'How to' guides...for Damage Calculator

 

Overview

This is a user guide for the Flood Modeller Damage Calculator tool. The tool is designed to estimate direct property damages (residential and commercial) caused by flooding. In addition it can, at the same time, perform annual averaged damage (AAD), present value damage (PVD), effect of property level protection and risk to life calculations.

The tool takes inputs of series of flood maps (depth grids for different return periods and from different Epochs) and combines these with property datasets (providing property locations and metadata) and depth-damage curves to calculate the damage for each property affected directly by flooding. These data are then summed to obtain total damage figures for each flood event with the option to also calculate AAD and PVD values and to perform risk to life calculations.

The tool has been developed in collaboration with the Flood Hazard Research Centre (FHRC) who are part of Middlesex University London, UK (www.mdx.ac.uk/our-research/centres/flood-hazard). Their research provides property depth damage data for the UK Multi-Coloured Manual (MCM). These data can be downloaded from the website; www.mcm-online.co.uk in a format that can be used directly in Damage Calculator. If you have depth damage data from another source, it can still be used in this tool. However, you will first need to convert your data to the MCM format, which is a series of comma separated text files (.csv). This format is described in the user guide How to setup Damage Calculator depth damage curve data.

The depth damage is used in combination with property data which can be supplied to the tool in either point shapefile or .csv text format. Note that in both formats each property is represented by a single point. Damage Calculator analyses each point to evaluate where it lies within you flood extent depth grid data (e.g. derived from 1D or 2D modelling) and thus what flood depth will be associated to each property for the calculation of damages.

The methods and underlying datasets used follow standard methods as set out in the included References

The guide consists of the following sections:

Contents

How to calculate property damages from a flood depth grid

How to review Damage Calculator results

How to calculate Present Value Damages

How to calculate Annual Average Damages

How to apply Property Level Protection thresholds to damage calculations

How to create a property damage shapefile

How to setup Damage Calculator depth damage curve data

How to create an empty grid to represent the lower limit of flooding

What custom settings are provided for a Damage Calculator analysis?

Risk to life calculations

Data Requirements

References

 

How to calculate property damages from a flood depth grid

 

The Damage Calculator tool can be utilised to calculate property damages for both residential and non-residential properties. These data can be output in spreadsheet or shapefile format. In addition to calculating damages from a single model result, Damage Calculator can also process multiple results from the same Epoch to calculate annualised damage values (AAD) and multiple results from multiple Epochs to also calculate present value damage data (PVD).

This section guides you through the process of using your flood depth grid model outputs to calculate likely damages to affected properties.

Note that this section assumes that you have already acquired a set of depth damage relationships in the required format. The tool has been developed in collaboration with the Flood Hazard Research Centre (FHRC) who are part of Middlesex University London, UK (www.mdx.ac.uk/our-research/centres/flood-hazard). Their research provides property depth damage data for the UK Multi-Coloured Manual (MCM). These data can be downloaded from the website; www.mcm-online.co.uk in a format that can be used directly in Damage Calculator. Alternatively, you can generate your own depth damage data in the same format (for guidance, a sample is provided as part of the Flood Modeller example data). Furthermore, this format is described in the user guide How to setup Damage Calculator depth damage curve data.

To further extend your analysis to include calculation of AAD and PVD or to include customised property level protection within your damage data, see the following sections:

How to calculate Annual Average Damages

How to calculate Present Value Damages

How to apply Property Level Protection thresholds to damage calculations

To calculate damages for a single depth grid output from a flood model:

  1. Add an ASCII format grid of flood depth data to your current project. This may be a grid already created, in which case load in the Layers Panel using Add GIS data. Alternatively, this may be created by post-processing either 1D or 2D model results, using the relevant flood map calculator tool on the Results tab of the main Toolbar (See How to use the 1D Flood Calculator; How to use the 2D Flood Calculator for details.)

  2. You will need a point shapefile or csv format text file that represents your property data. This can be added to your project if it is a shapefile (also csv files can be imported as new shapefiles), however it is not essential as you will have the option to browse to this file later in the process.

  3. Two main sources of property data available for use in flood and coastal erosion risk management in England and Wales are:

  4. Start the Damage Calculator tool from the Toolbox > Post Processing Tools section. You will be prompted to automatically preload any depth grids you want to use to calculate damages and also your property dataset. Select the depth grid you are analysing and your property dataset shapefile (if it is present in the Layers panel of your project).

  5. After making any selections, click OK to proceed and the Damage Calculator tool will open in a new window (in front of Flood Modeller) after a few seconds. Any files selected in the previous window will be added in the appropriate locations within the interface.

  6. Note that the property data file you specify needs to include particular attributes to enable the damage calculator to look-up the appropriate damage data associated to each property type. You can click the Field Mappings button to check the attribute fields in your specified file and also check how Damage Calculator has assumed these fields “map” to the required fields for the analysis. These field mappings are displayed in a pop-up window and this also allows you to modify the mappings and save these revised settings for your analysis.

