Drainage

1. A stormwater basin is a large water body that receives runoff from streets and parking lots. The
basin slows (attenuates) the flow of storm water and sometimes treats it by reducing sediments
or phosphorous from runoff. The basin is a part of a larger system of land development
practices, including stream restoration and other landscape measures.
The design of the basin is influenced by the hydrology of the site, including pre-development
and post-development conditions, to achieve the desired goals of storm water management.
The basin must be large enough to retain a reasonable percentage of the increase in
impervious surface from development. If a larger basin is not feasible on a site, then other
design practices might be used.
For example, rain gardens that capture and infiltrate storm water runoff might be used instead of
a basin. The location of a basin can be influenced by existing topography, or it might need to be
built in close proximity to nuisance flooding areas that occur frequently on the site.
Basins can be designed to function as wetlands and provide significant benefits of wetlands
such as habitat for wildlife, flood control and soil stabilization. They can also be designed for use
as recreational spaces.
The design of the plantings in and around a basin can be a complex process, often involving a
team of professionals. Careful planning begins with a scaled drawing of the site, and accurate
measurements are important to ensure a healthy and successful planting.
The Benefits of Stormwater Basins
Stormwater Drainage
A stormwater basin, also referred to as a wet detention pond or an infiltration pond, is a man-
made area of graded earth that’s designed to manage stormwater runoff. Unlike natural ponds
that hold water continuously, a stormwater basin typically holds the water temporarily after a
rain event and then empties it out at a controlled rate to avoid flooding and erosion. These
ponds are designed to protect against flood damage, serve as an artificial wetland and improve
the water quality of adjacent bodies of water.
As urbanization increases, stormwater runoff can overwhelm city sewer systems and cause
significant erosion and flooding on downstream properties. The use of traditional drainage
methods such as basins has been successful at reducing flood peak flows, but the practice
often increases soil infiltration and stream erosion rates. These conventional techniques have
limited water quality treatment and often require a large area of valuable land that could be used
for development.
Wet detention and infiltration basins offer a more sustainable alternative to conventional
drainage solutions. In addition to preventing flood damage, they can provide environmental
benefits by reducing sediment and pollutants in the water. However, they also require a lot of
maintenance such as regular mowing, the repair of eroded slopes and periodically checking that

2. the outfall pipes are not clogged or blocked. In addition, the ponds can become breeding
grounds for mosquitoes and have been known to emit unpleasant odors as rotting leaves and
other debris build up.
Landscaping Ideas For Stormwater Basins
Stormwater Basins are pond-like structures that convey and store stormwater during storm
events. They are designed to reduce the peak flow rate from developed land.
They improve water quality by removing nutrients from the stormwater. There are two kinds of
basins: dry detention basins and wet detention/infiltration basins. Both require maintenance to
function properly.
Drainage
Unlike the sewage drains that get rid of the waste from your toilet, shower and kitchen sink,
storm water drainage systems are not connected to the city’s sewer system. Instead, they carry
storm water and rainwater from paved areas directly to lakes, rivers and oceans.
As you can imagine, this runoff is contaminated with oil from car drippings, soap and detergents
from washing your driveway and lawn chemicals and sediments from industrial sites and
residential neighborhoods. This polluted storm water carries bacteria and viruses that can make
you sick. Swimming in such waters can result in earaches, sinus problems and diarrhea. The
pollutants also harm aquatic life.
Stormwater drainage systems are designed to divert as much of this dirty runoff away from the
foundations of homes and buildings, as well as roads and sidewalks. They generally follow the
natural topography of a site and are aimed at a nearby drainage basin.
There are many different ways to accomplish this. Some cities install open storm drains that
have long, uncovered channels to carry free-flowing water. They’re inexpensive to set up but
require constant monitoring as they can collect hazardous materials that may wash into the
system. Others create permeable, grassed swales that slow the flow of water and allow
contaminants to be filtered naturally before reaching the aquifer. Narrow, stone-filled trenches
are another type of shallow, drainage canal that can help filter the runoff.
Vegetation
The use of native plants in the various landscaping zones around a basin can add significantly
to its overall attractiveness. In addition, these plants provide habitat for wildlife. The vegetation
in the wetland zone (above the water's edge) should be composed of a mixture of rigid and
linear species, such as rushes or sedges, and a few floating-leaf plants such as water lilies,
pickerel weed, and arrowhead.

3. The plant species in the wet meadow zone (in the area below the surface) and the prairie zone
can be more varied, depending on the site. A mix of native grasses and wildflowers is usually a
good choice. These species should compete successfully with the invasive weeds that can be
found in wet soil conditions.
In the upland zone, the choice of species will depend on the final function of the area. It could
be a walking trail, or it could be left to naturalize into a grassy meadow. If it is intended to be a
wildlife habitat, grasses and short flowering prairie plants are appropriate.
All storm water basins require some maintenance, such as clearing debris after heavy rains and
checking the outfall for any problems or damage. However, a basin with native plants in place
will need to be mowed less frequently—sometimes only once per year—than a traditional lawn
would.