What Exactly is Stormwater Runoff?
Exactly what it sounds like! It’s when water (or snow) from storms “runs” or flows over the ground. Under natural conditions, such as a grassy meadow, this precipitation doesn’t flow very far because the ground is able to soak it up. However, problems arise in locations that have lots of hardened surfaces, like concrete, that prevent the water from being absorbed into the ground.
Our man-made system of pavement, gutters, and storm drains quickly carries stormwater runoff directly into local streams, rivers, and the Chesapeake Bay—without any natural filtering process. That means any debris, chemicals, dirt, and other pollutants in that water are flowing untreated into the waterbodies that we use for swimming, fishing, and drinking water.
Some studies show that about 50 percent of such pollution comes from individuals and homeowners through yard maintenance and chemical pollution from household activities.
The good news is there are various techniques we can use to lessen the impact of stormwater, especially when it is next to the source, such as a driveway or roof, such as installing rain gardens, rain barrels, green roofs, and pervious pavers. These solutions mimic natural conditions by capturing the stormwater runoff and slowing it down so it can slowly drain into the surrounding environment instead of washing straight into our rivers. Nutrients, such as nitrogen and phosphorus, which would otherwise contribute to algae blooms and other problems in the Bay, are instead put to beneficial use by being taken up by the plants in the garden. Additionally, the absorbed water increases groundwater supply, which is important because many people get their water from underground aquifers.
You can do your part to stop polluted stormwater from entering our Rivers and Bay by installing a rain garden. Different from a common flower garden, a rain garden is created by making depressions in the landscape to collect the stormwater and allow it to slowly infiltrate into the ground, as nature intended. Planting native plants, trees, and shrubs in a rain garden will also help absorb some of the stormwater. This design allows for the rain garden to capture large amounts of precipitation and slowly drain it within a few short days of rainfall. Native plant rain gardens also become attractive landscaping features- wildlife oases with colors, fragrances, sights and sounds with the added benefit of songbirds and butterflies regularly visiting.
Download design and installation instructions, sample rain garden designs, and plant lists from Chesapeake Ecology Center below.
This can be a common source of confusion and the words are often used interchangeably. Both designs slow down water and use plants to uptake pollutants. In general, rain gardens are smaller and don’t require heavy machinery to install. Bioretention projects tend to be much larger and can have many levels of sand, mulch, and rock under the plants to better filter out pollutants.