    Note: If you are running this tool for the first time it is likely it won’t have a location stored for your depth damage curves data. In this case the tool will prompt you to specify a folder which should contain ONLY the required data files defining depth damage relationships for different property types plus some associated data. The required files should have the following names and content:

    Details on the format of the content of each of the above data files are provided in the section: How to setup Damage Calculator depth damage curve data

  7. Specify an output folder where you wish your damage calculator results to be written. Results are generated in a series of csv format text files (that can be loaded directly into MS Excel), together with a “.log” text file that is generated as a log of your analysis. The log file provides a record of the associated metadata, e.g. input grids, analysis settings, plus any issues arising during the analysis, e.g. a list of properties with no type defined. The output folder can be typed or pasted into the available space. Alternatively, a button is provided enabling you to browse to a folder.

  8. If you have not pre-selected a property shapefile (from your main Flood Modeller interface) then you need to use the adjacent browse button to specify either a shapefile or csv format file.

  9. Select your depth damage data source. Depth damage data are provided in CSV format – supplied by Flood Hazard Research Centre (FHRC) in the UK. All depth damage files should be placed in the same folder and it is this folder that must be referenced within the Damage Calculator tool. The folder is referenced in the tool interface on the Settings tab. A button is provided to browse to this folder (see below).

  10. Guidance on how to define new or edit existing depth damage csv data files is available here: How to setup Damage Calculator depth damage curve data

    Depth damage data files should contain data from a single year. The tool will read the year field for the first row of data and report this in the interface.

  11. A set of MCM csv files will include multiple depth damage data curve sets. Each set will represent the combined effect of particular attributes of flooding. These are:

  12. Furthermore, each curve set provides depth/damage relationships for a range of different property types. These might be residential only, non-residential only or a combination of residential and non-residential.

    To select a curve set, go to the Depth/Damage Curves tab of the interface. This provides descriptions of the available variations within the selected data folder (the tool extracts these from the datafiles) and enables you to select a separate curve set for residential and non-residential properties, via two dropdown lists (as shown in the screenshot below). Note, the available variations are different for residential and non-residential property types.

    Your selected curve sets for both residential and non-residential properties are listed in the left-hand panel (in a tree view). You can expand any branch to drill down and access available sub-types for each of the main property types listed. The underlying depth/damage data associated to the selected (highlighted) row is plotted on the adjacent chart and listed in the adjacent table, as shown in the example below:

  13. There are additional custom settings that can optionally be specified for your damage analysis. These are:

  14. More details on these custom settings are available here: What custom settings are provided for a Damage Calculator analysis?
  15. Your damage analysis should now be ready to start. Go to the Calculation Information tab and click the Run button. The analysis will start and a progress bar will be displayed in a pop-up window detailing each stage of the analysis (i.e. reading inputs, calculating damages, etc.). Analysis can take seconds or minutes (depending on the size of the input grids).

  16. On completion of an analysis, the results are displayed in a new tab (entitled “Results”). The results table combines the key attributes of each property identified within the flood extent with the calculated depth and associated damage. The total damage is also displayed below the relevant column in the table. If multiple grids are included in the analysis then the results table will contain multiple depth and damage data in extra columns, together with an AAD value.

    The analysis writes the tabular results data to a series of csv format text files. One contains all data displayed on the Results tab and the other contains just overall total damages for each input dataset (plus separate totals for residential and non-residential properties). These data can be reviewed in Excel by clicking the View Summaries button on the Results tab. Note that, if a PVD calculation is performed, an additional csv file is generated that provides a check of the contributions to PVD for each year of the specified appraisal period.

    Clicking the Export to Shapefile button will generate a new point shapefile with each point corresponding to a row in the currently displayed data, with the displayed tabular data included as feature attributes. These data can also be automatically added to your Flood Modeller map view by ticking the View in Flood Modeller checkbox prior to exporting.

    The export buttons are located below the table on the Results tab.

  17. If you right-click on any header within the results table you can access tools to customise the displayed data. The available tools are as follows:

  18. Each damage analysis performed generates a log file in your specified output folder. The contents of this can also be viewed in the Damage Calculator interface on the Output log tab. This log file will include a summary of your analysis settings and any notes describing the simulation (added in the Project Notes section of the interface). In addition, any issues during the analysis are listed, e.g. where a property’s (MCM) code did match any of the curves included in the nominated depth damage database.

  19. After completing your analysis, you can save the settings you specified to an xml format settings file, referred to as a Damage Calculator calculation file. Click the File menu in the upper left corner of the interface and select Save Calculation from the dropdown menu.

  20. Use the File menu to then reload a calculation file to review or repeat your analysis in a later session. Note that many of the default Damage Calculator settings (e.g. nominated depth damage data folder) will be stored by the tool and be present by default at the start of your next session.


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How to review Damage Calculator results

 

On completion of a Damage Calculator analysis, results are displayed in a new tab entitled results. The following steps detail how to review these results.

  1. The results table combines the key attributes of each property identified within the flood extent with the calculated depth and associated damage. The total damage is also displayed below the relevant column in the table. If multiple grids are included in the analysis then the results table will contain multiple depth and damage data in extra columns, together with an AAD value.

