Flood data

Specify depth information

Flood depth information for a range of scenarios (future years with varying climate change or defence scenarios) and probabilities (in return period or %AEP format) must be input to the ‘depth grids’ section at the bottom of the ‘calculation information’ tab.

Flood depth grids must be in ESRI ascii format, as defined here: https://www.loc.gov/preservation/digital/formats/fdd/fdd000421.shtml.

Flood Data

Flood Data may be input to damage calculator in one of two ways – as water depth / level grids, or as attributes in the property dataset. Damage calculator provides two options for input of flood depth / level data. This can be input either via hydraulic model results (as water depth or water level grids), or via columns in the property dataset.

Both methods (water depth / level grids) are described below:

Flood Data in Depth Grids / Level Grids

Grid datasets are used to define water depths or water levels used for damage calculations. If a ‘risk to life’ calculation is undertaken, grid datasets must also be provided for inundation times and flood hazard ratings.

If input grids represent depth above ground, an associated threshold level of depth above ground must be defined for each property.

If input grids represent depth above a datum, an associated threshold level of depth above the same datum must be defined for each property.

Grid format requirements

If flood depth / level is input via the grid method, grids must be:

In ASCII format, with file extension “.asc”
Of ascii ESRI type, as defined here: https://www.loc.gov/preservation/digital/formats/fdd/fdd000421.shtml

Producing grids from Flood Modeller

Flood Modeller provides tools for post-processing the 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 the “2dm_to_ascii.exe” program can be used. This is located in the “C:\Program Files\Flood Modeller\gui” folder and is run from the Command Prompt window.

Additional Grids for Risk to Life Calculations

If Risk to Life calculations are undertaken, two additional sets of grids are required. These must also be:

In ASCII format, with file extension “.asc”
Of ascii ESRI type, as defined here: https://www.loc.gov/preservation/digital/formats/fdd/fdd000421.shtml

The additional grids required are:

Type of Grid	Explanation
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).

Flood Data as Attributes in Property Dataset

In addition to inputting flood depth / level information via grid data, this can be input via columns in the property dataset. This technique can be used if:

A damage calculation update is required, and the original damage calculation is available but the original model grids are not
If a property dataset has been pre-interrogated against flood depth / level grids in GIS software.

Inputting flood depth / level information via columns in the property dataset can be achieved via the following steps:

1. Obtain or create property dataset containing flood level data for the required scenarios and return periods. No particular naming convention is required, but the user is likely to find the process simpler if names are provided which reflect the scenario and return period in question. An example of what a dataset may look like is shown below:

2. Tick the ‘use flood data in property file’ checkbox on the Calculation Information tab. The text at the top of the Events box will then change from ‘Depth Grids’ to ‘Property Depths’, and columns containing flood data can be selected from the dropdown menu, as shown in the image below. It is noted that the column headings (‘depth 2yr 2024’, etc) are available for selection. The return period and scenario year can be input manually:

Using Results in depth format or stage format

Grid or attribute data can represent either a water level (in mAOD) or water depth (m). The ‘threshold’ field in the property dataset must be populated differently depending on which has been used.

If the grid or attribute data used represents a water level (mAOD), a threshold must be provided which is also in mAOD, representing the distance of the building threshold above ordnance datum.
If the grid or attribute data used represents a water depth (m), a threshold must be provided which represents the distance of the building threshold above the ground. For example, this may be 0.15m for all properties.

Occupancy

This file provides average occupancy figures for each property type. These data are utilised in the optional risk to life calculation within Damage Calculator.

Data Source

The occupancy file was created by Jacobs using a number of publicly available sources, including: the "Employment Density Guide', 3rd edition, Homes & Communities Agency, November 2015; and "Review and Update of Occupancy Factors for UK homes", Public Health England, 2018. It is recommended that users check for updates before undertaking an analysis.

Required Format

Required columns are:

Name	Explanation
strMCMCode	Numeric entry that defines the residential or non-residential property type the data entry applies to. This code is cross referenced to property descriptions in “MCMCode.csv”.
blnPerBuilding	This is a TRUE / FALSE entry. It signifies whether the associated occupancy rate for the building type represents a total number of people (entry = “TRUE”) or an area per person value (entry = “FALSE”). For the latter, the number of people in a property is then calculated by dividing the specified property floor area by the occupancy rate.
dblOccupancyRate	This is a numeric entry that represents either the discrete number of people assumed in the associated building type or an area per person value (depends on blnPerBuilding value above). If the value is the latter, then the number of people expected in a property is calculated by dividing the specified property floor area by the occupancy rate. Note the area units assumed here should be the same as those used for property floor area data, which might not always be m2 (i.e. no unit conversions are performed in the tool).
dblOccupancyFactor	The occupancy factor is a numeric entry representing a percentage value. This factors the calculated people per property values. Accounts for not all occupants being in all properties at the time of flooding.

