Each Stormwater Controls - SWC has an associated sizing calculator that allows you to:
- Specify a new volume for the Stormwater Control whilst varying a chosen dimension, e.g. Depth, Width, Length etc.
- Specify a scale factor to modify the existing volume of the Stormwater Control, again whilst varying a chosen dimension
- In the case of a Tank or Pond to specify a particular side slope, either from its top downwards or base upwards
The SWC sizing calculator consists of the following options:
Method
Choose Quick Storage Estimate, Runoff Reduction Volume, or Methode des Pluies to specify a volume in the field below (please note, Methode des Pluies may not be available for your region). When choosing any of these options, a calculator button appears to the right of the Volume field. If Quick Storage Estimate is chosen, then clicking the calculator button produces the Quick Storage Estimate Calculator (QSE). If Runoff Reduction Volume is chosen, then clicking the calculator button produces the Water Quality Calculator (WQv). If Methode des Pluies is chosen, then clicking the calculator button produces the Methode Des Pluies Calculator.
Using any of these calculators will return a volume into the sizing calculator. In the case of the QSE calculator, the returned volume is the center of the estimated storage volume range. In the case of the WQv calculator, the returned volume is the Target Volume stated in the WQv calculator's report. For the Methode des Pluies calculator, the returned volume is the maximum storage volume. Using the Quick Storage Estimate option also allows you to manually enter the desired volume rather than using the calculator.
For phases containing only Baseflow or Input Hydrographs, the following options are not available: Quick Storage Estimate, Runoff Reduction Volume, and Methode des Pluies.
Design Up To
This is applicable for all Methods except Side Slope - relevant to Tank and Pond SWCs only. Choose the Elevation that the volume will be provided up to:
- Exceedance - The Exceedance Elevation of the Stormwater Control.
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Freeboard - The Freeboard Elevation of the Stormwater Control. i.e. Exceedance Elevation - Freeboard depth.
Note: Where the freeboard is not specified the Exceedance Elevation will be used. -
Lowest Outlet - The Invert Elevation of the lowest outlet with a control specified.
Note: If the control Invert Elevation is below the Base Elevation of the structure (or Ponding/Swale in a Bioretention/Swale) the control will not be considered. If there are no outlets the Exceedance Elevation will be used.
Update
This is applicable for all Methods except Side Slope - relevant to Tank and Pond SWCs only. Choose a parameter that is to be updated when theSWC is resized to the new volume. This list is specific to the type of SWC. Most of the options are self-explanatory, e.g. Length, Width, Base Elevation etc.
Two options perhaps needs a little more explanation:
- Areas (for Pond and Tank only). Choosing this option results in the cross-sectional area for each entry in the Tank / Pond's Depth / Area / Perimeter spreadsheet to be scaled by the same scale factor to achieve the specified volume. In addition, the Perimeter value for each entry in the Depth / Area / Perimeter is set to the circular circumference of its new area.
- Number Of Dry Wells (for Dry Well only). Choosing this option results in the Number Of Dry Wells parameter being set to the minimum no. of dry wells of the current dimensions that are required to satisfy at least the specified volume.