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Click on a position in the Design Centre window and
the following prompt is displayed:
Subcatchment Perimeter: Indicate next point (Click
near start to end)
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Continue indicating perimeter points and end by
clicking on or near the starting point again. The
program will prompt:
Add Subcatchment: Input new subcatchment name
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In this example the subcatchment will be named C 70.
Once the subcatchment has been named, the program will
prompt to indicate the node the subcatchment must
drain to, click on node 70.
Select the node that subcatchment C 70 must drain to
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Once the drainage node has been selected the user must
confirm the selection.
Click Yes to accept or No to select
another node.
Define the paved drainage path in the upstream
direction (Right click to end)
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There will be a line attached to the cursor running
from node 70. Draw the drainage path from the node in
an upstream direction to the most remote point of the
catchment. A confirmation dialog will open asking if
you are satisfied with the drainage path. Click on
Yes if satisfied with the path else click on No
and redefine the path.
If there is a problem with the drainage path, an error
message will appear.
Two drainage paths need to be defined for the Illudas
runoff calculation method. The first for the paved
runoff area and the second for the grassed runoff
area. The paved drainage path will be drawn in a solid
line and the grassed drainage path in a dashed line as
displayed in the picture below.
Define the grassed drainage path in the upstream
direction (Right click to end)
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The runoff time calculator dialogs will open
according to the specified runoff calculation method.
Illudas Method:
The Paved Area Entry Time Calculator dialog will
open with the Length and Slope entered as calculated
from the defined drainage path.
Click on OK and the Grassed Area Entry Time
Calculator dialog will open with the Length and Slope
entered as calculated from the defined drainage path.
Enter the Manning Factor and adjust the Length and
Slope if required.
Click on OK. The Runoff page for node 70 will
open with Subcatchment C 70 selected and the Paved and
Grassed Entry Time updated.
Click on Close.
Rational Method:
The Time of Concentration dialog will open with the
Longest Length and Average Slope entered as calculated
from the defined drainage path. Enter the Flow Type
and the Roughness Coefficient and adjust the Length
and Slope if required.
Click on OK. The Runoff page for node 64 will
open with Subcatchment C 70 selected and the Time of
Concentration updated.
Click on Close.
Wallingford Rational Method:
The Wallingford Time of Entry dialog will open with
the Overland Flow Length and Slope entered as
calculated from the defined drainage path.
Click on OK. The Runoff page for node 64 will
open with Subcatchment C 70 selected and the Time of
Concentration updated.
Click on Close.
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