News & Events

Stormwater Management in the Town of Bridgewater

  • Storm drain collecting runoff in the Town of Bridgewater, Nova Scotia

 

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.

 

urban runoff

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

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

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 Bluenose 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.