How to include other contributions to overall damage costs

During a typical flood event there will be other factors affecting the overall cost impact to properties in addition to the property flood damage cost. The Damage Calculator allows you to include selected additional damages related to property flooding. These additional components have been taken from the guidance set out by the Flood Hazard Research Centre (FHRC), who are part of the University of Middlesex, UK (https://www.mdx.ac.uk/our-research/centres/flood-hazard ). Their research is published as the UK Multi-Coloured Manual (MCM) (https://www.mcm-online.co.uk/ )

The following table details the categories of additional damage available in the tool:

Each of these four additional damages are calculated as separate damage figures against each (applicable) property and as an overall total for each dataset analysed, e.g. total vehicle damage for 1% AEP, 2050 scenario event. If multiple input datasets are specified, then the additional damage totals will also have AAD and PVD values calculated. These data will be included in the summary spreadsheet that can be exported from Damage Calculator (using the “View Summaries” button).
The Settings tab provides the options to affect each of the additional damage calculations:

Vehicle damages

Vehicle damage is calculated using the following equation:

This calculation requires four settings:

• Vehicles per property: Default value is 1.15. This can be edited, value must be numeric and >=0 (setting a zero value will exclude vehicle damage from the damage analysis).

• Assumed vehicle value: Default value £3100. This can be edited, value must be numeric and >=0 (setting a zero value is another option to exclude vehicle damage from the damage analysis).

• Vehicle flooding threshold: Default value is 0.35m (this represents half a typical wheel height). This can be edited, value must be numeric and >=0.

• Use property threshold checkbox: This is unticked by default, which means if flood depth is >= vehicle flooding threshold then there is also vehicle damage. If this option is ticked, then check becomes is [flood depth – property threshold] >= vehicle flooding threshold. Note that property threshold can come from Settings tab or from property dataset attribute (latter overrides former).

Indirect damages to non-residential properties

Indirect damages to non-residential properties values are calculated with the following equation:

This calculation requires one setting:

• Indirect damage % uplift: Default value is 3% (i.e. indirect factor is 0.03). This can be edited, value must be numeric and >=0 (setting a zero value will exclude these indirect damages from the damage analysis).

Note: If PVD capping is unticked, then total indirect damage will be calculated from the uncapped PVD totals. Furthermore, if your analysis excludes calculation of PVD, then indirect damage will be calculated from the AAD totals.

Emergency response and recovery costs

Emergency response and recovery costs are calculated with the following equation:

This calculation requires one setting:

• Emergency response uplift %: Default value is 5.6% (i.e. emergency uplift factor is 0.056). This can be edited, value must be numeric and >=0 (setting a zero value will exclude all emergency response and recovery costs from the damage analysis).

Note: If PVD capping is unticked, then emergency response and recovery costs will be calculated from the uncapped PVD totals. Furthermore, if your analysis excludes calculation of PVD, then emergency response cost will be calculated from the AAD totals.

Evacuation and relocation costs for residential properties

Evacuation and relocation costs are calculated using the following method:

Thus, flood depth must be >0 to have any evacuation costs. Also, no interpolation is performed as costs are fixed for all depths in each specified range (in EvacuationCosts.csv).

For each specified scenario, the evacuation values for each property are combined to calculate an AAD value. If your analysis is not calculating PVD, then evacuation cost AAD values are summed for all properties to get a total evacuation cost AAD figure. This is then reported in the summary data for the analysis.

If your analysis includes PVD calculation, then an evacuation cost PVD value will also be calculated separately for each property and then summed to determine the total evacuation cost PVD value. This total is then reported in the summary data for the analysis.

Mental Health costs for residential properties

Mental Health costs are calculated using the following method:

Thus, flood depth must be > 0 to have any mental health costs. Also, no interpolation is performed as costs are fixed for all depths in each specified range (in MentalHealthCosts.csv).

For each specified scenario, the mental health costs for each property are combined to calculate an AAD value. If your analysis is not calculating PVD, then mental cost AAD values are summed for all properties to get a total mental health cost AAD figure. This is then reported in the summary data for the analysis.

If your analysis includes PVD calculation, then a mental health cost PVD value will also be calculated separately for each property and then summed to determine the total mental health cost PVD value. This total is then reported in the summary data for the analysis.

Capping and Write-off for Additional Damages

If you are calculating damages, and thus PVD data, for multiple scenarios and applying capping, then the tool also allows you to cap the additional damage data calculated. Additional damages are capped in a different way to property damages. Damage calculator offers two capping options for these additional damages. These are referred to as capping to market value and write-off:

• Capping to market value – for each property the tool determines the year at which property damage equals or exceeds the specified market value. Then for each additional damage the PVD is the sum of discounted additional damages up to this capping year.
• Write-off at specified AEP – write-off will be deemed to occur at scenario if there is property damage at a specified AEP (or at a more frequent AEP) in that scenario. This option requires an additional setting to be provided that specifies this AEP limit (default is 33.3%). The tool will determine if write-off has occurred for each property and then the subsequent additional damage PVD values are calculated as the sum of discounted additional damages up to the write-off year.

You can select any combination of capping method for your additional damages. The tool will report totals using both methods if requested, i.e. check which method caps the earliest for each property and apply that (this is the default setting). Alternatively, you can turn-off capping of these data (by unticking both boxes).

These settings are defined in the interface, below the other additional damages specifications, as shown below: