Damage Calculator's core functionality is to calculate the economic damages caused to both residential and non-residential properties due to flooding. To calculate these damages, Damage Calculator reads flood depths from the specified 2D model results that are underlying each specified property (represented by a single point in a point shapefile). It then looks up in the relevant depth damage curve for the property type (in the chosen set of depth damage curves) to read the damage that equates to the flood depth. Damage Calculator then adds together all property damages to get the overall total of economic damages.
Damage Calculator has been developed in collaboration with 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). The approaches in the tool follow FHRC’s 2013 publication: Flood and Coastal Erosion Risk Management: A Manual for Economic Appraisal. This is more usually referred as the Multi-Coloured Manual (MCM).
To support MCM approaches, FHRC publish an annual Handbook for Economic Appraisal (usually referred to as Multi-Coloured Handbook (MCH) and updates of property depth damage data. With the appropriate licence these data can be downloaded from the website; https://www.mcm-online.co.uk/ in a format that can be used directly in Damage Calculator. Depth damage data from other sources can also be used in Damage Calculator.
The methods and underlying datasets used follow the approaches described in MCM. This allows the user to comply with the UK Environment Agency’s FCERM Appraisal Guidance that guides how the business case for flood risk management projects are developed in England.
Key Features
Damage calculator can perform several calculation types, including:
• Damages from a single flood event
• Combining multiple flood events in the same scenario to calculate annualized average damages (AAD) for an epoch
• Combining multiple results from multiple scenarios to calculate present values damages (PVD). This allows calculations to account for the quantity of flood damage changing over time
Damage Calculator calculates a range of damages caused by flooding, including:
• Direct property damages (residential and non-residential)
• Vehicle Damages
• Indirect non-residential business disruption
• Emergency Services Costs
• Evacuation Costs
• Mental Health Costs
• Risk to Life Costs
• Intangible Health Costs
Additionally to the economic damages to residential and non-residential properties, Damage Calculator can also calculate a range of additional damages caused by flooding. These additional damages include costs of emergency services and evacuation, property damages, and business disruption costs etc. All calculated damage types are described in detail in this section below.
Vehicle damages
Vehicle damages are calculated for residential properties only.
Vehicle damage calculation
If (flood depth) – [property threshold] > (vehicle flooding threshold) then
(Vehicle damage per property) = (Assumed vehicle value) * (Vehicle per property factor)
Where items denoted in square brackets are optional, and other parameters are as defined below.
Field in data entry form | Description | Details |
|---|---|---|
Vehicles / property | Average number of vehicles per property. | Default value 0.97. Setting a zero value will exclude vehicle damage from the damage analysis. |
Assumed vehicle value | Assumed average value for each vehicle. | Default value £5600. Value must be numeric and >=0. Setting a zero value is an option to exclude vehicle damage from the damage analysis. |
Vehicle flooding threshold | This value should equal half a typical wheel height. | Default value is 0.39m. Value must be numeric. Value may be <0 if required, to represent vehicles stored at a lower level than the property they are associated with. |
Combine with property threshold checkbox | If ticked, this combines the threshold of the property obtained from the property dataset to the value input in the ‘vehicle flooding threshold’ setting (see above). For example, if a property has a threshold of 10mAOD and vehicle flooding threshold is set at 0.35m, vehicle flooding would occur at a water level of 10.35mAOD. | This setting is ticked by default. |
Emergency services
Emergency Services costs are calculated for both residential and non-residential properties.
Emergency response and recovery costs equation
Emergency response cost per property = [capped property Present Value Damages (i.e. res or non-res)] x [Emergency response uplift %]
Where items denoted in square brackets are optional, and other parameters are as defined below.
Field in data entry form | Description | Details |
|---|---|---|
Emergency response uplift % | This value represents the emergency service cost. If a property suffered damages in a flood event of £10,000, then in this case, the emergency services costs would be (£10,000 * 0.056 = £560). | Default value is 5.6% (i.e. emergency uplift factor is 0.056). This value must be numeric and >=0. Setting a zero value will exclude all emergency response and recovery costs from the damage analysis. |
Indirect economic damage costs
Indirect economic damage costs are calculated for non-residential properties only.
Indirect damages to non-residential property values cost equation
Emergency response cost per property = [capped property PVD (i.e. res or non-res)] x [emergency uplift factor]
Field in data entry form | Description | Details |
|---|---|---|
Indirect damage % uplift | This value represents the indirect economic damage costs. If a property suffered damages in a flood event of £10,000, then in this case, the indirect economic damage costs would be (£10,000 * 0.03 = £300). | Default value is 3% (i.e. indirect factor is 0.03). This value must be numeric and >=0. Setting a zero value will exclude these indirect damages from the damage analysis. |
Evacuation
Evacuation Costs are calculated for residential properties only.
