Low Impact Development Manual for Michigan - OSEH - University ...

Flow inlet: Curbs and curb cuts
Curbs can be used to direct runoff from an impervious
surface along a gutter to a low point where it flows
into the rain garden through a curb cut. Curb cuts may
be depressed curbs (Figure 7.8), or may be full height
curbs with openings cast or cut into them.
Figure 7.8
Curb cut into bioretention area/rain garden
Source: Huron Pines
Positive overflow
A positive overflow, via the surface or subsurface, is
recommended to safely convey excessive runoff from
extreme storm events.
Positive overflow: Domed riser
A domed riser may be installed to ensure positive,
controlled overflow from the system (Figure 7.9). Once
water ponds to a specified depth, it will begin to flow
into the riser through a grate, which is typically domed
to prevent clogging by debris.
Figure 7.9
Positive Overflow Device: Domed riser at
Macomb County Public Works Office
Source: Macomb County Public Works Office
Positive overflow: Inlet structure
An inlet structure may also be installed to ensure positive,
controlled overflow from the system. Once water ponds to
a specified depth, it will begin to flow into the inlet.
Applications
Bioretention areas can be used in a variety of applications,
from small areas in residential lawns to extensive
systems in commercial parking lots (incorporated into
parking islands or perimeter areas). Industrial, retrofit,
highway/road, and recreational areas can also readily
incorporate bioretention. One key constraint in using
bioretention in ultra-urban settings is space.
Residential
The residential property owner that wants to design and
build a rain garden at home does not need to go through
the engineering calculations listed under stormwater
calculations and functions. Assistance with simple rain
gardens is available from several sources listed under
the Plant Selection portion of this BMP.
Figure 7.10
Single-family residential lot drainage schematic
Claytor and Schueler, 1995 with modifications by
Cahill Associates
LID Manual for Michigan – Chapter 7 Page 136