    The analysis writes the tabular results data to a series of csv format text files. One contains all data displayed on the Results tab and the other contains just overall total damages for each input dataset (plus separate totals for residential and non-residential properties). These data can be reviewed in Excel by clicking the View Summaries button on the Results tab. Note that, if a PVD calculation is performed, an additional csv file is generated that provides a check of the contributions to PVD for each year of the specified appraisal period.

    Clicking the Export to Shapefile button will generate a new point shapefile with each point corresponding to a row in the currently displayed data, with the displayed tabular data included as feature attributes. These data can also be automatically added to your Flood Modeller map view by ticking the View in Flood Modeller checkbox prior to exporting.

    The export buttons are located below the table on the Results tab.

  2. If you right-click on any header within the results table you can access tools to customise the displayed data. The available tools are as follows:

  3. Each damage analysis performed generates a log file in your specified output folder. The contents of this can also be viewed in the Damage Calculator interface on the Output log tab. This log file will include a summary of your analysis settings and any notes describing the simulation (added in the Project Notes section of the interface). In addition, any issues during the analysis are listed, e.g. where a property’s (MCM) code did match any of the curves included in the nominated depth damage database.

  4. After completing your analysis, you can save the settings you specified to an xml format settings file, referred to as a Damage Calculator calculation file. Click the File menu in the upper left corner of the interface and select Save Calculation from the dropdown menu.

  5. Use the File menu to then reload a calculation file to review or repeat your analysis in a later session. Note that many of the default Damage Calculator settings (e.g. nominated depth damage data folder) will be stored by the tool and be present by default at the start of your next session.


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How to calculate Present Value Damages

 

The Damage Calculator tool can interpolate damages from multiple simulation results from multiple Epochs to determine present value damage (PVD) figures (for each property and an overall total). Furthermore, these data can be compared to user specified market values and capped if PVD exceeds these values, thus producing capped total PVD figures.

PVD data are calculated by combining the calculated annual average damage (AAD) values for a series of Epochs, e.g. current year plus one or more future climate scenarios within a user specified appraisal period. For each year within the appraisal period additional AAD values are interpolated – multiple interpolation methods are available (stepped, linear and a combination of these two). Each AAD value is then discounted back to a present-day value using user specified discount rates (which can vary across the specified appraisal period). All yearly values are then summed to calculate the overall PVD value. The user then can choose to cap this value to a user specified market value (which can be set by property type or on a per property basis). It should be noted that the user should select Epochs for their initial flood modelling produces AAD values at the key points within the appraisal period to enable the selected distribution to be defined, e.g. at step points for a stepped interpolation. Damage Calculator can help reduce the number of flood depth grids required for this analysis as it allows the same grid to be re-used in multiple Epochs (representing a different return period in each, e.g. 100yr RP grid in 2017 might be used as the 10yr RP grid in 2050).

See the section entitled How to calculate property damages from a flood depth grid for details on the general operation of the Damage Calculator tool. This section describes the full PVD calculation process, however it only provides details for the additional procedures related specifically to PVD calculation:

  1. PVD calculation requires AAD data from multiple Epochs. To calculate AAD for an Epoch, you will need to have flood depth grids (in ASCII format – with extension “.asc”) calculated from multiple simulations (i.e. minimum of 2) each representing a different flood return period scenario for your model extent. If you have these loaded in your Flood Modeller project they can be automatically loaded into the Damage Calculator tool when you access it from the Flood Modeller toolbox (Post-processing tools section). In addition, you can also specify a property data file to be pre-loaded if it is in point shapefile format and you have it loaded in your Flood Modeller project.

  2. To generate results for all Epochs might require a significant number of simulations. This number can be reduced if you can re-use flood grids in multiple Epochs, e.g. a 100yr return period result in 2018 Epoch could be used to represent 20yr return period in 2068 Epoch. Flood Modeller provides tools to create copies of grids, e.g. Grid Calculator using the expression “original grid x 1” would achieve this. However, Damage Calculator includes functionality that enables you to use the same grid multiple times, i.e. no need to copy.

  3. After loading the depth grids created by your modelling, highlight a row and click the adjacent Copy button. The selected row(s) will be repeated in the table, but with the Epoch and RP fields left blank. These fields must then be filled in by clicking on a field and typing a value (note both fields must have integer entries).

  4. Once you have data from multiple Epochs loaded in the Depth Grids table the PVD calculation options will be available. Tick the Calculate PVD checkbox and the associated PVD settings will be enabled.

  5. Settings to be specified for PVD calculation are:

  6. After reviewing all PVD settings you can proceed with your damage analysis as normal, i.e. click Run on the Calculation Information tab.

  7. Note: You can also save the analysis you’ve defined, together with all settings, to a Calculation file (xml format text file). Click File > Save Calculation and provide a suitable filename and location. This will enable you to repeat the analysis in a future session if required.

