What is stormwater? 
Stormwater is rain and melting snow that runs off rooftops, driveways, parking lots, roads, sidewalks and other hard surfaces.  As seen in the image below, a portion of the precipitation that we receive can either be evapotranspired, converted into surface runoff, stored in the soils or percolated into groundwater. When we convert a forested watershed into a paved and more urbanized landscape a much larger portion of the rainfall becomes surface runoff.  As the amount of impervious surfaces within the landscape increases it corresponds to both an increase in volume (i.e. amount) and speed (i.e. rate or flow) of runoff compared to the pre-developed land use condition.

The relationship between impervious cover and surface runoff. Image source: http://www.learnnc.org/lp/editions/mudcreek/6394.

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Stormwater impacts water quality and quantity

Traditionally, this surface runoff is conveyed directly into receiving water bodies (e.g., streams, rivers, lakes) through the stormwater infrastructure such as drains, pipes, culverts and other water carrying systems. The stormwater carries trash, bacteria, heavy metals and other pollutants from the landscape, degrading the quality of the receiving waters. Higher flows can also cause erosion and flooding in streams, damaging habitat, property and infrastructure.
Another concern is that many towns have “combined” storm sewers that also collect sanitary waste water – all this water is carried to the Waste Water Treatment plant for safe handling. However, due to the nature of combined sewers, storm events can result in untreated sewage waste overflowing into receiving waters.
In summary, stormwater impacts water quality and quantity by:

• transporting pollution (e.g., sediment, nutrients, debris, household hazardous wastes) directly or indirectly via storm sewer systems into rivers, lakes and streams;
• eroding shorelines, by increasing the volume and velocity of runoff entering receiving water bodies;
• flooding basements and/or on property;
• warming up surface water, making it more susceptible to waterborne bacteria and hazardous to fragile aquatic life;
• overflowing sewage treatment facilities, allowing untreated human waste to flow directly into receiving water bodies.

Implications of climate change
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Changes in the amounts and intensity of precipitation events associated with climate change along with aging infrastructure and an expanding area of impervious surfaces in most cities and/or towns in Nova Scotia and across Canada make managing stormwater a critical issue.
This is why the Coastal Action Foundation has partnered with the Town of Bridgewater to help them better manage stormwater.  So what can be done? Slow it, spread it, sink it.  Slow down the stormwater, spread it out into or over pervious surfaces (e.g., rain gardens) and sink it back into the ground. 

SLOW IT, SPREAD IT, SINK IT
Improving stormwater management on your property can help to improve drainage; lower risk of flooding, basement infiltration, and erosion; enhance the look; and improve the health of streams, rivers and lakes. Here are seven tips on how to better management stormwater on your property: ​

1. Increase green space
You can increase the amount of green space around your home by planting more vegetation such as native trees.  There are multiple ways that trees reduce stormwater. Tree reduce stormwater runoff by capturing and storing rainfall in the canopy and releasing water into the atmosphere through evapotranspiration. Tree roots and leaf litter create soil conditions that promote the infiltration of rainwater into the soil. This helps to replenish our groundwater supply and maintain streamflow during dry periods. Trees also helps to slow down and temporarily store runoff, which further promotes infiltration, and decreases flooding and erosion downstream.  As another bonus, trees also reduce pollutants by taking up nutrients and other pollutants from soils and water through their roots, and by transforming pollutants into less harmful substances.

2. Build a rain garden
Rain gardens are small, landscaped areas that capture, filter and infiltrate rainwater. Rain gardens can create an attractive detention area where runoff can slowly soak into the ground, be taken up by plants and return to the atmosphere through evapotranspiration. Rain gardens allow at least 30% more water to infiltrate into the ground compared to a conventional lawn.  