This calculation uses a look-up table (specified as CSV file in the depth damage data folder) to calculate cost based on property type and flood depth. If working in the UK, the example cost data included with Flood Modeller should be updated with data from the MCM.
Evacuation and relocation cost calculation
Damage calculator checks if property type is residential
If property type is residential, damage calculator looks up evacuation cost for the specified property type in EvacuationCosts.csv where: “From” depth value < property flood depth <= “To” depth value.
Flood depth must be >0 to for evacuation costs to be calculated for a given property.
It should be noted that no interpolation is performed as costs are fixed for all depths in each specified range.
Mental Health
Mental Health cost are calculated for residential properties only.
The calculation uses a look-up table (specified as CSV file in the depth damage data folder) to calculate cost based on property type and flood depth.
Cost data included with Flood Modeller originates from Environment Agency Guidance ‘Advice for Flood and Coastal Erosion Risk Management Authorities – Mental Health Costs of Flooding and Erosion’ (17/04/2020).
Mental Health cost calculation
Damage calculator checks if property type is residential
If property type is residential, damage calculator looks up mental health costs for the specified property type in MentalHealthCosts.csv where: “From” depth value < property flood depth <= “To” depth value.
Flood depth must be >0 to for mental health costs to be calculated for a given property.
It should be noted that no interpolation is performed as costs are fixed for all depths in each specified range.
Intangible health costs
Intangible Health costs are calculated for residential properties only
The calculation uses a look-up table (specified as CSV file in the depth damage data folder) to calculate cost based on property type and frequency of flooding
Cost data included with Flood Modeller originates from DeFRA report ‘R&D Technical Report FD2005/TR’.
Intangible Health cost calculation
Damage calculator checks if property type is residential
If property type is residential, damage calculator looks up intangible health costs for the specified property type in MentalHealthCosts.csv where: “From” depth value < property flood depth <= “To” depth value.
Risk To Life
Damage Calculator has an option to calculate loss of life. These calculations are undertaken on an individual property basis, and can be calculated for individual events, AAD and PVD.
The calculation method used by damage calculator is based on DeFRA guidance ‘Supplementary Note to Operating Authorities - Assessing and Valuing the Risk to Life from Flooding (May 2008).’
The Risk to Life option is activated by ticking the Calculate Risk to Life box on the Calculation Information tab. When this is ticked, two extra columns appear in the input depth grids table:
Flood Hazard Rating grid
Time of Inundation grid
Each cell in these columns contains a browse button. To enter data in these columns, click on a cell to reveal the browse button, then click this to access a file browser window. Multiple grids can be selected and added at the same time.
Note
The risk to life analysis is only available if input flood depth data is in grid format.
Calculation of Risk to Life requires the additional data inputs detailed below.
Loss of Life Reference Valuation
This is the monetary value to be assigned to the loss of each life. Typical values for use in the UK can be obtained from the Department for Transport ‘Transport Appraisal Guidance’ spreadsheet available from https://www.gov.uk/government/publications/tag-data-book. A value can be obtained from the 'Fatal Total' cell on the COBALT1 tab.
Property dataset fields
In addition to the standard fields in the property database (see Property database section), the fields below must be provided.
Field | Field Name in Damage Calculator Field Mapping | Description |
|---|---|---|
Nature of Area | natarea | This field requires a numerical value of 1, 2 or 3 to represent the nature of the area where risk to life is being calculated. The DeFRA guidance note ‘Supplementary Note to Operating Authorities - Assessing and Valuing the Risk to Life from Flooding (May 2008)’ states that the following values can be used: • 1 = low risk (e.g. multi-floor flats) • 2 = moderate risk (normal residential) • 3 = high risk (bungalows, campsites) It is recommended that users check for updated studies before undertaking an analysis. |
Flood Warning Score | fws | This field requires the input of a numerical Flood Warning Score. The DeFRA guidance note ‘Supplementary Note to Operating Authorities - Assessing and Valuing the Risk to Life from Flooding (May 2008)’ states that the following values can be used: • 2.15 (England) • 2.23 (Wales) It is recommended that users check for updated studies before undertaking an analysis. |
% infirm | infirm | This field requires a numerical input greater than or equal to 0 and less than or equal to 100, representing the percentage of residents suffering from a long-term illness. If working in the UK, specific values may be obtained from ONS (Office of National Statistics) datasets, for example qs303ew. |
% > 75 years | over75 | This field requires a numerical input greater than or equal to 0 and less than or equal to 100, representing the percentage of residents older than 75 years. If working in the UK, specific values may be obtained from ONS (Office of National Statistics) datasets, for example qs103ew. |
Additional Grid Data
Flood Hazard (ZUK0). This is output from Flood Modeller 2D simulations. It can be selected in the 2D simulation interface > Domains > Outputs tab. An additional 2dm/dat output will then be generated with flood hazard data. This can then be converted to ASCII grid format using the 2D Flood Map tool or the “2dm_to_ascii.exe” application. Alternatively, the 2D Flood Map tool or the Grid Calculator tool can be used to calculate Flood Hazard as a post-process from the cross product of depth and velocity model outputs (for the same timestep).
