Detention basin property sheets (superseded)

The setting out of information defining detention basins has changed twice during the life of the DRAINS program. You might encounter older models that include basins set out in superseded formats.  DRAINS will still run with these, but it is best to update them.  This topic describes the older formats.

(a) The original basin format    

The original format included the outlet pipe details in the Detention Basin property sheet, as shown below:

This was satisfactory when the outlet pipe discharged into an open channel as shown above, but caused confusion when the outlet pipe connected to a pit and another pipe. It was necessary to insert dummy pipes or 'stubs' and many users specified outlet pipes twice (once in the Detention Basin and again as a pipe coming from this).

 The new property sheet format shown in the next section removed this problem by omitting the pipe specification, so that users were required to draw pipes coming from basins, thus clearing up the ambiguities.

(b) Revised format with an elevation-storage volume relationship

The second format is shown below:

In 2007 this was again changed, with the standard elevation-storage relationship being replaced by an elevation-surface area relationship.  This simplifies procedures for users because it is necessary to calculate areas in order to define volumes. DRAINS also applies an interpolation procedure instead of assuming straight-line segments in the elevation-storage relationship.

It is still possible to specify elevation-volume relationships for new projects, clicking the button for this in the Project Options property sheet opened from  the Project menu.

If a model contains a basin set out in the old format, any new basins added will also be in this format.  To change an older model to the elevation-surface area format, any basins in the model should be deleted.  The model then should be saved under a new name and you should exit from DRAINS.  After re-opening DRAINS and recalling the new model, it will be possible to draw the basins in the new elevation-surface area format.

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