  8. When the calculation has completed the inclusion of PVD analysis will lead to some additional outputs:


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How to calculate Annual Average Damages

 

The Damage Calculator tool can interpolate damages from multiple simulation results to determine an annual average damage (AAD) figure (for each property and an overall total).

See the section entitled How to calculate property damages from a flood depth grid for details on the general operation of the Damage Calculator tool. This section describes only the additional procedures required to incorporate annual average damage (AAD) outputs into your analysis.

  1. To calculate AAD you will need to have flood depth grids (in ASCII format – with extension “.asc”) calculated from multiple simulations each representing a different flood return period scenario for your model extent. If you have these loaded in your Flood Modeller project they can be automatically loaded into the Damage Calculator tool when you access it from the Flood Modeller toolbox (Post-processing tools section). In addition, you can also specify a property data file to be pre-loaded if it is in point shapefile format and you have it loaded in your Flood Modeller project.

  2. The Damage Calculator tool looks at each grid filename and attempts to evaluate the associated return period for each depth grid. These values are used to calculate the AAD values so it is recommended you check the RP column in the Events table and amend values that the tool has got wrong.

  3. The specification of your damage analysis is done in the same way as described in How to calculate Property Damages from a flood depth grid.

  4. After specifying the analysis, it can then be run. Note that the simulation will take a little longer to complete as you have multiple grids specified. You will see the progress bar pop-up window work through reading each specified grid concurrently.

  5. The results table obtained from this analysis will contain additional columns compared to a basic single grid run as the depths and associated damages incurred due to each specified flood extent will be listed in separate columns. Furthermore, the results with AAD ticked on will include an additional column that displays the AAD values for each property identified within the flood extent. In addition, the total ADD for the analysis will be provided at the foot of the results table, under the AAD column.

  6. AAD values will also be exported to the summary csv files and if you export to a new point shapefile, automatically loaded into the Flood Modeller map view.

  7. After loading the damage data shapefile in Flood Modeller you can modify the settings to highlight the largest AAD values. This enables you to check for any anomalies at these key locations and thus verify your model results.

  8. The standard display when a point shapefile is loaded into the map view is shown below. Each feature (point) in the shapefile is displayed with the same size and colour.

    Right-click on the shapefile in the Layers panel to display the layer properties (in a new window). Select the Symbology tab and Visual Style sub-tab as shown below:

    The display in the map view will now clearly show the locations of properties with maximum AAD values. Use the map tools (i.e. zoom, pan and info tool) to investigate the causes of these high values further.


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How to apply Property Level Protection thresholds to damage calculations

 

The Damage Calculator tool calculates damages per property for one or multiple flood extents. Properties are specified by a point shapefile (or csv format text file) and the flood extents are defined as ASCII format depth grids. The tool also includes an option to apply user specified property level protection, e.g. individual property flood gates providing resistance to flood waters. This will modify the depth damage curves used to calculate property damages to reduce the impact of flooding up to a specified threshold, at which point the damage curve reverts to its original values.

This section describes how to apply property level protection to your depth damage calculations:

  1. Open the Damage Calculator tool, load your flood depth grids and property datasets and specify your damage analysis as normal. This process is described in this guide in the section entitled How to calculate property damages from a flood depth grid.

  2. Define a property level protection dataset. This consists of two csv format text files that once created need to be placed in the same folder as your depth damage data to enable Damage Calculator to recognise them. One text file describes depth verses damage reduction factor relationships for one or multiple property level protection options. The other text file provides a name for each property level protection option you define and a cross reference ID to relate to the associated data in the data series file.

  3. An example pair of property level protection csv files are included within the example damage data zip file packaged with Flood Modeller.

    You can use the example files as a start point and then either add new depth varying data series or edit the existing values. Note that Damage Calculator will use linear interpolation to calculate the required adjustment factor for depths lying between those specified in the table.

    The data files used in your analysis must have the names; PLPMeasures.csv and PLPFactor.csv. The format of each file is as follows:

    PLPMeasures.csv

    An example of this dataset is provided by Flood Modeller. This file defines one or multiple property level protection measures. The description of the measure is listed here and the associated adjustment factors (in the PLPfactors file) are referenced. If you have these data in your data folder you have the option of calculating the effect of property level protection on damages.

    Required columns are:

    PLPFactor.csv

    An example of this dataset provided by Flood Modeller. This file defines adjustment factors to be applied to depth damage data for one or multiple property level protection measures. The same factors will be applied to all property types if you choose to analyse the effect on damages of a particular property protection measure (if you have these data in your data folder).

    Required columns are:

  4. On the Settings tab of the Damage Calculator tool you will have already set the path to your depth damage data folder. Therefore, once you have specified your property level protection csv files and added them to this folder, the tool should be able to just pick them up and use them. Note: You may have to close Damage Calculator and then restart it for it to refresh and recognise your property level protection data. This is signified by the property level protection checkbox on the Calculation Information tab becoming enabled (so you can tick it).

  5. 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.

