What is wet weather flow?
Wet weather flow — also known as stormwater pollution — is runoff that’s generated when it rains or snow. In a natural setting where there’s a lot of grass or vegetation it’s not usually a problem because the rain filters into the ground. But we live in a modern city where there’s a lot of concrete, asphalt, brick, and this changes the way water moves and what it picks up along the way to the sewer.
Wet weather flow — also known as stormwater pollution — is runoff that’s generated when it rains or snow. In a natural setting where there’s a lot of grass or vegetation it’s not usually a problem because the rain filters into the ground. But we live in a modern city where there’s a lot of concrete, asphalt, brick, and this changes the way water moves and what it picks up along the way to the sewer. That means that, in our city, a lot of stormwater runs off roofs, roads and parking lots. It trickles down drain pipes and empties into stormwater grates. Once it enters the grate (having collected dirt, oil, grease and a lot of other debris along the way), it then travels through our extensive storm sewer system – 4,500 km in all – to some 2,600 outfalls or outlet pipes. From there it enters our rivers, streams and Lake Ontario.
