This step is only required if using duration and arrival time grids in place of hydrograph data. Duration grids are only required for agricultural damages. If agricultural damage is not part of the assessment then duration grids do not need to be prepared. Arrival time grids are required for both agricultural and life loss calculations.

Duration grids and arrival time grids are generally produced from either ArcGIS® plug-ins or RAS Mapper. The duration grid is defined as the duration of time a grid cell is wet. The arrival time grid contains the amount of time it takes for water stage to reach a predefined threshold at each cell. Typically the arrival time threshold is two (2) feet. If life loss calculations are to be computed with arrival time grids, make sure the threshold for arrival time (default of two feet) is the same threshold used to define the hazard boundary for each scenario.

For an agricultural damage assessment, the arrival time threshold is typically zero (0) feet.

Duration Grid Preparation

To convert the duration grid to binary format (.flt):

  1. Start ArcCatalog. The ArcCatalog window opens.
  2. If the ArcToolbox Pane is not present, click ArcToolbox on the Standard Toolbar and the ArcToolbox Pane displays in the ArcCatalog window.
  3. From the ArcToolbox Tree, double-click Conversion Tools, double-click From Raster, and then double-click Raster to Float.
  4. The Raster to Float dialog box opens (Figure B.4). Browse to the location of the duration grid file by clicking next to the Input raster box.
  5. The Input raster browser opens (see Figure B.5). Browse to the location of the duration grid file, click on the duration grid filename. Click Add, the Input raster browser closes, and the path and the name of the selected duration grid file ( i.e., E:\projects\FIA\westfork\Duration\FP_Fail \FP_F_Duration) appears in the Input raster box on the Raster to Float dialog box.
  6. By default the software creates the output floating point raster file to the same directory as the selected duration grid file. In the Output floating point raster file box the path and the default name for the binary file (i.e., _E:\projects\FIA\westfork\Duration_
    FP_Fail\RasterT_FP_F1.FLT) appears. Modify the float filename to represent the flood scenario represented by the duration grid (i.e., FP_Fail_Duration.FLT).
  7. Click OK, the Raster to Float dialog box closes. The Raster to Float Compute dialog box opens. This dialog box notifies the user of the status of the compute and how long it took to create the binary file. When finished viewing information, click Close. The Raster to Float Compute dialog box closes.
  8. Now in the selected directory, there are two files, *.flt and *.hdr. The duration grid has been successfully converted to a binary format.

Arrival Time Grid Preparation

To convert the arrival time grid to binary format (.flt):

  1. Start ArcCatalog. The ArcCatalog window opens.
  2. If the ArcToolbox Pane is not present, click ArcToolbox on the Standard Toolbar and the ArcToolbox Pane displays in the ArcCatalog window.
  3. From the ArcToolbox Tree, double-click Conversion Tools, double-click From Raster, and then double-click Raster to Float.
  4. The Raster to Float dialog box opens. Browse to the location of the arrival time grid file by clicking next to the Input raster box.
  5. The Input raster browser opens. Browse to the location of the arrival time grid file, click on the grid filename. Click Add, the Input raster browser closes, and the path and the name of the selected arrival time grid file appears in the Input raster box on the Raster to Float dialog box.
    6.By default the software creates the output floating point raster file to the same directory as the selected arrival time grid file. In the Output floating point raster file box the path and the default name for the binary file (i.e., _E:\projects\FIA\westfork_
    ArrivalTime\FP_Fail\RasterT_FP_F1.FLT) appears. Modify the float filename to represent the flood scenario represented by the arrival time grid (i.e., FP_Fail_
    Arrival.FLT).
    7.Click OK. The Raster to Float dialog box closes and the Raster to Float Compute dialog box opens. This dialog box notifies the user of the status of the compute and how long it took to create the binary file. When finished viewing information, click Close. The Raster to Float Compute dialog box closes.
    8.Now in the selected directory, there are two files, *.flt and *.hdr. The arrival time grid has been successfully converted to a binary format.