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Several methods can be used to contain runoff water, allowing release
into the stormwater system after the storm is over or allowing the
natural processes of infiltration and evaporation to remove the
excess water.
- Dry Ponds are water detention basins
designed to collect runoff water from major storms, but remain
dry at other times. As they are deliberately designed to exclude
surface runoff during smaller storms, in much of the Bow River
Basin they must be provided with artificial irrigation to sustain
sufficient vegetation for most urban park uses. Dry Ponds can
be part of an effective integrated system where they protect downstream
ponds, wetlands, or other facilities from excessive flow rates
that might compromise treatment effectiveness. However, as typically
built in Alberta, they are relatively ineffective for water quality
treatment.
FIGURE 3.08 Dry stormwater pond (Heinz Unger)
- Detention Vaults are underground storage
devices (i.e., infiltration chambers under parking areas) for
runoff water, and may be useful where land is limited. Detention
Vaults are distinct from Oil, Grit and Floatables Removal Vaults,
which do not have a significant stored volume.
- Floodable Meadows and Thicket Areas
are natural features and designed imitations that can provide
temporary storage, while offering more effective treatment than
a Dry Pond. These meadows and thickets are analogous to the natural
floodplain vegetation that is tolerant of sustained inundation
and some sediment deposition. There is risk of sediment overload
if no upstream sediment control is provided.
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