The Cascade command lets you route the current inflow
hydrograph through a short cascade of
storage cells formed from a variety of cross-sectional shapes such
as pipes, rectangular boxes,
horizontal and vertical elliptical pipes and pipe arch sections.
The storage may be provided by a ‘superpipe’ or oversized storm
sewer with a modest slope and a reach length limited to 100 - 150m
(330 - 500 ft). Two reaches of superpipe can be used in series.
Each chamber is horizontal with a specified length, width,
height and invert elevation.
The outflow control from each chamber is assumed to be an
orifice of specified diameter and
coefficient of contraction with the orifice invert equal to the
bottom of the upstream chamber.
You can specify a pipe, box or any of three special pipe
sections (e.g. horiz elliptical, vert elliptical or pipe arch).
If you select the special pipes a drop-down list lets you browse
through a set of commercially available sizes. These are shown in
metric or imperial sizes depending on the choice of units.
If a cell is surcharged, the data box containing the Height is
highlighted to warn you that more
storage or a larger orifice is required.