Stormwater 101 - Part One

TITLE: Stormwater 101 – Part One

AUTHOR: RiverLink staff

SOURCE: RiverLink website (https://riverlink.org/reduce-rain-runoff)

PERMISSION to publish granted by RiverLink. We acknowledge RiverLink’s dedicated section of its website: https://riverlink.org/reduce-rain-runoff. You can also go to RiverLink’s homepage and click on Reduce Rain Runoff at the top. RiverLink’s year-long campaign to bring greater awareness to stormwater issues and solutions has been supported by The Community Foundation of Western North Carolina,The Duke Energy Foundation, The McClure Foundation, and Land of Sky Regional Council.

The sheer volume and velocity of rain runoff is the biggest threat today to the health of the French Broad Watershed. Untreated rainwater flows off hard surfaces (such as parking lots and roofs) and carries sediment, pollutants and bacteria with it, negatively impacting water quality.

As Western North Carolina continues to grow its population and economy, rain runoff is increasing, a dramatic impact which is only being heightened by climate change. We all have an economic interest in keeping our waterways clean and beautiful. Together, the eight counties of the French Broad Watershed (Transylvania, Henderson, Buncombe, Madison, Haywood, Yancey, Avery, and Mitchell) can reduce rain runoff and protect our rivers.

We Paved Paradise

Urbanization happens when more and more people move to an area, and what was once natural or rural land is transformed for residential, commercial, and transportation purposes. With this development comes more hard surfaces that prevent rainwater from soaking into the ground.

The urbanization that comes with growth will increase the negative impacts on water quality and flooding, unless we design and plan for areas where rainwater can soak in, rather than simply heading for the storm drains — and the nearest stream.

Nature’s Filter

In urban areas, a whopping 55% of rainfall becomes runoff. Urban runoff picks up pollutants as it flows across hard surfaces before emptying into a nearby stream. This large amount of fast-moving water creates erosion, sedimentation, and flash flooding. Compare this to undeveloped areas where about 10% of rainfall runs off the landscape and the rest either soaks into the ground or evaporates. Urban planners, engineers, landscape architects, and property owners play a role in managing rainwater in a more natural way that protects our urban streams and communities from the harmful impacts of runoff.

Death by 1,000 Cuts: Urban Stream Syndrome

A single urban stream can have dozens, even hundreds of stormwater pipes emptying into them, each one delivering large amounts of fast-moving runoff during a storm. The common effects of runoff on these streams is called “Urban Stream Syndrome” and include:

·      “Flashy” water levels that rise quickly with even modest amounts of rain

·      High levels of pollutants

·      Unstable stream banks that erode easily

·      Fewer species of aquatic animals.

The cure for this syndrome is to reduce the amount of stormwater entering our streams through the use of green infrastructure. Healthy streams also need native woody plants growing on their banks to hold the soil in place and serve as a buffer that filters overland runoff before it reaches the stream.