Time of Inundation (TExc) – This is the time of the onset of flooding calculated in each model grid cell (measured in hours). The standard 2dm/dat time series output from a Flood Modeller 2D model includes this data. It is added to the waterlevel parameter output as one of the specialised timesteps. It is assigned the “9999.1” timestep. This can be converted to ASCII grid format using the 2D Flood Map tool or the “2dm_to_ascii.exe” application.
Capping and Writeoff of Additional Damages Related to Property Flooding
If a PVD calculation is undertaken applying capping or writeoff settings then damage calculator also applies capping and writeoff to the additional damages related to property flooding.
• Capping to market value – for each property, damage calculator determines the year at which direct property damage equals or exceeds the specified market value. After this point, the property is considered ‘capped’, and no further direct damages are calculated. Furthermore, no additional damages related to property flooding are calculated.
• Write-off at specified AEP – if a property floods more often than the specified writeoff %AEP in a given scenario, it is considered ‘written off’. After this point, no further direct damages are calculated. Furthermore, no additional damages related to property flooding are calculated. It should be noted that this is calculated for upper floor properties, to represent the fact that if the ground floor of a property is written off, the upper floor is also likely to be uninhabitable. If this is not required, the property should be deleted from the property dataset.
• If a property is subject to both capping and writeoff, damage calculator will check for which occurs earliest, and apply that.
Property Level Protection (PLP)
Damage calculator allows the effects on damages of Property Level Protection (PLP) to be calculated. Two datasets are required in the depth-damage data folder to allow PLP calculations to be undertaken. These datasets are detailed in PLP Factor and PLP Measures.
On the Calculation Information tab, tick the box titled 'Calculate damages with property level protection'. A new tab will appear on the Damage Calculator interface titled “Property Level Protection”. This contains details of available sets of adjustment factors (specified in the files described in PLP Measures and RP_DDcurves in both chart and tabular form. The adjustment factors for use can be selected by highlighting in the left-hand list. The Damage Calculator interface plots the revised damage data against the original damage data on the Depth/Damage Curves tab.
The damage analysis should now be ready to start by clicking the run button.
Results are produced in the same format as the standard damage analysis. The output log will contain additional lines to say property level protection was applied in the analysis and references to which property level protection database was used and which curve set within that database was selected.
It should be noted that Damage Calculator uses linear interpolation to calculate the required adjustment factor for depths lying between those specified in the table.
Run damage analysis
The damage analysis should now be ready to start. Two runs buttons are available on the calculation tab – one on the top left in the upper menu bar, another in the bottom right corner.
Damage calculator may display one of the following warning messages:
• ‘The defined appraisal period extends beyond the final epoch (scenario)’. This warning is displayed if the final year of the appraisal period is later in time than the final scenario year. The warning informs the user that the tool will need to extrapolate to calculate PVD unless an additional epoch / scenario is created.
• ‘Additional damages write-off AEP does not match any input grid AEP’. This warning is displayed if the option to write off frequently flooded properties at a specified AEP has been selected and there is no direct match to this AEP in the input flood data. If ‘yes’ is clicked, then the tool will look for the next nearest larger %AEP (i.e. more frequent flooding) dataset and use that to determine if write-off will occur.
The analysis will then start. A progress bar will be displayed in a pop-up window detailing each stage of the analysis. Analysis can take seconds or minutes, depending on the size of the input grids.
On completion of an analysis, the results are displayed in two new tabs (entitled “Results per property” and “Results Summary”).
Saving damage analysis
At any point during an analysis, the calculation (including settings and filepaths of source data) can be saved to an .xml format file. Click the File menu in the upper left corner of the interface and select Save Calculation from the dropdown menu. The File menu can be used to reload calculation files to review or repeat an analysis in a later session.