  6. 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:

  7. Your damage analysis should now be ready to start. Go to the Calculation Information tab and click the Run button.

  8. Results are produced in the same format as the standard damage analysis, i.e. in tabular form on a new “Results” tab that appears once analysis has completed. However, the table contains extra columns as damages are calculated both with and without property level protection applied. Furthermore, 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.


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How to create a property damage shapefile

 

The following steps detail how to create a property damage shapefile.

  1. You will need a point shapefile or csv format text file that represents your property data. This can be added to your project if it is a shapefile (also csv files can be imported as new shapefiles), however it is not essential as you will have the option to browse to this file later in the process.

  2. Two main sources of property data available for use in flood and coastal erosion risk management in England and Wales are:

  3. If you have not pre-selected a property shapefile (from your main Flood Modeller interface) then you need to use the adjacent browse button to specify either a shapefile or csv format file.

  4. Select your depth damage data source. This is the database defining the depth damage relationship for each property type.

  5. Guidance on how to define new depth damage datasets is available here: How to setup Damage Calculator depth damage curve data.

    Note also that the selected data will represent particular attributes of flooding. These are:

    The database is selected on the settings tab of the Damage Calculator interface. A button is provided to browse to your damage database.


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How to setup Damage Calculator depth damage curve data

 

Damage Calculator has been developed in collaboration with the Flood Hazard Research Centre (FHRC), who are part of Middlesex University London, UK (www.mdx.ac.uk/our-research/centres/flood-hazard). Their research provides property depth damage data for the UK Multi-Coloured Manual (MCM), These data can be downloaded from the website; www.mcm-online.co.uk in a format that can be used directly in Damage Calculator.

The Damage Calculator tool must be associated to a set of depth damage curve data in order to perform any analyses. These data are a combination of data files provided by UK Flood Hazard Research Centre (FHRC) as part of the Multi-Coloured Manual (MCM) and a series of additional files provided as part of Flood Modeller. All data are text files with a comma separated (csv) format, which enables you to view or edit (in a text editor or MS Excel). Your data files should be set up in a single folder, ideally with no additional files or sub-folders present in the folder (although Damage Calculator may still be able to read the data even when extra files are present).

This section explains the content and format of each required and optional data file. This will enable you to define new data files if desired or view/edit existing files.

Damage Calculator expects each file specified here to have the column headers specified EXACTLY as specified here. The tool will not accept datasets with incorrectly defined column headers, missing columns or extra columns. If the tool encounters an invalid file it should report the fact (and then abort starting up).

MCM Depth Damage Curve Scenario.csv

This file is provided by Flood Hazard Research (FHRC). Dataset is part of the UK Multi-Coloured Manual (MCM). This file lists the scenarios for which depth damage data are provided, e.g. Short_NoW_storm, which represents a short duration storm event (<12hrs) with no warning. Other options to include in scenarios are contaminated water, saline water, wave impacts or sewerage. Note and example of this file (with just two property types included) is provided by Flood Modeller.

Required columns are:

The columns representing properties of flooding are used together with the curve name field in the Damage Calculator interface to help you select the appropriate data for your analysis. They appear in the dropdown lists of available depth damage datasets to provide complete descriptions of each dataset, as shown below:

In addition, the version of the data files is displayed in the interface (on the Settings tab).

The curve IDs are used within the analysis process to look up the associated depth damage values within the other files within the data folder (see below for descriptions of these).

RP_DD_curves.csv

This file is provided by FHRC as part of MCM. This file lists the depth damage relationships for different types of residential properties. Curves are provided for some or all defined storm scenarios. Note an example of this file (with just two property types included) is provided by Flood Modeller.

Required columns are:

NRP_DD_curves.csv

This file is provided by FHRC as part of MCM. This file lists the depth damage relationships for different types of non-residential properties. Curves are provided for some or all defined storm scenarios. Note an example of this file (with just two property types included) is provided by Flood Modeller.

Required columns are:

MCMCode.csv

This file is provided by Flood Modeller (in a DamageCalculatorData zip file, included in the GUI installation folder). This file lists the possible housing types that may be in your MCM depth damage curve files, with a cross reference to MCM code.

Required columns are:

Both of these data will be displayed in the Damage Calculator tool on the Depth/Damage Curves tab, enabling you to select a property type (for a user selected residential or non-residential curve set) and review the associated depth damage data (in the adjacent chart and table):

DefaultFloorArea.csv

A file is provided by Flood Modeller (in a DamageCalculatorData zip file, included in the GUI installation folder). This file provides a default floor area for each property type (residential and non-residential). These data can be used to calculate damages for properties with no floor area specified in the property file. Note using this file is an option, alternatively you can opt to consider zero damage for properties with no floor area specified.

Required columns are:

Occupancy.csv

File is provided by Flood Modeller (in a DamageCalculatorData zip file, included in the GUI installation folder). This file provides average occupancy figures for each property type. These data are utilised in the optional risk to life calculation within Damage Calculator (note this option also requires additional input data to be prepared, i.e. flood inundation data and flood hazard data).

