Impermeable Surfaces

Seventy percent of Toronto is impermeable. Impermeable surfaces such as roads, sidewalks, driveways and buildings don’t allow water to pass through them so it can’t infiltrate into the soil. Instead water flows quickly over these surfaces as runoff.

permeable surfaces 

When water flows as runoff, it picks up oil, salt, dog poop, pesticides and a host of other pollutants. Although runoff can occur even in highly permeable areas during high volume rain events, runoff in areas with low permeability generally occurs with increased speed, heat, and toxicity.

Most of the pollutants that reach our river arrive through runoff. Understanding how the path of stormwater is influenced by impermeable surfaces is another key step to solving the problem of river pollution. The next step is finding out what these pollutants are and pinpointing their origins. Once we find out what we are doing to pollute, we can change our habits and work towards cleaning Toronto’s watersheds!

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