modelling outputs are used to:
For new developments, consideration of flooding and changing climate should be considered early in the project life cycle to give proper consideration of the associated risk and uncertainties. With the information we have now, there is an opportunity to embed climate adaptability into the design process, enhancing and protecting development into the future.
For existing areas, understanding the current and future risk of flooding can be used to inform a resilience and adaptation strategy to mitigate the effects of a changing climate and prioritise investments.
SLR’s team of Flood Risk Consultants and Hydrologists can support your flood risk understanding and mitigation. Get in touch with us today to learn more about our hydrology services, and for a conversation about your site or project.