Required columns are:

PLPMeasures.csv

An example of this dataset is provided by Flood Modeller. This file defines one or multiple property level protection measures. The description of the measure is listed here and the associated adjustment factors (in the PLPfactors file) are referenced. If you have these data in your data folder you have the option of calculating the effect of property level protection on damages.

Required columns are:

PLPFactor.csv

An example of this dataset provided by Flood Modeller. This file defines adjustment factors to be applied to depth damage data for one or multiple property level protection measures. The same factors will be applied to all property types if you choose to analyse the effect on damages of a particular property protection measure (if you have these data in your data folder).

Required columns are:

If you are running Damage Calculator for the first time it is likely it won’t have a location stored for your depth damage curves data. In this case the tool will prompt you to specify a folder which should contain ONLY the required data files defining depth damage relationships for different property types plus some associated data.


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How to create an empty grid to represent the lower limit of flooding

 

Damage Calculator can calculate Annualised Average Damage (AAD) values. The required input data for this analysis are flood model results from multiple simulations representing different return period scenarios (within the same Epoch). The AAD calculation process will plot these data on a chart of damage verses probability (i.e. return period). It will then calculate the area under this chart as the AAD value.

The calculation assumes a linear extrapolation of the chart from the highest return period dataset to obtain the zero-probability damage value. This enables the calculation of the additional area contributing to AAD beyond the highest return period, as shown in the diagram below:

As the above diagram shows, the AAD calculation does not consider any contribution to AAD total from low level flooding (i.e. low damages from return periods smaller than lowest modelled RP).

Depending on your available model data, this omission is likely to have a negligible effect on total AAD. However, if you wish to include a contribution from this area you will need to make an assumption for the highest return period that leads to zero damage (i.e. the onset of flooding or flood damage). You will then need to define a dummy grid consisting of all missing data entries (i.e. “-9999”) that, when added to your Damage Calculator analysis, will result in zero damage and when assigned your onset of flooding return period will provide the AAD calculation with the required data to include the “initial triangle” area (on the above damage curve).

This section explains how to set up a dummy grid to represent zero damage for your study area:

  1. Load the flood depth grids that your modelling has already produced into the Flood Modeller map view (using Add GIS Data button).

  2. On the Map Tools tab of the main toolbar, click on the Grid icon to reveal a sub-menu of grid related tools. Select the Grid Calculator tool.

  3. The Grid Calculator will be displayed in a new pop-up window. It allows you to build a mathematical expression that includes one (or more) of the compatible grids currently loaded in the map view. When the Grid Calculator starts up, your currently loaded grids are listed on the left side. The expression you will build to create a zero-damage grid can use any of your existing flood depth grids, assuming they are all the same in terms of resolution, numbers of rows and columns and lower left coordinate (which they likely will be if they are all derived from different scenarios run using the same model). The selected grid will be used only to define the size and location of the grid, while the expression will define the cell values (setting all to the missing data flag = “-9999”).

  4. Start the expression definition with an open bracket - click the appropriate button to add bracket symbol in expression textbox (at top of window). Then highlight one flood depth grid in the left-hand list and click “Add Layer to Expression”. The selected grid should appear in the Expression textbox.

  5. Build an expression to set all existing grid values to zero and then subtract 9999 to set all cell values to “-9999”. This expression will be:

  6. Click on the calculator keypad to build the expression. The final version should look like this:

  7. Use the browse button (next to the Output file textbox) to specify a filename and location for the new grid the tool will produce. Ensure the Load to View checkbox is ticked and then click Run.

  8. The new grid will be added to your current project, however it will initially not be visible in the map. This is because Flood Modeller by default will not show cells set to the missing data value. You should see the new grid added to the top of the Layers Panel. To check it has been created correctly:

    1. Double-click on the new layer in the Layers Panel (or select Properties in the right-click menu). The Properties window will be displayed.

    2. Go to the Symbology tab and select the Colour Ramp sub-tab

    3. Below the colour ramp tick the Visible checkbox for “NoData” values

    4. Click OK. The new grid should appear as a solid rectangle, coloured to whatever the Displayed Colour setting was set to for NoData (this is black by default)

  9. You can now add this grid to your Damage Calculator analysis with the associated return period set to whatever you want to represent the onset of flood damages. This will ensure the low return period, low level damages are included in your calculation of AAD.


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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. Other sections in this user guide detail How to use this using default settings tool.

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:

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 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. 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.

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

The risk to life calculation will add an extra column to the main results table. This shows the likely loss of life (LLOL) per property.

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 then the risk to life calculations will yield zero loss of life for all properties.

Include Cellars

Non-residential property types within the MCM datasets (provided by FHR) 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:

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:

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 Epochs back to equivalent present values. Discount rates can vary with time within the appraisal period. The Settings tab provides a table of discount rates that the analysis will use. This is pre-populated with values that are the standard rates assumed in UK analyses. 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).


