扒哥吃瓜

Skip to main content
Guidance

Frequently flooded properties and write-off in FCERM appraisal

Published 1 April 2026

Applies to England

漏 Crown copyright 2026

This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk.

Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.

This publication is available at /government/publications/fcerm-grant-in-aid-frequently-flooded-properties-and-write-off-in-appraisal/frequently-flooded-properties-and-write-off-in-fcerm-appraisal

1. Purpose听

Following a flood, residents typically repair their properties and, where possible,听replace damaged听possessions. Many will also听take听sensible precautions to limit the impact of听future floods. This听guidance explains how听you should account for these听responses in听properties听with听very high听risk of flooding. It also explains听how to account for permanent abandonment of properties for very severe flooding听and coastal erosion.听听

This听document听supersedes听previous听guidance on capping and write-off. This includes the approaches set out in:听

This approach is intended for detailed appraisals听informed by听depth damages and producing their own Annual Average Damages (AAD).

2. Household responses to flood risk听

2.1 Rationale听

The principle of this听new approach听is that people will continue to live in a home at risk of frequent flooding. After each flood they will听refurbish听and replace听possessions.听听

This is often supported by:听

  • insurance payouts听听
  • recovery grants administered by local authorities听

It is听very rare听for properties听to be abandoned due to flood impacts. This is often referred to in FCRM appraisal guidance as 鈥榳rite off鈥�.听This occurs when听the risk is such that even if formal resistance and resilience measures were installed, the home would not be听habitable.听Section听3.2听of this guidance provides the formal definition for assessing if property is habitable.听听听

The aim is to听better reflect observed household behaviour听in the听appraisal听process. These behaviours include:听

  • the effect听of actions to reduce the impacts of future floods, such as听resilient听repair听
  • learned behaviours following past flooding experiences which further reduce damages听听

Under this approach,听we no longer cap听property damages at regional market听prices.听

This means that听we assume听that听if a property is at risk from very frequent floods听the homeowner will:听

  • have experienced flooding before听听
  • take sensible damage reducing actions听

However, this approach does not go as far as to include formal property resistance and resilience measures. This includes those听installed with a formal resistance and resilience scheme.听听

Formal resistance and resilience measures would be part of a risk mitigation option. The benefits of those measures must be available compared to听a baseline scenario听without a formal scheme.听听

Instead, this听approach is informed by听uptake听of听various build back better measures and simple adaptation behaviours.听These are linked to flood experience using probability of flooding听and typical number of years in a home.

2.2 Detailed听approach听

The details of the听new approach听are listed below:听

  • all properties听which听flood above floor level听less听frequently听than 1:10听Annual Exceedance Probability (AEP)听collect damages听in accordance with听the听Multicoloured Manual (MCM)听depth damage tables听
  • once a property is at risk of above floor level flooding in a 1:10听AEP听and more frequent, the Annual Average Damages (AADs) are reduced by a factor听鈥� this is shown in听table 1听- note听that听the AAD is reduced by the factor, not the event damages听
  • where听appropriate, flood frequency should reflect the combined effect of multiple sources of flood risk, with damage reduction factors applied across all听sources听
  • damage听reduction factors听are applied听equally听across听all听property types听independently of听age,听type听or social class听
  • in the absence of better evidence,听you should apply the same damage reduction coefficients to听non-residential properties as those developed for residential properties听
  • practitioners should review property types in areas with frequent flooding and consider re-categorising them where non-standard building designs or adaptations significantly reduce vulnerability听听
  • a听maximum of one flood per year is assumed as it may take a year to repair the property听鈥� this means you should not include damages more frequent than once per year when you calculate听the AADs.听In practice the threshold of flooding may be much less frequent, and听you should听determine听this听from modelling outputs听or by considering past events听
  • if a property is at risk of internal flood depths >60cm1听in a听1:2听AEP听event听(if this has not been modelled then you can use a 1:3听AEP听event), then it is written off at the听regional听average property price for that property type听
  • if a property is at risk of permanent inundation above floor level, then it is written-off at the听regional听average market value for that property type听- if this property has upstairs dwellings (flats) then the upstairs flats would also be written off at the same time听
  • repeated shallow flooding, such as from a spring tide, would not incur write-off as the property should be adaptable to this type of flooding听
  • properties at risk of erosion will continue to be assumed to be lost in the year they are unsafe听using听regional听average听prices听for each property type听
  • business disruption damages will continue to be based on a听percentage听of the non-residential property damages,听after听you apply听the听damage limiting听factors听
  • you should continue to include mental health damages听in accordance with听existing听supplementary guidance听- however, as these losses include 2 years of听impacts already,听you should not apply听mental health damages more听frequently听than in a 1:2 event听
  • evacuation and temporary accommodation 鈥撎齧ore resilient buildings will reduce recovery time, which means you must reduce听temporary accommodation听annual average damages听by the relevant factor听鈥� this is shown in听Table 2听
  • you should continue to听accrue听other听property related听damages including听intangible impacts, vehicular and risk to life without any reductions