An example Image of Format Required:

PLPFactor

This file defines adjustment factors to be applied to depth damage data for one or multiple property level protection measures. It should be noted that factors have no currency data specified, and that damage Calculator has no function to carry out currency conversions. The damages calculated will assume the same currency as the specified depth damage datasets.

Data Source

This dataset is based on information contained in the DeFRA report ‘R&D Summary Report FD2607/TR1’

Required Format

Required columns are:

Name	Explanation
numPLPMeasure	Numeric entry specifying the measure index each data entry is part of, as listed in “PLPMeasures.csv”.
numDepth	Numeric entry. Assumed to be in same units as the depth grids used in Damage Calculator analyses, i.e. no conversions performed in tool (for MCM, depths specified in metres).
numFactor	Numeric entry. This is the factor to be applied at the associated depth to adjust the damage to account for the selected property protection measure. The impact of this factor can be seen in the Damage Calculator tool prior to starting a calculation. After switching on property level protection (by ticking check box on Calculation Information tab), two curves will be shown for each highlighted property type on the Depth / Damage Curves tab. One will be the original depth damage dataset and one will be the adjusted curve to account for the selected property level protection measure (selected in the Property Level Protection tab).

An example Image of Format Required:

PLPMeasures

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.

Data Source

This dataset is based on information contained in the DeFRA report ‘R&D Summary Report FD2607/TR1’

Required Format

Required columns are:

Name	Explanation
numPLPMeasure	Numeric entry providing an index for each measure defined. This is used to cross reference to property level protection factors listed in the “PLPFactors.csv” file.
strPLPMeasure	Text entry providing a (descriptive) name for each specified property level protection measure listed. The entries in this field will be listed in the Property Level Protection tab of the Damage Calculator interface, enabling a measure to be selected for use in the analysis
Comments	Text entry for user to optional provide additional descriptions of each specified measure. Field is required in csv file but entries can be left blank.

An example Image of Format Required:

RP DDcurves

This file lists the depth damage relationships for different types of residential properties.

Data Source

An example of this file (with one property type included) is provided in the Flood Modeller Damage Calculator example data. A file containing all property types is available with an MCM licence from FHRC.

Required Format

Required columns are:

Name	Explanation
CurveID	Numeric index cross referencing to scenarios listed in “MCM Depth Damage Curve Scenario.csv”, i.e. 1, 2, 3, etc.
Scenario	Text describing the storm scenario. The same text appears in “MCM Depth Damage Curve Scenario.csv” for the selected “CurveID”. Note: FHRC use abbreviated terms for their scenarios, e.g. "Short_NoW_storm" represents a short duration storm event (<12hrs) with no warning.
Year	Year the data is valid for (i.e. numeric entry). This references to the “Version” field in “MCM Depth Damage Curve Scenario.csv”.
MCM_code	Numeric entry that defines the residential property type the data entry applies to. This code is cross referenced to residential property descriptions in “MCMCode.csv”.
Depth	Numeric entry. This is assumed to be in same units as the depth grids used in the analysis. If the MCM is used, depths are specified in metres.
Domestic_CleanUp	Numeric entry specifying domestic clean-up cost at specified flood depth. This value is provided for information only and is not used by the Damage Calculator tool.
Household_Inventory_Damage	Numeric entry specifying household inventory damage value at specified flood depth. This value is provided for information only and is not used by the Damage Calculator tool.
Building_Fabric_Damage	Numeric entry specifying building fabric damage value at specified flood depth. This value is provided for information only and is not used by the Damage Calculator tool.
Total_Damage	Numeric entry specifying overall damage at specified flood depth.
Total_Damage_Square_Metre	Numeric entry specifying overall damage at specified flood depth converted to a per square metre value (could equally be a per unit area value). This field will be utilised by Damage Calculator, combining with property areas (or default areas – specified in another file, see below) to calculate total damages for each flooded property.

An example Image of Format Required: