Guidance

Understanding the properties benefitting metric

Published 22 June 2026

Applies to England

1. Introduction

When you submit a project opportunity, you will need to record your estimate of the number of properties that will benefit from your project.

The properties benefitting metric is the number of residential and non-residential properties benefitting from flood and coastal erosion risk investment. The metric is based on the impact of an investment on present day flood probability or coastal erosion risk.

You should report the properties benefitting metric for projects that either:

• prevent an increase in flood probability or coastal erosion risk by refurbishment or replacement of existing assets
• reduce flood probability or coastal erosion risk through new or improved defences, or other measures such as natural flood management (NFM)

You should report the number of properties benefitting by assigning each property to one of the 6 metrics below. You must only count each property once.

• OM:2.1 - Number of properties benefitting from investment to prevent an increase in the probability of flooding
• OM:2.2 - Number of properties benefitting from a reduction in the probability of flooding by 50% or more
• OM:2.3 - Number of properties benefitting from a reduction in the probability of flooding by less than 50%
• OM:2.4 - Number of properties benefitting from new individual property flood resilience measures
• OM:3.1 - Number of properties benefitting from investment to prevent an increase in coastal erosion risk
• OM:3.2 - Number of properties benefitting from investment to reduce coastal erosion risk

The sum of the 6 metrics is the total number of properties benefitting from the investment.

If your project is standalone NFM, you should report properties under OM:2.3 or OM:3.2

2. Properties that can be counted as properties benefitting

A benefitting property must be an existing residential or non-residential building that benefits from the flood or coastal erosion risk investment. This includes those built after 2012.

For projects managing flood risk, properties may benefit from investment if the project results in either:

• the prevention of an increase in the likelihood of flooding
• a reduction in the likelihood of flooding
• a reduction in the depth of flood water

This can include flooding below the height of the property threshold, as shallow flooding can still cause damage to buildings. If flooding or coastal erosion impacts the ground floor of a block of flats or an apartment building, you can also count upper floor flats as properties benefitting.

For coastal erosion projects, a property benefitting must have either:

• been prevented from becoming unsafe due to coastal erosion
• had permanent loss directly avoided
• had permanent loss managed to enable adaptation to coastal erosion.

For projects managing either flood risk or coastal erosion, you should not count:

• properties that are planned but not yet constructed
• properties that are temporary and do not have an address
• properties where their loss from coastal erosion is not permanent
• small ancillary buildings, such as garden sheds
• other unclassified buildings defined by the National Receptor Dataset (NRD)
• properties affected by loss of services or access only

3. Developing the number of properties benefitting

When you are submitting a proposal for a new project, you should make estimates of properties benefitting based on the information you have available. Methods for making these estimates are described in Defining which areas and properties benefit from investment. You can then refine and improve these estimates as the project progresses and more information about the benefits of the investment become clear.

Through all the stages of your project, you should avoid undertaking new modelling to support properties benefitting counts alone. Use the best information that your project has available to produce your properties benefitting count. Understanding the total number of properties benefitting is the most important outcome. In particular, you should use proportionate methods to estimate whether the level of flood risk reduction is more or less than 50%.

4. National Receptor Dataset

The National Receptor Dataset (NRD) is a property dataset used to identify risk receptors in England. These include:

• homes
• commercial buildings
• schools
• hospitals

The dataset uses property classifications from the Ordnance Survey and aligns them with the multi-coloured handbook to support the economic appraisal of projects.

You can use the National Receptor Dataset (Partner Version) to count the number of properties that would benefit from your flood risk project. You must be a member of the Public Sector Geospatial Agreement (PSGA) and be logged into the Defra Data Services Platform to access the National Receptor Dataset. If you are not a member of the PSGA and are not logged in the link will not work.

If you cannot access the NRD, other methods of counting properties are described in Defining which areas and properties benefit from investment.

5. Properties Benefitting OM:2.1

Metric OM:2.1 is the number of properties benefitting from investment that prevents an increase in the probability of flooding. You should report properties benefitting from asset refurbishment or asset replacement projects under this metric.

The capital grant eligibility supplementary information provides more details on project definitions and types.

Sustaining the standard of service on existing assets rarely offers a chance for extending benefits towards managing risks from other sources. To keep assessments proportionate, you can often use existing information and apportionment principles to calculate properties benefitting rather than undertaking project specific modelling.

Sources of existing information can include:

• asset management plans
• previous business cases
• existing modelling outputs (local or national)
• strategic studies
• local knowledge

Apportionment is likely to be required when:

• multiple assets contribute to reducing risk in the same area
• multiple projects occur over time
• more than one source of risk exists
• the asset is part of a wider system

You should apportion benefits and outcomes across all assets in an asset management system when making the case for investment. You should avoid disproportionate claims of properties benefitting which would disadvantage sustaining the overall standard of service in the wider asset management system and over time. The goal is to ensure benefits are distributed fairly across the asset system and not concentrated disproportionately on a single project.

6. Properties Benefitting OM:2.2 and OM:2.3

Metric OM:2.2 and metric OM:2.3 are the number of properties benefitting from a reduction in the probability of flooding resulting from:

• new defences
• improving the standard of service of existing defences

Metric OM:2.2 is the number of properties benefitting from a reduction in the probability of flooding by 50% or more. Metric OM:2.3 is the number of properties benefitting from a reduction in the probability of flooding by less than 50%.

