As flood science experts, we instinctively feel that putting flood resilience measures in place has to be an effective method of reducing losses due to flood – to say nothing of their benefit to homeowners. Research conducted by JBA now provides the re/insurance industry with more data to back up our faith in these measures. It shows how Flood Re’s Build Back Better scheme can offer a practical and cost-effective way to reduce future residential flood losses in a changing climate.
Analysis of data provided by JBA’s UK Flood Model shows that an increase in losses caused by all flood types (river, surface water and coastal) is expected as climate change leads to sea levels rising around the UK coast and more intense rainfall events. With this analysis, it is estimated that the cost of a 200-year flood event could escalate by 42% to £8.4 billion by the middle of the century if no action is taken to reduce greenhouse gas emissions. Overall, average annual losses to residential properties could soar by 87%. It’s no wonder the industry is looking to resilience measures to ameliorate the worst of these impacts.
Resistance measures such as flood and coastal defences which can reduce the extent of flooding have seen a £2.6 billion investment since 2015 protecting 314,000 properties, with a further £5.2 billion investment scheduled over the next six years (DEFRA, 2022). However, despite 251,000 new homes having been built on floodplains between 2001 and 2015, there has been only small-scale adoption of property flood resilience (PFR) measures (Sayers et al., 2015).
Flood Re’s Build Back Better initiative provides a betterment allowance of up to £10,000, enabling the rebuilding of flood-affected properties to a more flood resistant state. Uptake of this scheme by insurers is gathering pace, and the early findings of its potential impacts are very positive, with methods ranging from doorway flood barriers and airbrick covers to installing water pumps and raising electrical equipment, all enabling homeowners to better protect their homes from future flood events.
JBA has modelled PFR across Britain’s residential properties to evaluate the efficacy of this incentive at mitigating potential increases in residential flood loss under different climate scenarios.
How we did it
To model PFR, JBA used its residential insured properties stock portfolio of Great Britain – approximately 28 million properties with a total insured value (TIV) of £6.2 trillion – to analyse two distinct damage functions:
- The ‘normal house’ vulnerability, which represents a generic residential property with no PFR measures.
- The ‘adapted house’ vulnerability, which has reduced damage ratios at depths where PFR measures are effective and represents residential properties with a full suite of resistant and resilient measures (Kreibich et al., 2005).
We ran each of the two PFR vulnerability functions against the JBA catastrophe model simulating the flood risk under the current climate condition (baseline) and for two future climate scenarios (RCP4.5 – an intermediate level of warming - and RCP8.5 – unmitigated warming), as illustrated in Figure 1.
Figure 1: Workflow describes the method followed to produce the results
After a number of basic assumptions were made, the average annual loss (AAL) was extracted by postcode area for all flood types, and postcode areas ranked by AAL. A range of PFR uptake scenarios were generated and results investigated to determine the residential AAL under these different scenarios.
What this tells us
Compared to losses observed using the baseline event set, and without any PFR uptake, a £350 million (72%) increase in residential AAL is observed under the RCP4.5 scenario for 2050, while the RCP8.5 scenario shows a loss increase of £422 million (87%).
When the different levels of PFR uptake are taken into account, a large reduction in AAL is observed – even at just a 5% uptake (see Figure 2). Implementation of PFR measures would need to occur at 240,000 properties to mitigate the expected increase of residential property damage under the RCP4.5 2050 scenario, while under an RCP8.5 scenario, 320,000 properties would need these extra measures. Although these numbers seem large, this equates to just 3% (RCP4.5) or 4.1% (RCP8.5) of at-risk residential properties in Great Britain.
Figure 2: Average Annual Loss (hundreds of millions [£]) for all climate scenarios under different PFR uptake scenarios. Intersection points show which uptake scenarios generated losses below baseline levels.
What's next?
These analyses demonstrate that property flood resilience measures are effective at reducing flood loss and represent value for money, with the scheme becoming beneficial after around seven years under both scenarios (see Table 1).
Table 1: RCP4.5: 10% PFR uptake scenario. RCP8.5: 15% PFR uptake scenario. (The respective PFR uptake scenarios reduced AAL to below baseline levels.). *Assumes that £10,000 is spent on all PFR-adapted homes.
It is unlikely that all homeowners would incorporate the full set of resilience measures needed for their house to qualify for the ‘adapted house’ label. But even if only the top 5% of most ‘at-risk’ properties employed the full range of PFR measures, this would still result in a 33% reduction of AAL.
This initial study highlights the potential benefits of PFR and demonstrates how incentives such as Flood Re’s Build Back Better can provide a cost-effective method of reducing future residential flood loss. It also highlights that further study on this topic is needed, including exploring different types of adapted properties and different climate scenarios.
Get in touch to find out more about this project, or to talk to us about JBA’s UK Climate Change Flood Model and our Flood Data for every location worldwide, baseline and future risk.
Visit Flood Re for more information on the Build Back Better initiative.
References
DEFRA. 2022. Six-year programme of flood protection work exceeds targets after £2.6 billion investment. [online] Available at: https://deframedia.blog.gov.uk/2022/04/12/six-year-programme-of-flood-protection-work-exceeds-targets-after-2-6-billion-investment/ [Accessed 6 January 2023]
Kreibich, H., Thieken, A.H., Petrow, Th., Muller, M. and Merz, B. 2015. Flood loss reduction of private households due to building precautionary measures – lessons learned from the Elbe flood in August 2002. Naonltural Hazards and Earth System Sciences. [online] Available at: https://nhess.copernicus.org/articles/5/117/2005/nhess-5-117-2005.pdf [Accessed 6 January 2023]
Sayers, P.B., Horritt, M., Penning-Rowsell, E. and McKenzie, A. 2015. Climate Change Risk Assessment 2017: Projections of future flood risk in the UK. Research undertaken by Sayers and Partners on behalf of the Committee on Climate Change. Published by Committee on Climate Change, London.