How to use the Export Maps tab of the 2D Flood Calculator

Within the standard flood map export tab of the 2D Flood Calculator a number of options exist allowing you to tailor the flood map calculation to their specific needs. These options are:

• A list of the 2D Model Results - This section shows all compatible 2D model result datasets currently present in your map view. These datasets automatically populate the 2D Model results list box

• Select output file name and type - The output file button (located in the lower right corner of the window), prompts you to select the destination folder and filename for your output file (default option is an .asc file).

  Note that this is only a base name, which will then be used for multiple output files if multiple time steps have been selected from the time steps list (see below). Individual output filenames are composed of the base name plus an increment which is equivalent to the selected time step number, e.g. if 'MyFlood' was specified and the time step '02' has been selected in the Time Steps section, then the file produced will have the name 'MyFlood.02m.asc'. If multiple time steps have been selected, then the 2D Flood Calculator will automatically cycle through all requested calculations in a single batch operation.

• Select Time Steps - All model results assigned to the selected 2D Model Results file are listed on the export maps tab, with each one signified by a time step number. Clicking on a time step in the list selects the particular result to be converted to a flood map. You can select multiple items from this list by holding the Ctrl key while clicking, and separate output files are then created for each time step selected. The multiple filenames are defined using the user specified base filename combined with the corresponding result time step number. Note that you can select the pseudo time steps available for the selected 2D output parameter in this tool, e.g. “9999” represents the maximum values occurring in each cell throughout the simulation period.

• Impose Range of Water Levels - The lower and upper limits of any calculation can be specified. The default flood depth limits in a flood extent calculation are 0m to +100m. Water depths that are outside of these limits will be ignored and not written to the output file. To change these values tick the box adjacent to the limit value to be changed. A new box is then displayed in which you can type a new limit value in metres (click on the box to start typing).

• Specification of output data type. The Export Maps/Grids panel provides the following options for defining content of your output grid(s):

  • Export 2D model results for selected time steps as separate flood maps (default setting)

  • Produce a hazard map output. This is a map output produced using a combination of flow and volume 2D results (so both must be available in your map view). Selecting this option you are also required to set a debris factor and, if a varying debris factor is specified, also select a land use type (Arable/Pasture, Woodland or Urban types).

  • Extract 2D model grid. This option extracts the ground grid embedded in the 2D results files as a separate raster dataset. No flood data is extracted from the results files with this option.

• Load to View – ticking this box (located in the lower left corner of the window) instructs Flood Modeller to automatically load the output produced into the Layers panel.