Data requirements

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

• Grid Data - used to define water depths to be utilised for damage calculations. Grid datasets must also be provided for inundation times and flood hazard ratings if your analysis is to include a 'Risk to Life' calculation

• Property Data - Used to provide details of property types within the analysis area.

• Depth-Damage Data - Database to define the relationship between damage costs and flood depth for all property types

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:

• Use the 1D Flood Map tool to generate a depth grid from 1D model results (associated to a TIN file) combined with a ground grid (DTM). This tool can extract data from a selected time step or maximum depths and save as an ASCII grid.

• Use the 2D Flood Map tool to extract data for a selected time step or for maximum depths from a 2D results file (in 2dm/dat format). This tool can save these data to ASCII grid format.

• The 2D Flood Map tool may not cope with large 2D results files. For these cases you can 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.

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:

• Time of inundation grid - where grid data values represent time (in hours) for flood water to first inundate each grid cell (the 9999.1 timestep output for the velocity parameter in a 2D simulation).
• Flood hazard rating (HR) grid - where grid data values represent the hazard rating. This can be specified as a direct output from a 2D model or calculated separately as a post process (using velocity and depth datasets).
  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:

• Location (easting / northing)

• Property code – defines type of property (MCM code in the UK)

• Property type – text definition. This is used as a backup to property code, Damage Calculator can recognise selected types of residential property; e.g. “det” = detached, “sdet” = semi-detached.

• Market value – used by present value damage calculation, if user selects option to cap to market value.

• Threshold – used to adjust flood depth, i.e. depth used in calculation = grid depth - threshold

• Floor area – used in conjunction with looked-up damage value per square metre to calculate a total damage for each property

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

• National Property Dataset (NPD)
• National Receptor Dataset (NRD) Property Points Layer

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):

• MCMcode.csv - Lists the possible housing types that may be in your MCM depth damage curve files, with a cross reference to MCM code. Used to lookup which depth damage data curve to use for each property.
• DefaultFloorAreas.csv - Provides a default floor area for each property type (residential and non-residential). This is used with damage per unit area figures to calculate total damage (for properties that do not have a floor area included in their attribute data).
• Occupancy.csv - 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).
• PLPMeasures.csv - 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.
• PLPFactor.csv - Defines adjustment factors to be applied to depth damage data for one or multiple property level protection measures. Note that 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).
• EvacuationCosts.csv - Provided by FHRC as part of MCM (“Mid” values taken from “Evacuation costs – full scale” tables in Chapter 4 of MCM online). The data here provide depth verses evacuation cost relationships for different residential property types (note bungalow property types have no data defined and thus are excluded from evacuation costs calculations – unless you first modify bungalow property types to something different). Evacuation costs vary with depth, however, unlike property damage, costs are not interpolated between the specified depths within each relationship (thus the defined relationships are stepped). Note an example of this file (showing the format, but with made-up values that must be changed before being used in an analysis) is provided by Flood Modeller.

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.