Guidance

Frequently flooded properties and write-off in FCERM appraisal

Published 1 April 2026

Applies to England

1. Purpose 

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

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

• sections 10.7.4 and 10.7.5 of the Appraisal Technical Guidance 
• section 4 of the FCERM grant-in-aid: discount rates, price indices and capping supplementary guidance 

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

2. Household responses to flood risk 

2.1 Rationale 

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

This is often supported by: 

• insurance payouts  
• recovery grants administered by local authorities 

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

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

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

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

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

• have experienced flooding before  
• take sensible damage reducing actions 

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

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

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

2.2 Detailed approach 

The details of the new approach are listed below: 

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

2.3 Damage limiting tables 

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

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

Table 1 – Property Annual Average Damage (AAD) reduction factors by onset of flooding 

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 evacuation and temporary accommodation by the factors in Table 2. 

Table 2 – Evacuation Annual Average Damage (AAD) reduction factors by onset of flooding 

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

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

In this case, you should reduce: 

• the property AAD damages to £1,580, using the 0.79 coefficient  
• the evacuation AAD to £150 using the 0.75 coefficient

2.4 Other considerations 

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

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

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

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

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

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

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

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

3. Supporting Bibliography 

• Clarke, J., McConkey, A., Samuel, C., & Wicks, J. (2015). Quantifying the benefits of flood risk management actions and advice: Flood incident management and property level responses (SC090039/R). Environment Agency. 
• Department for Environment, Food and Rural Affairs (2023). Evaluation of Property Flood Resilience Repair Grant Scheme. 
• Entec UK & Greenstreet Berman (2008). 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. 
• Foley, J. (2023). Building back better and mainstreaming property flood resilience. Environment Agency Blog. Available at: https://environmentagency.blog.gov.uk/2023/05/22/building-back-better-and-mainstreaming-property-flood-resilience/ 
• Grothmann, T. and Reusswig, F. (2006). People at risk of flooding: Why some residents take precautionary action while others do not. Natural Hazards, 38(1–2), pp. 101–120. Available at: https://link.springer.com/article/10.1007/s11069-005-8604-6 
• Harries, T. (2012). The anticipated emotional consequences of adaptive behaviour: Impacts on the take-up of household flood-protection measures. Environment and Planning A, 44(3), 649–668. 
• Jacobs (2019). Long Term Investment Scenarios: Additional Analysis, Topic 5 technical report Property level resistance and resilience. Environment Agency. 
• Kreibich, H., Thieken, A. H., Petrow, T., Müller, M., & Merz, B. (2005). Flood loss reduction of private households due to building precautionary measures – lessons learned from the Elbe flood in August 2002. Natural Hazards and Earth System Sciences, 5(1), 117–126. 
• May, P. & Chatterton, J. (2012). Establishing the cost effectiveness of property flood protection: Technical report (FD2657). Department for Environment, Food & Rural Affairs (Defra). 
• Osberghaus, Daniel (2017). The effect of flood experience on household mitigation—Evidence from longitudinal and insurance data. Global Environmental Change, Volume 43, March 2017, Pages 126-136. 
• Park, T., Oakley, M., & Luptakova, V. (2020). Applying behavioural insights to property flood resilience (Project No. FRS17191). Environment Agency. 
• Parker Tunstall and Mccarthy (2007). New insights into the benefits of flood warnings: Results from a household survey in England and Wales. Environmental Hazards, 7 (3) 193-210 
• Poussin, J.K., Botzen, W.J.W., & Aerts, J.C.J.H. (2015). Effectiveness of flood damage mitigation measures: Empirical evidence from French flood disasters. Global Environmental Change, 31, 74–84. 
• Priest and Parker (2012). Investigation of the Relationship between Flood Warning Lead Time and Flood Warning Response. Report for Environment Agency Evidence Project SC090039 Stage 2 
• Qa Research Ltd. (2024). Public Flood Survey 2023-24 Full Report. Environment Agency 
• Scolobig, A., Borga, M., & Fuchs, S. (2020). Multiple flood experiences and social resilience. Findings from Three Surveys on Households and Companies Exposed to the 2013 Flood in Germany. Weather, Climate, and Society, 12(1), 1–13. 
• Thistlethwaite, J., Henstra, D., Brown, C., & Scott, D. (2018). How flood experience and risk perception influences protective actions and behaviours among Canadian homeowners. Environmental Management, 61(2), 197–208. https://doi.org/10.1007/s00267-017-0969-2 
• Osberghaus, Daniel (2014). The determinants of private flood mitigation measures in Germany. Ecological Economics, Volume 110, pp. 36-50.