These metrics exclude properties benefitting from new property flood resilience measures.

For standalone NFM or sustainable drainage (SuDS) projects, you should assume that the level of flood risk reduction is less than 50% and count properties under OM:2.3.

For standalone NFM projects under £3 million, you should use the method set out in Defining which areas and properties benefit from investment - GOV.UK. Use this method to calculate the number of properties contributing to the OM:2.3 metric throughout all stages of your project. Your assessment should be updated as your project is developed. 

For standalone NFM projects above £3 million and projects combining NFM with hard engineering, you should calculate the number of properties contributing to OM:2.2 and OM:2.3.

For new defence projects that need to assess the level of reduction in probability, an example is provided below: 

Example 1

A flood defence project is built to reduce risk to 75 properties. Before the investment:

• 25 properties are in an area at risk of flooding during a 5% annual exceedance probability (AEP) event (a 1 in 20-year event)
• 50 properties are in an area at risk during a 1.33% AEP event (1 in 75-year event)

The flood defence scheme protects these properties up to a 1% AEP event (1 in 100-year event).

Table 1 Example of properties benefitting from a project

Number of Properties	Annual Exceedance Probability Before	Annual Exceedance Probability After	Probability Reduction
25	5%	1%	80%
50	1.33%	1%	25%

The reported metrics of the project are:

• 25 properties benefit from a reduction in the probability of flooding by 50% or more and are counted as OM 2.2
• 50 properties benefit from a reduction in the probability of flooding by less than 50% and are counted as OM 2.3

The total number of properties benefitting is 75.

When you are submitting a proposal for a new project, it is not necessary to have a detailed understanding of the level of the reduction in probability your project will provide. You should make reasonable estimates of how many properties will fall into OM:2.2 and how many properties will fall into OM:2.3.

If your project is approved for early project development, you may need to refine your estimate for your outline or single-stage business case. The method you use to calculate the number of properties benefitting will vary depending on the data available and the type of project or intervention. You should not carry out modelling solely to determine the number of properties benefitting. Instead, your calculations should use data that has or will be used for the project’s design and appraisal.

If you have modelled scenarios, you should use the present-day risk in the do-nothing scenario to assess the probability of flooding before the investment. To assess the probability of flooding after the investment, you should choose a scenario that best reflects the probability of flooding immediately after the intervention.

If the reduction in the flood probability of a property between the 2 scenarios is more than or equal to 50%, you should report it as OM:2.2. If the reduction in flood probability is less than 50%, you should report it as OM:2.3.

If you do not have clear evidence of a reduction in flood probability, you may consider using proxies for probability change to count properties benefitting. For example, if your project only has a small set of modelled events, showing a change in flood probability of less than 50% may not be possible. There may be situations where a property remains at risk during a modelled AEP but the depth or damage of the flooding has reduced. Any claims of properties benefitting made using proxies should be reported as OM:2.3. 

Properties that only receive marginal reductions in flood risk or reductions in flood risk that could be attributed to model uncertainty should not be reported. You should not count properties that have less than 0.5% AEP before the investment.

If you are using the Surface Water Investment Model (SWIM) appraisal route, you should use the properties benefitting figure that your appraisal has developed.

7. Properties Benefitting OM:2.4

Metric OM:2.4 is the number of properties benefitting from new property flood resilience measures that increase flood resistance. These can include, but may not be limited to:

• flood doors
• flood barriers
• self-closing air bricks
• non-return valves

You should not count properties that have benefitted only from improved recoverability. Improved recoverability includes internal adaptations such as:

• tiled floors
• raised electrics
• a flood-resilient kitchen

For properties where existing individual property resilience measures are being replaced, these should be recorded as OM 2.1.

8. Properties Benefitting OM:3.1 and OM:3.2

Metrics OM:3.1 and OM:3.2 capture the delay in coastal erosion risk that properties will benefit from due to the planned package of measures for the project. You can count a property under these metrics if:

• the project prevents the property from becoming unsafe due to coastal erosion
• the property’s permanent loss is directly avoided
• permanent loss is managed to enable adaptation to coastal erosion.

You should record properties benefitting from asset refurbishment and asset replacement projects as OM 3.1. You should record properties benefitting from projects delivering new defences or adaptation measures, including NFM, as OM 3.2.

When you are submitting a proposal for a new project, you should use the National Coastal Erosion Risk Map (NCERM) to identify properties at risk of coastal erosion. You can use the map to identify properties which have the potential to benefit due to the planned package of measures for your project. The mapping can be used to identify properties which would benefit due to their current risk of:

• Medium Term Loss - Less than or equal to 30 years (1 year to 30 years). Use the Present Day 2055 scenario with No Future Intervention scenario.
• Longer term loss: Greater than 30 years (31 years to 100 years). Use the Present Day 2105 with No Future Intervention scenario.

For standalone NFM projects, you should focus on medium-term loss to calculate properties contributing to OM3.2 metric. This reflects a typical design life of around 20 years. 

If your project is approved for early project development, you may need to refine your estimate for your outline or single-stage business case. You should supplement your initial approach with expert knowledge and local analysis during project appraisal to finalise the number of properties benefitting from your project. For example, the shape of the benefit area used alongside NCERM data to count properties benefitting may be different from one project to another due to local factors. There may also be properties in front of the defence line that benefit from the investment that are not captured in the NCERM scenario.