Low Impact Development
Low Impact Development (LID) is a simple and effective strategy for stormwater
management. Instead of traditional techniques for controlling stormwater which
only aim to reduce peak flow rates, LID integrates green space, native landscaping
and natural hydrological functions to reduce pollutants and generate less stormwater
runoff from urban and developing areas. LID reduces runoff volumes by increasing
rainfall evaporation and infiltration into the soil and improving groundwater recharge
rates. LID can also include reusing stormwater for beneficial uses, such as lawn care,
instead of exporting it as a waste product down storm sewers. Proper application of
LID methods results in a hydrologic system that functions similar to that of the
pre-development environment, thereby decreasing non-point source pollutant runoff to
lakes, streams, and coastal waters.
LID not only improves the quality of our waters, but also adds aesthetic and economic value to the urban landscape by increasing open space, enhancing property values and improving recreational opportunities. LID is often less costly that conventional stormwater methods and is flexible as it can be applied to reduce a wide variety of stormwater and water pollution issues.
Some examples of LID tools:
Bioretention areas are engineered systems that provide storage for stormwater
runoff and facilitate water infiltration and the biological removal of pollutants.
Pollutants are trapped and treated by the soil and plants growing in the bioretention
area. These engineered depressions can be rain gardens placed in parking lot islands,
at the base of buildings to catch runoff from the rooftop, or vegetated swales at the
edge of paved areas. On residential lots, these areas are often called “Rain
Gardens”. Visit the
Sustainable Landscaping Extension webpage to learn more about this topic.
Permeable pavement is an LID option that reduces runoff by increasing
percolation through the paved surface. Often, this material is asphalt
with the fine particles left out, grids that are filled with course material
and planted with vegetation, or paving blocks that are spaced apart. Permeable
pavements are economical in that they reduce the need for expensive
stormwater infrastructure, and reduce overall flooding which can damage buildings
and roads. Permeable pavements are being used throughout the world to improve
the quality of surface waters and recharge local groundwater supplies. A URI
Extension publication entitled
"An Introduction to Permeable Pavement Alternatives"
provides a thorough overview of materials involved in this LID technique.
A powerpoint presentation outlining the porous pavement parking lot
at URI is available
here
.
More examples and case studies of pervious pavement use and reducing
runoff in New England can be found at the
UConn NEMO website.
Coastal Area Buffer Zones In Rhode Island,
coastal buffer zone regulations
in urban areas are changing to incorporate LID concepts and techniques, and encourage
on-site stormwater management and the creation of urban “greenways”. The
URI Cooperative Extension Education Center is developing a certification program
for landscape professionals working in coastal areas that will include topics such
as LID site assessment, design and installation. Visit the URI CE Healthy Landscapes
Website to learn more about
shoreland buffers.
Green Roofs A roof with plantings is
an LID practice that can improve nitrogen removal from rain, reduce stormwater
runoff and neutralize acid rain. In addition, green roofs are aesthetically
pleasing, reduce the city “heat island” effect, reduce winter
heat demand, lengthen roof life, and provide songbird habitat. The
Whitney Water Purification Facility and Park
in
Connecticut is the largest green roof in the state. This green roof has improved
the building’s
insulation, significantly reduced stormwater runoff and has decreased
the area’s
heat island effect.
Site Planning The
Jordan Cove Watershed Project
is a ten year study designed to investigate the water quantity and quality
benefits associated with the used of LID techniques in an urban/suburban
subdivision. This site demonstrates the use of several LID practices,
including pervious pavement, rain gardens, cluster development, and rain
barrels coupled with homeowner education. The
UConn Extension LID stormwater treatment practice database
contains
an interactive map and a searchable database on stormwater treatment practices
in the state of Connecticut.
Simple ways to incorporate LID:
- Reduce impervious cover
- Create opportunities for rainwater and stormwater runoff to collect and infiltrate into the ground
- Minimize disturbance
- Preserve and recreate natural landscape features
- Incorporate small-scale LID practices throughout the landscape
- Use
a rain barrel (visit URI CE for more info)
- Replicate the natural hydrology of a site