What custom settings are provided for a Damage Calculator analysis

The Damage Calculator tool enables you to calculate the financial impacts associated to flood depth grids generated by modelling. You may also find the following guide useful: How to calculate property damages from a flood depth grid.

The tool also provides a number of options to customise your analysis. This section provides definitions for these custom options:

Present Value Damages (PVD)

Settings to be specified for PVD calculation are:

1. Appraisal Period – should be set to number of years between earliest and latest specified scenario.

2. Apply capping – tick box to compare calculated PVDs against market value for each property. If PVD for a property exceeds its market value then PVD is capped to market value. By default, the PVD analysis will include capping, so untick the box to not cap.
   Market values for properties can be set up in advance of using Damage Calculator. This is done by adding an extra field to your property dataset (csv text file or shapefile) entitled “MarkVal”. The tool will automatically pick this up and compare the entered value against calculated PVD for the associated property.

Note: Damage Calculator reports which property PVDs are capped in an analysis together with the capped and uncapped PVD values.

3. Interpolation Method – PVD is calculated by interpolating AAD values calculated for each specified scenario to give AAD values for every year of the appraisal period. You need to choose an interpolation method for this calculation, options are:

• Linear – assumes straight lines joining modelled scenario AAD points leading to varying AAD values throughout appraisal period.

• Stepped – assumes constant AAD between modelled AAD points, with a step in distribution occurring at each scenario within appraisal period.

• Combined – assumes a linear distribution between the first and second scenario, followed by a stepped distribution between subsequent scenarios.

Property Level Protection (PLP)

To include property level protection calculation in your analysis you first need to define property level protection datasets (consisting of two csv format text files) and add these to your depth damage data folder. Details on how to define these data are provided in How to setup my Damage Calculator depth damage curve data .

On the Calculation Information tab, tick the box entitled 'Calculate damages with property level protection'. A new tab will appear on the Damage Calculator interface entitled “Property Level Protection”. This contains details of all available sets of adjustment factors in both chart and tabular form. Select the dataset you wish to use in your analysis by highlighting it in the left-hand list.

The Damage Calculator interface enables you to visualise the effect of the selected factors as the revised damage data will be plotted with the original damage data on the Depth/Damage Curves tab and also shown in the adjacent table, as shown below:

When you run your analysis with PLP active, you will get damages and AAD values calculated both with PLP and without PLP. All these results data will be added to the table shown in the Results tab of the interface. When you export your results the PLP data will be included in the all results file and in the summary file (that just presents overall totals for your catchment).

Risk to Life

Damage Calculator has an option to utilise the input depth grid data to also calculate the likely loss of life per property and the subsequent associated cost per input event, AAD per scenario and overall loss of life PVD. All costs are calculated on a per property basis and then summed to produce an overall total. This option is activated by ticking the Calculate Risk to Life box on the Calculation Information tab.

When the option is ticked the calculation of risk to life will automatically be included in your analysis. However, this requires some additional grid inputs. When the Risk to Life box is ticked, two extra columns will appear in the input depth grids table. These are flood hazard rating grid and 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. This procedure must be repeated until every depth grid entry in the table has a flood hazard grid and time of inundation grid specified.

Note that the risk to life analysis is only available if your input flood depth data is also in grid format (and not embedded in the property file as additional attributes).

The additional inputs required for this analysis can be obtained from your Flood Modeller 2D or TUFLOW simulations:

• Flood Hazard – An optional output from Flood Modeller 2D simulations is Flood Hazard. This 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 – 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.

The risk to life calculation will add extra data to the main results table and results summary table. If the input data contains multiple scenarios the likely loss of life (LLOL) per property will be reported as a PVD value (in addition to AAD, per event cost and number of people affected).

The calculation depends on an assumed occupancy per property type, as defined in the Occupancy.csv input data file. This file should be located in your depth damage data folder (a file containing typical UK values is included in the example dataset folder – you have the option to edit this for your analysis).

In addition, the calculation also requires particular attribute fields to be present in your input property dataset. These are the percentage of occupants over 75 and the percentage of occupants who are infirmed. If these data are missing or incorrectly referenced (due to the attributes having unexpected field names) then the risk to life calculations will yield zero loss of life for all properties. Therefore, it is recommended you access the Field Mappings table for your property data to check all required data fields have been correctly picked up.

Custom options on Settings tab

Offset from DEM to Floor Level

For properties with no threshold value defined in your property dataset you can enter a value to be applied as an alternative. This setting will apply globally to all properties that have no specific threshold value. Thus, if a property has a null value entered in its threshold field (note that zero is a valid entry) then the tool will calculate flood depth for the property as (flood depth – Global offset value). You can provide different global offset values for residential and non-residential properties. The default value for both property types is zero (i.e. this setting will have no effect on your analysis if left as the default value).

