Introduction

Stormwater is precipitation that runs off into waterways rather than soaking into the ground. In urban environments, it flows from rooftops and over streets, parking lots, bare soil, and sloped lawns. Stormwater runs directly into the Bow River from the towns of Banff, Canmore, Cochrane, and especially the City of Calgary - runoff from the latter exceeds the total runoff from all other communities. As well, stormwater from the towns of High River, Okotoks, Black Diamond, and Turner Valley drains into the Highwood and Sheep Rivers, which flow into the Bow River. The City of Airdrie drains into Nose Creek, which flows through Calgary into the Bow River.

FIGURE 2.01 Nose Creek flowing through subdivision development (Diana Faucher)

In the past, the major objective of urban stormwater drainage systems was to divert the stormwater away from streets and basements as quickly as possible and discharge it directly into local bodies of water. However, it has become clear that urban stormwater volume and quality have a major impact on the streams, rivers, and lakes into which it flows, necessitating new approaches to urban stormwater management.

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