2.3 Damage limiting tables听

If听properties听experience internal flooding at a frequency of听1:10听AEP or more听often, you must听apply the following damage reducing factors to their听property听direct damage AADs.听This is in line with the approach set out in section听2.2.听

We have based these results听on听a literature review of flood resilience and adaptation for residential properties.听The听remaining data gaps听are听addressed through conservative assumptions informed by expert judgement.听

Table 1 鈥� Property Annual Average Damage (AAD) reduction factors by听onset of flooding听

1 in 10 AEP 1 in 5 AEP 1 in 2 AEP
0.88 0.79 0.71

You should reduce annual average damages for听evacuation and temporary accommodation听by the factors in Table 2.听

Table 2 鈥� Evacuation Annual Average Damage (AAD) reduction factors by听onset of flooding听

1 in 10 AEP 1 in 5 AEP 1 in 2 AEP
0.88 0.75 0.64

For example, a home floods听above floor level in a 1 in 5 AEP event听but听remains听dry听in听a 1 in听2 AEP event. The听AAD property damages听are听拢2,000 and evacuation damages听are听AAD 拢200.听听

In this case,听you should reduce:听

  • the property听AAD听damages to 拢1,580, using the 0.79 coefficient听听
  • the evacuation AAD to 拢150听using the 0.75听coefficient

2.4 Other considerations听

You should always听check听your听top听receptors听of听damages听and confirm that the results听produced听are sensible.听Pay particular attention to听non-residential properties听with large floor areas. Under the听new approach,听businesses听could repeatedly receive flooding below 60cm听building up听damages听that may not reflect听likely real-world听outcomes and behaviours.听听

In these circumstances,听occupying business would be expected to move听or adapt. The property may听be left听empty听or a听more听resilient business听could move in. You should discuss these properties in the听economics听appendix听accompanying听a听business case. You should also justify the approach you have taken.听If the risk of flooding is already extremely frequent, then these actions may already have happened.听听

If a听permanent听property has a听particularly听water sensitive form of construction, it听may not tolerate flooding to the same extent as听typical听properties. In听such听cases,听it may not be reasonable to assume听a听property is habitable听up to a depth of flooding of 60cm in a 1:2-year event. In these circumstances听you can听use the听regional听write-off value. You should听justify this in听your听accompanying听economics听appendix.听听

The households鈥� response听included in this analysis do not听require a听flood warning. There is therefore no double counting between flood warning benefits and the damage reduction associated to Table 1 and Table 2.听听

The damage听reducing factors听were developed using evidence from听residential property. Applying these to听non-residential property听is an assumption that would听benefit听from further research.听

The damage reducing factors should not be applied to the MCM鈥檚 Weighted Annual Average Damages (WAAD):听

  • The WAAD is derived from听a听limited听record of听historical flood events听and听is听composed of comparatively shallow flood depths.听It听can therefore underestimate damages听in some circumstances听

Given the above, applying听the damage reducing factors to the WAAD听risks听exacerbating听this听issue.

