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Fallen tree over creek

Stormwater can be generally defined as the runoff of rain or snowmelt from a site that is not absorbed into the ground. This runoff comes from the impervious or hard surfaces such as roofs, driveways, streets and parking areas. It is captured through storm drains, pipes, creeks and basins, where it is released over time to mimic the release prior to development. Runoff can pick up pollutants as it travels to the storm systems, such as lawn fertilizers, oils from cars, pet waste, eroded soils and any trash. Storm water is not treated so it is important to all of us that we try and keep these waters as clean as possible. Wherever you live or work, you are in a watershed and we need to keep our watersheds healthy for today and into the future.

What is stormwater runoff?
Runoff is the rain or snowmelt that flows off a property rather than being absorbed into the ground. This runoff is the result from the addition of driveways, parking lots, a building roof or any other impervious surface.

Storm runoff explanation graphic

What is an impervious surface?
An impervious surface does not let water become absorbed into the ground like it did before the property was developed. The original grassy or wooded property that absorbed the water is replaced with different surfaces that act as a barrier to absorption. These surfaces can be buildings, driveways, streets, sidewalks or parking lots. As the impervious surface generates greater runoff than the natural property, this additional runoff requires some type of storage to limit the impacts downstream. Most subdivisions have a required stormwater basin for this reason.

Storm runoff explanation graphic
(Click for larger image)

Why is it important to manage stormwater runoff?
Stormwater picks up pollutants as it travels to the storm system and creeks. There is no treatment to remove these pollutants, so it is important to keep the waters clean. Most public water supply systems are downstream of urban runoff areas. Types of pollutants can include fertilizers, car wash soaps and oils, as well as pet waste.
Stormwater pollutants
(Click for larger image)

Who owns the stormwater system in Rochester Hills?
The inlet grates that take direct road runoff are owned by the City of Rochester Hills as they are an integrated part of the city owned street. The individual sump line discharge for any single lot is owned by that property owner. All other common collection storm system pipes, structures and storage basins are owned by the benefiting development. While some communities own storm pipes in the rights of way, Rochester Hills does not currently have this same ownership. When Rochester Hills was a township, it was quite common to not include right-of-way pipes as public ownership. This concept carried forward when we became a city in 1984, so ownership continued on as before.

Links for reference
Detention Basin Manual
Frequently Asked Questions

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