Stormwater Management Practices
Constructed wetlands treat stormwater physically and biologically.
- Biological removal occurs when plants take up pollutants through their root system, break them down and release them into the atmosphere.
- Physical removal of pollutants occurs as water moves slowly through the system as a result of resistance from plantings.
This is the process of redirecting rooftop runoff onto pervious infiltration surfaces, most commonly a lawn or garden.
- Disconnected Rooftop Runoff Areas. Rooftop disconnection involves directing flow from rooftop downspouts onto vegetated areas where it can soak into or filter over the ground. This disconnects the rooftop from the sewer/storm drain system and reduces both runoff and pollutants delivered to receiving waters.
- Disconnected Non-Rooftop Areas. Non-rooftop disconnection involves directing flow from impervious surfaces, such as driveways, streets and sidewalks onto vegetated areas where it can soak into or filter over the ground.
- Dry wells are normally gravel-filled trenches or pits capable of storing water on a temporary basis so as to allow enough time for the water to seep into the ground.
- Unlike most systems that incorporate vegetation to help address water management issues, dry wells rely heavily on the natural soil to take in water and control pollution.
Reduce stormwater runoff by capturing and storing rainwater which otherwise would land on an impervious rooftop and then run off.
- The structure must be able to handle extra weight.
- The roofs are designed to support plant growth and retain water only for plant uptake.
- Green roofs absorb heat and act as insulators for buildings, reducing energy needed to provide cooling and heating and reducing the "heat island effect" (U.S. EPA).
Infiltration berms are mounds of stone covered with soil and vegetation placed along gentle slopes to slow the flow of water and encourage stormwater infiltration.
- The main purpose is to slow the velocity of the flow and reduce the concentration of stormwater flows, reducing erosion and flood risk.
- Infiltration trenches are normally gravel-filled trenches or pits capable of storing water on a temporary basis so as to allow enough time for the water to seep into the ground.
- Unlike most systems that incorporate vegetation to help address water management issues, infiltration trenches rely heavily on the natural soil to take in water and control pollution.
- Micro-scale practices are used to capture and treat stormwater on-site in small areas, typically less than one acre in size.
- Micro-scale practices can be installed throughout an area to create a system that resembles natural drainage characteristics.
- Micro-scale practices include: Rain garden, Landscape infiltration and Micro-Bioretention
- Permeable pavements are alternatives to traditional paving materials such as asphalt, compacted gravel, or concrete.
- Permeable pavement systems consist of either segmented permeable pavers, porous concrete, or pervious asphalt.
- Permeable pavements reduce pollutant runoff into waterways by allowing the water to move through the pavement so that the stormwater percolates into the ground.
The two kinds of ponds are detention ponds, also known as dry ponds, and retention ponds, also referred to as wet ponds.
- Wet ponds experience fluctuation in water level due to precipitation and stormwater runoff.
- Dry ponds can have the appearance of a well-manicured landscape or natural looking landscape.
Rainwater harvesting is the practice of collecting and storing rainwater in large, durable containers, usually from rooftop gutters. Rainwater harvesting systems typically use a storage container such as a cistern, rain tank, or rain barrel for capturing rainfall for future use.
- Rainwater harvesting captures the first flush of stormwater, which contains the highest concentrations of pollutants.
Sand filters are typically a sand filled depression in the ground capable of treating and capturing pollution and excess runoff.
- Compared to the above ground system, the below-ground sand filter is well suited for highly urbanized areas.
- An above-ground or open sand filter requires a sizable piece of land and it is ideal for areas with less urbanization.
A submerged gravel wetland is a small-scale filter using wetland plants in a rock media to provide water quality treatment.
- Stormwater runoff is dispersed throughout the system, and releases at the surface.
- Pollutant removal is attained through biological uptake from plants, algae and bacteria within the filter media.
Swales are designed to channelize and move stormwater while slowing down stormwater flow and removing pollutants.
- Swales are ideal for use along roads and highways.
- Swales include: Grass swale, Wet swale, Bio-swale and Dry swales