3. Supporting Bibliography听

  • Clarke, J., McConkey, A., Samuel, C., & Wicks, J.听(2015).听Quantifying the benefits of flood risk management actions and advice: Flood incident management and property level responses听(SC090039/R). Environment Agency.听
  • Department for Environment, Food and Rural Affairs (2023).听Evaluation of Property Flood Resilience Repair Grant Scheme.听
  • Entec听UK & Greenstreet Berman听(2008).听Developing the evidence base for flood resistance and resilience: Technical Summary FD2607. Joint Defra/Environment Agency Flood and Coastal Erosion Risk Management Research and Development Programme.听
  • Foley, J.听(2023). Building back better and mainstreaming property flood resilience.听Environment Agency Blog. Available at:听听
  • Grothmann, T.听and听Reusswig, F.听(2006). People at risk of flooding: Why some residents take precautionary action while others do not.听Natural Hazards, 38(1鈥�2), pp. 101鈥�120. Available at:听听
  • Harries, T.听(2012). The听anticipated听emotional consequences of adaptive behaviour: Impacts on the take-up of household flood-protection measures.听Environment and Planning A, 44(3), 649鈥�668.听
  • Jacobs听(2019).听Long Term Investment Scenarios: Additional Analysis, Topic 5 technical report Property level听resistance听and resilience. Environment Agency.听
  • Kreibich, H., Thieken, A. H., Petrow, T., M眉ller, M., & Merz, B.听(2005). Flood loss reduction of private households due to building precautionary measures 鈥� lessons learned from the Elbe flood in August 2002.听Natural Hazards and Earth System Sciences, 5(1), 117鈥�126.听
  • May, P. & Chatterton, J.听(2012).听Establishing the cost effectiveness of property flood protection: Technical report (FD2657). Department for Environment, Food & Rural Affairs (Defra).听
  • Osberghaus,听Daniel听(2017).听The effect of flood experience on household mitigation鈥擡vidence from longitudinal and insurance data.听Global Environmental Change, Volume 43, March 2017, Pages 126-136.听
  • Park, T., Oakley, M., &听Luptakova, V.听(2020).听Applying behavioural insights to property flood resilience听(Project No. FRS17191). Environment Agency.听
  • Parker Tunstall and听Mccarthy听(2007).听New insights into the benefits of flood warnings: Results from a household survey in England and Wales.听Environmental Hazards, 7 (3) 193-210听
  • Poussin, J.K.,听Botzen, W.J.W., & Aerts, J.C.J.H.听(2015). Effectiveness of flood damage mitigation measures: Empirical evidence from French flood disasters.听Global Environmental Change, 31, 74鈥�84.听
  • Priest and Parker听(2012).听Investigation of the Relationship between Flood Warning Lead Time and Flood Warning Response.听Report for Environment Agency Evidence Project SC090039 Stage 2听
  • Qa听Research Ltd. (2024).听Public Flood Survey 2023-24 Full Report.听Environment Agency听
  • Scolobig, A., Borga, M., & Fuchs, S.听(2020).听Multiple flood experiences and social resilience.听Findings from Three Surveys on Households and Companies Exposed to the 2013 Flood in Germany.听Weather, Climate, and Society, 12(1), 1鈥�13.听
  • Thistlethwaite, J.,听Henstra, D., Brown, C., & Scott, D.听(2018).听How flood experience and risk听perception听influences protective actions and behaviours among Canadian homeowners.听Environmental Management, 61(2), 197鈥�208.听听
  • Osberghaus, Daniel听(2014).听The determinants of private flood mitigation measures in Germany. Ecological Economics, Volume 110, pp. 36-50.
Back to top