Include Cellars

Non-residential property types within the MCM datasets (provided by FHRC) are each supplied with two sets of damage curves; one including cellar damages and one excluding these. Tick this option to instruct your damage calculation to use the “with cellar” damage curves. The default option is to use the without cellar curves.

Calculate damages for upper floor levels

This setting (on the Settings tab) is a checkbox, which is unticked by default. If you tick this option then Damage Calculator will use the upper floor code in your specified property dataset (usually property points with this property will be excluded from calculations).

Interpret residential property sub-type codes

Tick this option to instruct Damage Calculator to look for a “HouseType” field in your specified property dataset attributes table. Values read from here will then be used to interpret a more precise MCMcode (and hence associated depth damage curve) for each property analysed, rather than use the residential sector average code (= 1).

Damage Calculator is programmed to recognise “HouseType” entries such as “Det” (= detached), “SDet” (= semi-detached), “Terr” (= terraced) and “Flat” (= flat).

Set alternative property codes

This option allows you to define fixed mappings for selected property codes, this allowing you to customise which depth damage curve a property type (in the property dataset) will use in a damage calculation. For example, you can assign a more precise property type to the miscellaneous type 9.

This option is active by default for all damage calculations (but you can untick to turn it off). This is because Damage Calculator automatically sets up two property code mappings:

• Property code 1 is mapped to the damage curve for code 0 (residential sector average).
• Property code 999 is mapped to the damage curve for code 1000 (non-residential sector average).

This is because the UK national property datasets use these different codes to represent sector averages.
To edit the property code mappings table, the following functions are provided:

• Click on an existing cell and type to edit the entry. Click off the cell to apply the edit.
• Click the Add button, below the table, to add a single, blank row to the table (then type in new values).
• Click on an existing row and then click the Remove button to remove the selected row.
• Click the Save button to write the content of the table to a csv file (you are prompted to provide a filename and location).
• Click the Load button to load property mappings from a previously saved csv file. The loaded data will be appended to the current table (i.e. current entries will not be lost or replaced).
• Right-click on the table to display menu. Select Add Row to add a single, blank row to the table. Select Restore Defaults to reset the table to only contain the two default mappings (described above). All other entries will be deleted.

Treat zero floor areas as valid

Tick this option to prevent Damage Calculator analysis from referring to the default areas data for properties with no floor area defined (in the property dataset).

In some cases, a property might appear more than once in a property dataset, e.g. if the property has multiple uses. To accommodate this, the initial entry for the property might have a non-zero area specified and then for all repeat entries the floor area is set to zero (to prevent double-counting of damages for property). Thus, in these situations, it will be correct to accept the zero area and hence calculate associated damage as zero also.

Customised discount rates

The PVD calculation uses discount rates to transform calculated AAD values for future scenarios back to equivalent present values. Discount rates can vary with time within the appraisal period. Settings tab provides two table of discount rates that the analysis can use. The ‘Standard Rates’ table is applied to direct property damages, vehicle damages, evacuation and accommodation damages and indirect non-residential damages. The ‘Other Rates’ table is applied Emergency Services Costs, Risk to Life and Mental Health Damages. Both tables are pre-populated with values that are the standard rates assumed in UK analyses. (ref. The Green Book 2018: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/685903/The_Green_Book.pdf)

However, you have the option of editing these to create a custom discount rate distribution.

Damage calculator always on top

This setting (on the Settings tab) is a checkbox, which is unticked by default. If you tick this option then the Damage Calculator user interface will always remain on screen in front of other applications (primarily Flood Modeller main interface).

Additional damages related to Property Flooding

In addition to calculating direct damages per property due to flooding, Damage Calculator can also calculate damage values for the following categories of related additional damage:

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.
• Combine with 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, i.e. to be flooded the depth must exceed the sum of vehicle threshold and property 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 additional damages

These additional damages can have capping applied (when calculating PVD). The capping methods are different to that used for property flood damage. Two options are provided:

• Apply capping – for each property the tool determines the year at which property damage equals or exceeds the specified market value. It then sets additional damages to zero from this year onwards and calculates each additional damage PVD based on the sum of PVD contributions up until this year.
• Apply write-off at (or above) specified AEP % - check at which scenario a property experiences flood damage at the specified AEP (default is 33.3%). Write-off will be deemed to occur at this point, so the tool will set additional damages to zero from this year onwards and calculate additional damage PVD based on the sum of PVD contributions up until this year. If the input data has no flood dataset at the specified write-off AEP within a scenario then the next largest AEP is used (e.g. 50%).

You have the option to cap by applying either or both methods (or untick both to apply no capping to additional damages). If both methods are selected (the default option) then for each property, the method that caps the earliest is applied.