Working with Subcatchment nodes

A Subcatchment node must have an Urban Rain Gage Node node assigned to provide the inflow. All Subcatchment nodes within an urban network must have the same infiltration method defined, although different parameters (e.g. representing different land types/uses) can be specified within the method.

Click in the Name field, type a new name and press the Enter key on your keyboard to adjust the label provided to your junction. This is populated by default based on values set on the Model Defaults window, recall how to edit these defaults from the Urban Networks section.Note that if you change the name of a node, this label will be automatically updated in any connecting links so there is no further work to be done.

The X-coordinate and Y-coordinate are automatically filled based on the node location in the map view.

A Description and/or Tag can be optional provided. You may find tags helpful to group components together - this can be a way to categorise specific nodes. To edit these, click in relevant the field, type a new value, and press the Enter key

Click in the drop-down box and select the label of the Rain Gage providing the inflow to the Subcatchment node.

The label of the Junction node or Subcatchment node receiving the calculated runoff must be provided in the Outlet field. Click in this field and type the node name, then press the Enter key to store the change. Recall you must always save your urban network after any changes made.

The Area of the subcatchment is provided in acres or hectares. This will be calculated automatically when the subcatchment perimeter is drawn if the default area is set to zero in the Urban Model Defaults menu.

If you edit the vertices of your subcatchment perimeter, the area will not change. Manually adjust this value by clicking in the field, typing a new value, and pressing the Enter key.

The Width field provides the overland flow path for sheet flow runoff. The verage slope of the subcatchment, as a percentage, is specified in the % Slope field.

All of the Impervious parameters relate to the impervious areas of the subcatchment. A percentage of the land that is impervious can be provided, alongside the Manning's n value and depth of depressive storage for both the pervious and impervious parts. To change a value, click in the field, type your new value and press the Enter key to store the change.

The Routing options indicate internal routing within subareas of the subcatchment. In the Subarea Routing field, click the dropdown to select from:

PERVIOUS - route from impervious areas to pervious areas
IMPERVIOUS - route from pervious areas to impervious areas
OUTLET - route from both impervious and pervious areas directly to subcatchment outlet.

The Percent Routed specifies the percentage of runoff to be routed.

The Infiltration method to be used must be specified. By default, this will be set as per the Urban Model Defaults menu.

As mentioned above, please note the same infiltration method must be used for all subcatchments, and we recommend this is selected prior to building (and then not adjusted). Click in the Infiltration field to access the 3 dots to the right of the field. Clicking these 3 dots will open the Infiltration Parameters window for specifying the infiltration parameters to be used. Recall you must always save your urban network after any changes made.

You can specify Groundwater details for use within the urban simulation.

There are also various Unused parameters that cannot be specified in Flood Modeller at this time, however any previously defined methods will be unaffected. We refer the user to the Urban Subcatchment Node section of the technical reference for further details.