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Click to download the Introductory [US units] tutorial model files.

Add Arch Chamber

Since CAD does not represent Stormwater Controls (i.e. Ponds, Swales, Raingardens) as richly in Plan as xpdrainage does, the Pipe Network that was imported is overly simplified and uses ‘dummy’ objects as placeholders for designers who are forced to split their work between several tools. To achieve proper Runoff Mitigation an Underground Detention Arch Chamber needs to be added, which can be easily done by converting the ‘dummy’ junction into a full Stormwater Control (SWC).

Right-click Standard MH (11) and select Change Template.


Select Arch Chamber from the Template list and change the Label name to Arch Chamber. Select OK to close the dialog.

Double-click or right-click and select Edit to review the Arch Chamber Stormwater Control (SWC) properties.This facility uses the Parabolic Arch Chamber configuration type and the individual Chamber section lengths, wall thickness, diameter and height are all as noted in manufacturer specifications. Any change to input which would affect the facility extents will be represented in Plan, just like any changes to the Plan layout will update dimension details within the SWC properties. Use the Click to Show Images icon in the lower left of the dialog to view a schematic of what the underground detention chambers looks like.

The embedded parameters allow for the fill material above and around the chambers to be applied toward facility storage. Notice that the schematic view of the detention facility can be switched from Plan (top down) view to a Section (or an on-end profile) view.

Under the Outlets tab, from the Outlet Type drop down list, select Orifice and enter a Diameter of 0.5ft and set the invert level to 167.3. This will set a 6in orifice 1.5ft above the base of the Chambers. Select OK to close the SWC dialog.

Reconnect System

Since xpdrainage allows for ‘AS-BUILD’ layout and details of stormwater systems, it is valuable to place the Inlets and Outlet of this facility at the real world proposed locations to ensure connection inverts, lengths, and slopes are accurate. Right-click the Arch Chamber SWC and select Specify Inlet/Outlet Location, select one of the Inlets/outlet. You can then drag and drop the Inlet/Outlet to the appropriate location. Repeat process for all objects until they are located as shown.

When the Pipe Network was imported any Junctions which fall on unconnected Inflow Areas are automatically connected to the adjacent Junction. If there are multiple Junctions imported on top of the same Inflow Area, only one will be connected, so it is important to review if all of the automatic connecting occurred as expected. In the case of Comm (3) and the Arch Chamber SWC, it appears that the Inflow Area connected automatically to the structure downstream of the Arch Chamber SWC. This can be easily updated by right click on Comm (3) and select Reconnect Inflow. Then place the inlet next to the parking island as shown.

Now that the Arch Chamber SWC has been configured, add a flow path as shown in order to view a Profile of the drainage system. Right-click the Flow Paths layer, select Add and click once on the Junction at the top-middle of the site then once at the downstream most Junction at the lower right corner of the site. Hit the Esc key to end the action, then right click on the Flow Path layer and select Show Profile.

Automatically Correct Data

Just like in the Plan view, the Flow Path shown in the Profile view can be zoomed into by using the mouse wheel and panned by using the mouse or by the view controls in the top left of the dialog. Notice in the Profile that while the Pipe Connections which were imported from GIS were brought into the software at the correct invert elevations the Junctions between pipes are not set to the correct elevations. Close or minimize the Profile view and under the Preliminary Sizing ribbon select Synchronize Manhole Invert Levels (Synchronize MH ILs). This will Automatically set the manhole inverts to the lowest connected pipe connection.

View the Flow Path Profile view again to see the corrected pipe network.

Size Pipe Network

Now that the Arch Chamber SWC has been added and configured, Automatically Size the Pipe Network within the Connections form by double clicking on the Connections Layer on the Tree View, or by select Connections on the Pipe Networks ribbon.


Pipe Networks can be sized based on Flow Paths - select a Flow Path from the drop down list and notice that the Connections list is sorted with Connections and Branch Lines based on the Flow Path selection. Sizing will occur for all Connections contained in the Flow Path and all Branch Lines. Select Pipe Sizing Wizard to perform preliminary sizing of the Pipe Network.

Once the Pipe Sizing Wizard is opened any previously defined Flow Path can be selected for sizing, including the entire Flow Path and all of its tributary branches. Since only one Flow Path has been created simply select Next to proceed to Pipe Sizing Criteria.

As the Pipe Sizing Wizard uses the Rational method for peak runoff flows based on the Preliminary Sizing input within the attached Inflow Areas, Select the Greenville IDF Table as the Rainfall Source and select the 10 year return period as the event sizing for the pipe network.  These Rainfall Sources can be reviewed under the Rainfall ribbon if desired.

A default Pipe Sizing Library has already been created and can be loaded by selecting the Open folder, then select NO when prompted about saving the current table. Select the US Default Pipe Library file, select Open. A list of typical pipe diameters and associated min/max design slopes will be shown. These may vary per manufacturer but these values will be used for the sake of the tutorial project.

Select OK to return to the Sizing Criteria dialog.

In this example project a design engineer has already laid out the desired invert elevations and slopes of the stormwater pipe network. In order to only size pipe diameters select Slopes and Invert Levels under the Lock dropdown menuSelect Next on the Pipe Sizing Wizard to proceed.

The Summary of Changes table will list the changes made to the network and by hovering over a highlighted value the previous value can be seen. As the invert elevations and slopes of the pipe network were locked only Diameter changes were made to accommodate incoming flow to the system, based on the Preliminary Sizing Inflow Area parameters and the constraints chosen in the 'Sizing Criteria' step of the wizard. Select Finish to apply updates and review a Sizing Summary Report.

Upon selecting Finish for the Pipe Sizing Wizard, by default the Pipe Sizing Report will be shown. There are several result formats to choose from, including the standard HEC-22 Preliminary Sizing Report format. Review the design results as desired and close the dialog when completed.

Validate System Data

For a system wide check for any potential discrepancies, under the Analysis ribbon select either Validate or Go – this will run an audit of the storm system and list any potential issues in the model.

While the Junction levels have already been corrected to match the Connection levels there is still a potential data inconsistency - Standard MH (1) has a sump (where the Manhole is deeper than any connected pipe). By checking the Levels box this inconsistency can automatically be updated. Additionally, when the Comm (3) Inflow Area was connected to a new destination the original Inlet specification is no longer applicable. Check the Connectivity box and then select Apply to automatic update these two items.

At this point all inconsistencies between the Junctions and the Connections have been noticed and automatically corrected. The Validate dialog shows no discrepancies are outstanding. Select OK to close the dialog.

Now the stormwater system is ready for full hydraulic analysis – browse to the Analysis ribbon and select Go to solve the model.