Low Impact Development
Low Impact Development (LID) is an innovative approach to stormwater management that minimizes the environmental impact of urbanization. Stormwater is water that flows naturally through a watershed in the form of rain and snow-melt. The soil in farmlands and natural areas can absorb stormwater and slowly release it into rivers and streams, helping to create a constant, permanent flow of water. As the Nottawasaga Watershed becomes more urbanized, natural areas and farmland are replaced with hard surfaces such as parking lots, buildings and impervious surfaces.
LIDs mimics the natural processes that occur in farmlands and natural areas allowing rainwater and runoff to be absorbed into the ground. This approach helps ease the stresses that development puts on water resources, ecosystems, and overall environmental quality, including reducing pollution in our waterways and mitigating flood risk.
Why Use Low Impact Developments?
Natural areas and farmland are surprisingly efficient at handling large amounts of water. Water that is not immediately absorbed by plants is filtered through layers of soil and stone before becoming part of the groundwater system.
Stormwater and snowmelt cannot be absorbed by parking lots, roadways, sidewalks and buildings. Instead, this water stays on the surface and flows until it can be absorbed or collected. Sometimes, this causes floods that damage our homes and infrastructure, and can create dangerous situations for people.
Stormwater runoff can also collect and carry toxins and chemicals such as grease, oil, debris (plastics), and sediment. When this water flows into waterways, it pollutes lakes, rivers, streams and wetlands, which can harm and degrade the watershed and surrounding ecosystem. Using LIDs such as rain gardens, vegetated swales, and permeable pavements, pollutants can be filtered out before they reach water bodies. Additionally, LIDs can help to enhance the aesthetic and recreational value of developments. Features such as bioswales and rain gardens can provide habitat for wildlife, improve air quality, and create attractive green spaces for residents/homeowners to enjoy.
How Do LIDs Work?
LIDs are installed places where the water can make its way back into the ground at the place it falls, just like it would before an area was developed, mimicking its natural function. They are designed to allow water to infiltrated into the ground to reduce surface runoff, slow the speed of stormwater, as well as help recharge the groundwater.
Most LIDs work by directing stormwater to areas specially designed to be permeable, but some innovations are built around making our infrastructure itself more absorptive. By creating permeable surfaces that can allow stormwater to be absorbed into the ground below them instead of diverting it, less stress is put on the rest of the stormwater management system.
To make the ground more permeable, areas are filled with layers of stone and engineered soils that resist compaction, allowing water to flow into the water table below. Sometimes plants that have been specially chosen for their ability to absorb water or resist erosion are planted on the surface. These plants also help to collect sediment, debris, and even chemicals that get washed through them. These plants are called “riparian plants”, and we encourage developments to consult our approved landscaping list.
Types of Low Impact Developments
There are several ways LIDs can be implemented by developers and homeowners alike, many of which you’ve likely seen already. Below are just a few of LID techniques that can be used to reduce the effects of heavy rains and storm water events.
Rain Gardens
These low maintenance gardens collect stormwater runoff and allow it to drain into the natural soils below. Rain gardens are great additions to any property and help reduce the amount of stormwater that gets processed through storm drains. Rain Gardens are depressions of deep, loose soil that collect runoff from roofs, lawns, and other impervious surfaces. The surface is covered with hardy local plants with deep roots that thrive in moist conditions. Some rain gardens have a layer of crushed stone at the bottom to help with drainage. Because of their loose soil composition and specially chosen plants, rain gardens can absorb about 30% more water than a patch of grass the same size.
Rainwater Collection
Collecting rainwater is one of the easiest ways for people to start implementing their own low impact development. By disconnecting their downspouts from the municipal stormwater infrastructure and storing that water in a rain barrel or cistern, homeowners can reduce their impact on water management systems and save money. This is as simple as diverting your downspout into a large barrel or container. While the rainwater harvested from your roof is non-potable (not safe to consume), it can be used to give your gardens and lawn a drink or to wash your car. More advanced systems can also use this water to flush your toilets or to use in your laundry.
Bioswales
Bioswales are designed to slow runoff and help clean the water before returning it to a river or stormwater system. Like rain gardens, bioswales use loose, highly absorptive soil and water-hearty plants to help slow and filter flowing water. However, instead of creating a reservoir that fills and drains, bioswales allow the water to continue through and into a storm drain or other system, often using perforated drain pipes to help move the filtered water. Bioswales offer an aesthetically pleasing alternative to concrete gutters and are more effective than simple ditches at reducing the amount of pollution and sediment that makes it through them.
Permeable Pavement
Unlike asphalt and concrete pavements, permeable pavements allow parking lots, walkways, and many other traditionally impervious surfaces to let water through. Contaminants get filtered out as the water slowly drains through a gravel or engineered-soil base and into the native soil. These alternative pavements have been shown to reduce stormwater runoff and flooding, decrease pollutants in runoff, and replenish groundwater where installed. They’ve also been shown to reduce ice buildup on driving surfaces and hydroplaning accidents. Unfortunately, permeable pavers are not well-suited to areas that require snow clearing, as they are prone to damage from plows and clogging from sand.
LIDs and NVCA
One of the core functions of the Nottawasaga Valley Conservation Authority is flood risk mitigation. Part of reducing the potential of flooding and the damage it can do in our watershed is planning and enforcing low impact solutions for new developments in our region, and implementing our own LIDs wherever we can. By working closely and consulting with developers, municipalities, and the private landowners, NVCA can reduce the impact our growing urban areas have on our water quality and the ecology that relies on it.
For more information about Low Impact Developments, please contact NVCA’s Planning Department or visit our Planning and Permits page.
Who to Contact
Planning Team
705-424-1479 x 268
planning@nvca.on.ca
Stewardship Services
Recreation