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Risk to life calculation

The risk to life calculation uses the methods defined in the following key references (it is recommended you refer to these references to understand the method):

  1. Defra flood and coastal defence appraisal guidance - social appraisal - supplementary note to operating authorities - Assessing and valuing the risk to life from flooding for use in appraisal of risk management measures, May 2008. (Referenced below as: Defra 2008)

  2. Defra research contract: reservoir safety advice - supplement no. 1 to interim guide to quantitative risk assessment for UK reservoirs, May 2006 (Referenced below as: Defra 2006)

Input Data (ASCII grids)

Flood hazard rating (HR)

Flood hazard rating (HR) is calculated using the following equation (from Defra 2008).:

HR = d x (v + 0.5) + DF

Where:

d = depth of flooding (m)

v = velocity of floodwaters (m/s)

DF = debris factor

The debris factor varies as follows:

DF = 0 if depth ≤ 0.25m

DF = 1 if depth > 0.25m or if velocity > 2m/s

These data can be output directly from the 2D Solver (select additional output option on Domains > Outputs tab of 2D model interface).

Damage Calculator requires flood hazard data to be defined in ASCII grid format (.asc). Multiple options are available to generate these data:

Time of inundation

Time of inundation for each cell in a 2D model is the time (in hours) when the cell first becomes wet (this is used to determine the Speed of Onset score). This parameter is calculated by the 2D Solver and written to the 9999.1 timestep of the velocity parameter output. However, Damage Calculator requires these data to be defined in ASCII grid format (.asc). Thus, you will need to use the 2D Flood Map tool in Flood Modeller to extract this timestep from the 2D results file as a new ASCII grid. For larger file sizes you may need to utilise the “2dm_to_ascii.exe” program. This is located in the “C:\Program Files\Flood Modeller\gui” folder and is run from the Command Prompt window).

Input Data (Property Attributes)

Property data

Risk to life calculations are undertaken based on property details. For each property the following data are required:

Calculations (using steps from Defra 2008)

  1. Calculate flood hazard: HR. The 2D Solver can directly calculate these values.

  2. Calculate area vulnerability (AV): Defra 2008 defines this as the sum of scores for: flood warning, speed of onset and nature of area.  In general, each score has a minimum of 1 and a maximum of 3 and hence the AV is in the range 3 to 9. The Damage Calculator calculates the AV as the sum of these scores.

  3. The 'speed of onset' score is calculated in Damage Calculator using the following algorithm:

    Nature of Area and Flood Warning Score is provided by user as part of the property dataset.

  4. Calculate those exposed to the flood: The first part of this calculation is to estimate the number of people likely to be located in the flooded area.

    The method uses the Defra 2006 method which was specifically derived from estimating the average number of people likely to be present in inundation areas following a reservoir dam break

    For residential properties (MCM codes starting with a “1” or residential property sector average = 0), a national average household size of 2.3 is used (from Defra 2006) together with an assumed occupancy factor of 50%. Thus, each residential property is given a likely population present value, N(Z), of 1.15.

    For non-residential properties (MCMcodes other than 1), the occupancy estimates are taken from Defra 2006. For farm buildings (MCM code 810) the occupancy value is 1 per building with an occupancy factor of 30%. For other non-residential properties, the values are a function of floor area as shown in the table below. Thus, if the floor area for a retail property (MCM code 21) is 100m², then the estimated occupancy is 3.33, which together with an occupancy factor of 30%, gives an average number of people within the building of 1.

    The occupancy data are held in a file called “Occupancy.csv” which must exist in your specified depth damage data folder. The version of this file supplied in the example depth damage folder (in the Flood Modeller example data zip file) contains the data shown in the table below. If the MCM Code for a property does not exist in the occupancy lookup file (or if the MCM Code field for the property is blank) then the associated property will be excluded from the analysis. A comment will be added to the analysis log file that states “Warning: Occupancy not matched ” plus the associated property MCM code (you could then use this information to edit the “Occupancy.csv” and re-run).

     
  5. strMCMCode

    blnPerBuilding

    dblOccupancyRate

    dblOccupancyFactor

    1

    TRUE

    2.3

    50

    2

    FALSE

    40

    25

    21

    FALSE

    30

    30

    214

    FALSE

    160

    21

    22

    FALSE

    160

    21

    23

    FALSE

    40

    21

    234

    FALSE

    10

    15

    235

    FALSE

    8

    10

    3

    FALSE

    40

    21

    4

    FALSE

    40

    25

    410

    FALSE

    200

    30

    5

    FALSE

    40

    25

    511

    FALSE

    100

    50

    6

    FALSE

    40

    25

    610

    FALSE

    7

    20

    630

    FALSE

    5

    5

    8

    FALSE

    60

    21

    810

    TRUE

    1

    30

    9

    FALSE

    40

    25

     

    Defra 2008 calculates X, the % of people exposed to risk, as the product of HR and AV and caps this to a maximum of 100%. The same calculation in Damage Calculator is capped to 100%.

  6. The number of people exposed, N(ZE): Defined as the product of X and the average number of people likely to be present at the receptor (Pop), ie:

  7. N(ZE) = (HR x AV) x Pop

  8. Calculate people vulnerability (PV): Defra 2008 defines PV as the sum of the % > 75yrs and the % infirm.

  9. Calculate number of possible fatalities: Defra 2008 defines this as:

    N(ZE) x {2 x PV x 2 x HR}

    where the value in brackets is expressed as a percent according to Defra 2008.

