What is Stormwater Runoff?

Stormwater runoff occurs when water from rain or snowmelt flows over the ground. Impervious surfaces such as driveways, sidewalks and streets prevent stormwater from naturally soaking into the ground.

Development typically replaces the natural landscape with impervious surfaces like roads, roofs and parking lots. When stormwater cannot sink into the ground, it has nowhere to go but to flow across the surface of the ground.

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1. What is Stormwater Runoff?
2. Why is does it matter?
3. What is Municipal Separate Storm Sewer System (MS4)?