Adding Subcatchments

Civil Designer allows the user to graphically enter the subcatchments for stormwater design.

This function allows you to create subcatchment runoff areas by defining the area graphically by drawing a polygon and giving it an identifying name. The program will save all the vertex coordinates together with the subcatchment name. The subcatchment can then be linked to a specific Node record of which the runoff area will be updated to the calculated size of the subcatchment. The drainage path can be indicated graphically and the drainage length and a weighted average slope will be calculated and entered into the Runoff time calculation. The subcatchment can also be displayed graphically by specifying the subcatchment settings in the Display settings. If you have deleted records, they appear in the Node Data dialog in grey scale.

In this example, we will be creating a Subcatchment that will drain to node 70.

Graphical Menu › Add Subcatchment

The program will prompt:

Subcatchment Perimeter: Indicate start point


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)


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


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


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)


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)


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.

print print friendly version         


 
Knowledge Base OTHER TECH TIPS | CIVIL DESIGNER HOMEPAGE     

CIVIL DESIGNER is a registered trade mark of Knowledge Base (Pty) Ltd, Developers of Professional Civil Engineering and CAD Design Solutions.