How to add a hydrological boundary to a model


Hydrological boundaries can provide boundary inflow data to either a 1D or 2D model. They utilise hydrological parameters and rainfall-runoff processes to produce inflow hydrographs in a format compatible with your model. Flood Modeller includes a number of different boundaries, each one incorporates a different rainfall-runoff calculation method. These are as follows:

Further technical information on these methods can be found in the technical reference section of the user guide (Hydrological Boundaries).

This section details the procedure for adding these node types to your 1D and 2D models.

1D Modelling

  1. Load the 1D network you wish to work on into the project view and make it the active network so it also appears in the map view and network table (right-click in the project view and select Set Active from the displayed menu). Alternatively if you are starting a new model build select the new network button in the Home tab of the main toolbar to specify a network name and save location.
  2. Specify the position within the network where a new node will be added. If your network already contains one or more nodes then highlight in the network table the node below which you want the new node to be located. If you are adding a node at the upstream end of a network then you can select the top row in the Network table, entitled “General”. 

    Useful tip: Boundary nodes can be located out of position, all together at either end of a network. The labels specifying connecting nodes will determine the true position of the node both when it is drawn with links on your map and when you run a simulation with your network.
  3. Select which hydrological boundary you wish to add. These can be selected from the Hydrology tab of the main toolbar. You can also select these node types from the 1D Build tab, where they are listed as types of flow boundary node.

  4. After selecting a node type your map cursor should change to a pencil icon to signify draw mode. Click on the map at the desired node location to add a new node. Take care to only click once on the map as each click while in draw mode will add another new node. After adding a hydrological node Flood Modeller will prompt you to provide a node label by displaying the following window:

    After defining a name and clicking OK the node will be added to the network table, nodes list table and map simultaneously. The name you select should also be shared by the hydraulic node receiving the inflow from the hydrological node, e.g. a river section. When you save the network the nodes sharing the same name will then be shown connected.

    To deactivate the draw mode click the selected node type a second time, select Stop from the map right-click menu, click on the Select mode icon in the map control bar or just press the Esc key. Alternatively selecting a different 1D node type will switch the draw mode to add other node types.

    It is also possible to add hydrology nodes to your network using the menu accessed by right-clicking on the Network table. First highlight the node upstream from your new node, then select Insert > New unit from this menu. A new window will be displayed enabling you to select any node type including hydrology boundaries, as shown below. You will then be prompted to provide the necessary node labels as described above.

2D Modelling

Hydrology data for a 2D model can consist of one or more boundary inputs of rainfall or infiltration data applied over a user defined area (within your 2D domain). Note that evapotranspiration or groundwater infiltration inputs will be negative, i.e. drawing water from your flood flows. These hydrology data are optional for a 2D model and do not have to be specified (provided you include some other form of input boundary, e.g. flood depth, flow time series or linked 1D model)

The procedure for defining hydrological boundaries in a 2D model is as follows:

  1. Load the 2D model simulation file (xml file) you wish to work on into the project view and make it the active simulation by highlighting in the project view (click on the filename in the project view). Alternatively if you are starting a new model build right-click on the simulations section of the project view and select new 2D simulation from the displayed menu to specify a simulation name and save location.
  2. Access the 2D model definition window by double-clicking on the appropriate simulation name in the project view (or right-click on the simulation name and select Open from the displayed menu).
  3. Select the Domains tab and then the Rainfall/Infiltration sub-tab on the 2D model interface. The display should be as follows:

  4. Click the Add button to define a new hydrological boundary. A new window is displayed prompting you to define the details of the new boundary data source, as shown below.

    Hydrology boundaries consist of a time series dataset and a polygon shapefile defining the area over which the data will be applied. The shapefile is specified using a browse button or by dragging a layer from your Project or Layers windows. The following options are provided to define the associated hydrological time series:

You can specify multiple hydrology input areas, i.e. separate polygon shapefiles. However, each one must be defined as a separate item associated to separate time series datasets.

  1. You have the option to introducing a spatial loss component for your hydrological input. This can be in conjunction with a rainfall/infiltration dataset or as a standalone boundary data source. A detailed definition of spatial loss components is provided elsewhere in the user guide.
  2. The units of time and rainfall/infiltration data must be specified separately for each hydrological boundary added to your model. The boundary definition window provides dropdown lists of available units for each parameter (as shown in the screenshot above). Available time units are days, hours, minutes and seconds. Available rainfall/infiltration units are mm/hr, m/s and in/hr. Your input data must be in one of these unit options (or you will need to convert it before adding to your model)
  3. After adding a hydrological boundary to your model it will appear listed as a hydrology source in the main 2D interface as shown below:

    You can further edit any property of an existing boundary in this table. Click on the cell to be edited and you will be able to either browse to a different file or select a different option from the provided dropdown list (edit option depends on the cell selected). If you have specified a manually entered time series then you can edit any value in the right hand table by clicking on the cell and typing in a new value.
  4. When you have defined all required hydrological data sources for your 2D model click the Save button in the main 2D interface to ensure all changes are stored.