How to create 1D reservoir units from a map

This section provides a step by step guide on generating 1D reservoir units.

1. Load ground data.
   A ground grid, i.e. digital elevation model (DEM) from LiDAR data, is required to be loaded into the viewport. This must be a compatible grid format, i.e. binary (flt) or ASCII (asc). On the Home tab, click Add GIS Data and browse to your grid.
   The grid provides the vertical elevation data for the new reservoir units. These data are used to define the surface area to depth relationship required by Flood Modeller.
   It should be noted that the ESRI grid format is not compatible for use in reservoir unit generation. However, the layer converter tool in Flood Modeller can be used to create a compatible grid from an ESRI grid.
2. Define reservoir polygons.
   If a shapefile of reservoir polygons already exists then this can be loaded into the viewport. Click on the Add GIS Data in the Home tab (within GIS Data section).
   
   If there is no existing polygon shapefile available that represents the required reservoir then a new shapefile can be defined by drawing directly on the Flood Modeller viewport. On the Home tab within the GIS Data section click on the New button and select Shapefile from the drop-down menu. Then select to draw a new polygon shapefile from the presented options. When drawing a polygon which represents your reservoir, draw in a clockwise direction as this represents a shape (anti-clockwise represents a hole). Refer to How to create a new shapefile for guidance.
   
3. Access reservoir unit function.
   Click the Reservoir button in the Map Tools tab of the main toolbar.
   
   Alternatively, from the Toolbox, select:
   Additional Model Build Tools / 1D Networks / Run Reservoir Generator
   
4. Specify reservoir unit shape and grid data files.
   
   The 1D reservoir tool will calculate contours based on elevation levels from a ground level grid and use this to establish a surface area to depth relationship. The tool requires the following parameters to be set to perform this operation:
   • The name of the polygon shapefile that represents the new reservoir outlines (this is the outline of the maximum extent of the reservoir). All polygon shapefiles loaded into the project are available to select from.
   • The name of the grid to provide the underlying ground elevation data. All compatible grid datasets loaded into the project are available to select from.
   Enter your shapefile and ground data grid file into the fields provided by selecting the relevant file (loaded into the Layers panel of Flood Modeller) or click the button to the right to browse using standard Windows file explorer.
5. Select the upper and lower levels
   Click Calculate Levels . This will calculate the minimum and maximum ground level for each of the polygons specified in the shapefile, based on the ground elevation data given in the grid data file:
   
   At this point, you should adjust the minimum and maximum levels as required. The tool provides the following options to enable customisation of the minimum and maximum levels:
   
6. Select node labelling
   The Label assigned to each reservoir can be selected from the attributes specified in the shapefile defining your reservoir areas. Select the label you would like from the drop-down list provided. When selected, the new labelling will automatically be applied to each reservoir in the table showing the minimum and maximum levels.
   
   Alternatively, apply labelling to each reservoir individually by double clicking on the label name in the table and entering free text.
7. Define contour settings
   The tool will calculate contours from the minimum level specified for each reservoir and use this to establish a surface area to depth relationship. The number of contours (vertical steps) to use in the surface area to depth relationship can be specified in two ways:
   1. a fixed number of contours - Flood Modeller calculates the step size between minimum and maximum reservoir levels. The default is 25 contours but this can be edited.
      Note that a total of N+1 levels will be considered: the minimum level followed by the N contours, with the Nth contour height equal to the maximum reservoir level specified.
   2. a fixed contour step size in metres - Flood Modeller calculates the number of contours required between minimum and maximum reservoir levels. The default is 10 metres but this can be edited.
      Note that in this instance, the tool will perform calculations at the minimum reservoir level specified and then at each “step” defined (the minimum level plus N metres, the minimum level plus 2N metres, etc.) provided these “steps” are calculating at levels lower than the maximum reservoir level. A final calculation will be performed at this maximum level (regardless of whether the maximum level is the minimum level plus a certain number of “steps”)
   A check-box is provided to allow the option of including a glass wall to your model. If a glass wall is not included and water levels exceed the maximum level given for the reservoir, instabilities will be caused which potentially could stop the model from running. Therefore, including a glass wall is an optional setting that Flood Modeller uses to improve the stability of models. To include a glass wall, ensure the Include glass wall check-box is ticked and enter the height of the glass wall (in metres) in the field provided. If you choose to include a glass wall, a final contour will be included for each reservoir at the top of the glass wall.
   
8. Calculate the contours
   Click Calculate to calculate the contours for each reservoir. The second table will then be populated with the depth, area and volume calculated at each level. Note that the settings defining the minimum and maximum levels and the specification of the contours can be adjusted after the contours have been calculated, however the tool is setup to enable these to be defined initially as the calculation of the contours can take some time.
   The text above the table indicates which reservoir the parameters relate to. Click on a different reservoir in the first table to highlight it and view the parameters for that reservoir.
   Note that the calculation can take some time (depending on number of contours, resolution of the ground data grid, etc.) and always takes longer with non-binary grid data, i.e. ASCII text grid data.
   
9. Make final adjustments to settings
   At this point you can specify different levels at which you want the contours calculated by double-clicking in the Level column on the row you want to change. A level can then be manually entered for this row. Clicking elsewhere on the tool will then cause the recalculation of all contours for the reservoir.
   If you choose to change any of the settings for the minimum and maximum levels or the contour settings, the Calculate button will become re-enabled. Click Calculate to recalculate the contours when you are happy with your adjustments and this will enable the Save button.
10. Save to IED format
    When your contours have all been calculated, the Save button should be enabled to allow you to save your settings. If the Save button is disabled, changes have been made but the new contours not yet calculated. Click Calculate to recalculate the contours and enable the Save button.
    Click Save to save your settings in IED format. You will be prompted to choose a name and location for this file. Alternatively, click Close to cancel out of the reservoir unit window without saving any changes.