HydroCAD® Stormwater Modeling - Since 1986
HydroCAD Supports DeepRoot Silva Cell 2™
HydroCAD provides direct support for the Silva Cell 2™, manufactured by DeepRoot. This allows the Silva Cell 2 to be easily used within any HydroCAD model for stormwater storage, detention, or infiltration.
The Silva Cell 2 can be modeled in HydroCAD-10.0 build 19 or later. The Silva Cell 2 replaces the original Silva Cell which was initially supported in HydroCAD-9.1 build 22. If you have an earlier version of HydroCAD, you must obtain a program update in order to model the Silva Cell 2.
How chambers are modeled
In a HydroCAD model, stormwater chambers typically appear as part of the storage definition for a "pond". In the simplest case, HydroCAD calculates the available storage for use with other calculations. But more often, it is used to generate a complete inflow or runoff hydrograph and route it through the pond. The resulting analysis indicates the water levels attained throughout the rainfall event, as well as any discharge that may occur through outlet devices or infiltration into the surrounding ground.
Special modeling considerations
Although the Silva Cell is usually filled with growth media (soil) to support tree plantings, it can also be used in an "empty" configuration for stormwater storage, detention, and infiltration. Each application requires a different modeling approach, as discussed below.
Modeling the Silva Cell without growth media
When used without media, the Silva Cell is typically modeled as a pond storage element, using the Silva Cell chamber definitions that are preinstalled with HydroCAD. These chamber definitions include the recommended 4" spacing between cells and allow for 93% void space, as stated by the manufacturer.
Setting up a pond to use Silva Cell chambers is a simple process: In the Chamber Wizard, select the Silva Cell from the drop-down list and set the number of rows and chambers-per-row. The Wizard will automatically layout the specified system and calculate the available storage. Since the Silva Cell is available in heights of 1 to 3 units, separate definitions are provided for each height.
For chambers that are installed in a stone bed, the Chamber Wizard allows you to specify the depth of the stone bed plus the stone voids (porosity). If applicable, you can also specify stone beside or above the chambers. With this information the Wizard automatically calculates the system dimensions and the storage contributions from the chambers and stone.
In addition to storage within the Silva Cell, HydroCAD can model almost any imaginable storage arrangement, such as auxiliary storage from adjacent pipes and catch basins, and even the above-ground areas (parking lot) that may provide overflow storage for certain events. Each "pond" can include an unlimited number of storage definitions as required to describe its overall storage characteristics.
Modeling the Silva Cell with growth media
When filled with growth media, water will not enter the Silva Cell as rapidly as a conventional open-cavity chamber, so a typical pond routing calculation will generally not be appropriate. Instead, the media-filled Silva Cell should generally be modeled according to the general guidelines for modeling bioretention areas.
Detailed Silva Cell information
For detailed chamber specifications and design information, please visit the DeepRoot Silva Cell page.
For more information about HydroCAD
Please see the following pages for further HydroCAD information:
Pond storage calculations
Images courtesy of DeepRoot Partners LP.
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