​To learn more about building a rain garden on your property, check out this guide: Rain Gardens

3. Install a rain barrel
Rain barrels, sometimes called cisterns, are aboveground water storage vessels.  They capture rain runoff from a building’s roof using the gutter and downspout system. Rain barrels with a drainage valve can store water for use between rain events. When the valve is opened, the water empties out slowly, thus reducing runoff and increasing infiltration.  Rain barrels help to divert water from storm drain systems and thus reduce pollutants and the velocity of water entering local rivers and streams; Store high quality water for gardens; direct overflow water away from building foundations to more desired locations; and reduce water and sewer bills, as well as electrical bills from sump pump usage.

4. Bioswale
Also known as "infiltration swales", "filter strips", or "grassed swales", bioswales are open vegetated channels specifically designed to attenuate and treat stormwater runoff for a defined water volume. Like open ditches, they convey larger stormwater volumes from a source to a discharge point, but unlike ditches, they intentionally promote slowing, cleansing and infiltration along the way. A sloped base to facilitate this water movement distinguishes bioswales from rain gardens. Because they behave like a gutter, these trenches are best suited along roadsides or parking lots. 

5.  Keep it clean
Stormwater picks up litter, sand, bacteria, oil,and other chemicals as it flows over the land, and it carries these pollutants to our water bodies. Runoff from paved surfaces, such as roads. parking lots, and rooftops, may contribute large amounts of polluted stormwater. Simply by putting fewer pollutants on the land, stormwater will been cleaner as it flows into our water bodies. Some tips include using a commercial car wash that treats and/or recycles the wash water, maintain your car to prevent fluid leaks, NEVER pour or sweep anything down a storm drain, and limit herbicide, pesticide and fertilizer use on lawns. 

6. Redirect or disconnect your downspout
Sometimes downspouts are connected to standpipe that moves water directly into the stormwater system, or the downspout empties water onto your lawn or paved surface. Downspout disconnection refers to the rerouting of rooftop drainage pipes to drain rainwater to vegetated areas of your property such as rain gardens or wet ponds or to specifically design collection areas (e.g., rain barrels, cisterns). Downspout disconnection stores stormwater for future use and/or allows stormwater to infiltrate into the soil, or evaporate. 

7. Replace and avoid hardscapes
Permeable pavement, also known as pervious or porous paving, is designed to allow percolation or infiltration of stormwater through the surface into the soil below where the water is naturally filtered and pollutants are removed or removed by a subsurface drain. Permeable pavement can be used instead of standard asphalt and concrete for surfacing sidewalks, driveways, parking areas, and many types of road surfaces. Standard asphalt and concrete are considered to be “impermeable.”

Stormwater Management Demonstration Sites in the Town of Bridgewater, Nova Scotia

Over the last two decades, the momentum for green stormwater infrastructure has been growing. The Coastal Action Foundation in partnership with the Town of Bridgewater want to encourage property owners to consider alternatives (i.e., rain garden, rain barrel) to traditional stormwater management infrastructure. The creation of stormwater management demonstration project sites on high traffic public property sites is intended to create highly visible projects that will inspire others to take action in order to reduce the volume and pollutant loading entering into receiving waterways.  The construction of these projects will provide hands-on training opportunities for both property owners and Town of Bridgewater staff.  
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Mariners' Landing Park, Town of Bridgewater, Nova Scotia

In August 2013, the Coastal Action Foundation partnered with the Ecology Action Centre to design and build a rain garden in Mariners' Landing Park which is located in the Town of Bridgewater, Nova Scotia.  Rain gardens are small, landscaped areas that are designed to capture, filter and infiltrate rainwater. Planted with water-tolerant native plants, rain gardens can become a beautiful and functional feature on your property.

The rain garden space with the sod, and soil removed. A rain garden should be relatively flat, as this is where the rain will slow down and settle and be absorbed into the ground over the next 24-48 hrs.

After the sod and soil were removed, the area was filled with 2-3 inches of gravel (to help with infiltration), landscaping fabric (to prevent mixture of soil and gravel), and nutrient-rich, organic top soil. Native, water-loving plants were then planted and the garden was mulched.