    Within the Damage Calculator software this is implemented as:

    LLOL (likely loss of life) = (min[(HR x AV), 100] x Pop) x 2 x (%infirm + %>75yrs) x 2 x HR/1,000,000

    The division by 1,000,000 is made up of 1/100 for converting the HRxAV percent value to a decimal, 1/100 for converting the (%infirm + %>75yrs) from a percent to a decimal, and a further 1/100 for converting the {2 x PV x 2 x HR] value from a percent to a decimal.

Example of calculations

As an example of the calculations, the data contained in Annex 1 of the Defra 2008 Note have been run through the Damage Calculator. The table below contains the values from the Defra Note compared with those calculated using the Damage Calculator. The values from the Damage Calculator are consistent with the values from Defra 2008 (which are rounded to show no decimal places).

 


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Data Requirements

Damage Calculator requires the following input datasets in order to define an analysis run:

Damage Calculator will then use these data to ascertain flood depths at each property location. These data will then be combined with the associated damage curve data to calculate individual property damages and hence overall damages in your analysis area.

Grid Data

Grid datasets are used to define water depths or water levels to be utilised for damage calculations. Grid format datasets must also be provided for inundation times and flood hazard ratings if your analysis is to include a 'Risk to Life' calculation. Damage Calculator will intersect these data with your specified property dataset to determine grid cell values underlying each property location.

Grids must be in ASCII format, with file extension “.asc”. Flood Modeller provides tools for post-processing your 1D and 2D model results to generate these grid data. Options are:

Note: If water levels are specified in your input grids, then you will need an associated threshold level defined for each property in your property dataset. This is to enable calculation of flood depths, i.e. water level - threshold.

In addition to grids defining flood depths, your analysis can also be specified with further grids to include risk to life calculations. The required data in these grids are:

These datasets are explained further in the Risk to Life section.

Property Data

A property dataset in either point shapefile or csv text file format is required to provide details of property locations within the analysis area. The property dataset needs to include various metadata which is used by the damage calculation process. A selection of key attributes are:

Two main sources of property data available for use in flood and coastal erosion risk management in England and Wales are:

Depth-Damage Data

A series of csv files are used to define the relationship between damage costs and flood depth for all property types.

Damage Calculator will ascertain flood depths at each property location and then look up the associated damage for the given property type and for the selected curve set. Individual property damages are then combined to calculate overall damages in your analysis area.

Multiple curve sets can be defined in a set of depth damage data files. These can represent things like different levels of flood warning or flood duration or whether property damage includes or excludes cellar damage. There can also be curve sets that relate to particular water types, e.g. saline or contaminated. You can select individual curve sets for your residential and non-residential properties within your damage calculation.

The depth damage data files must be defined in a common folder which is then specified in your damage calculator settings. In addition to the depth damage curves, this data folder must also contain the following extra files (all in csv text file format):

Note all these files must exist in the folder and use the exact filenames specified above. The data files downloaded from MCM online (www.mcm-online.co.uk) must use the filenames as specified on the website (i.e. “RP_DD_curves.csv” and “NRP_DD_curves.csv”).

The format of these data are explained in the section entitled How to setup Damage Calculator depth damage curve data. Furthermore, see below for information on the example damage data supplied with Flood Modeller.

Example Data

An example set of data are included within the Flood Modeller example data files. The example data is held in a zip file in the installation folder (usually “C:\Program Files\Flood Modeller\gui”). You can copy this elsewhere and manually unzip or use the unzip option located on the Start tab of the main toolbar in Flood Modeller.

Also included in the example data are a complete set of depth damage data files (in csv format). These define damages for a single residential and single non-residential property for a single flood type – to demonstrate the required format for these data.

The example data folder also includes (csv text) files defining MCM code, floor areas, occupancy rates and property level protection factors. These files can be reused (edited if required) in new depth damage data folders you may set up with full versions of the depth damage curves provided by MCM online (www.mcm-online.co.uk) or manually defined (using formats described in How to setup Damage Calculator depth damage curve data).

 


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References

Penning-Rowsell, E., Johnson, C., Tunstall, S., Tapsell, S., Morris, J., Chatterton, J., and Green, C. 2005. The benefits of flood and coastal risk management. A handbook of assessment techniques. (The Multi-Coloured Manual). Flood Hazard Research Centre, Middlesex University.

Brown, A.J. and Gosden, J. D., 2004. Interim Guide to Quantitative Risk Assessment for UK Reservoirs. Thomas Telford.

Defra, 2006. Supplement No 1 to Interim Guide to Quantitative Risk assessment for UK Reservoirs. Draft to accompany public consultation on Draft of Guide to Emergency Planning. Rev 01. May 2006.

Defra, 2008.  Defra flood and coastal defence appraisal guidance - social appraisal - supplementary note to operating authorities - Assessing and valuing the risk to life from flooding for use in appraisal of risk management measures. May 2008.