Frequently Asked Questions


What is stormwater runoff?

Stormwater runoff is the rain or snowmelt that runs off streets, parking lots, lawns and other surfaces and drains into natural or manmade drainage systems. In town or subdivisions, the water drains into the storm drain conveyance system consisting of inlets and underground pipes. Did you know that in Anne Arundel County the storm drain system is separate from the sanitary sewer system (sinks, toilets, etc.). Sanitary sewer systems connect to wastewater treatment plants. Storm drains discharge directly to our streams, creeks, rivers and the Chesapeake Bay–untreated.

So, what’s the problem?

The problem is two-fold. The most obvious is the water quality impact. Untreated stormwater carries pollutants such as fertilizer from lawns, pesticides, oil and anti-freeze, pet waste, and sediment from construction sites. When this pollution enters our waterways, it causes algae blooms, a loss of fish and aquatic life, and public health issues such as beach closings.

The other problem is increased runoff and flooding. Imprevious surfaces including roofs, roads, parking lots, and other hard surfaces shed rain that was previously able to infiltrate into the soil. Traditional development transfers that water off-site as quickly as possible. Now, communities are realizing this rapid movement of water is causing downstream flooding and property damage; channel erosion and destabilization; and a loss of fishing and recreational opportunities.

How is stormwater a pressure on Anne Arundel County waterways and the Chesapeake Bay?

Stormwater runoff from land development of the Bay watershed is the only pollution source that is increasing!

Stormwater picks up nutrients, sediment and chemical contaminants as it flows across roads, yards, farms, golf courses, parking lots and construction sites. This polluted runoff travels into storm drains and local waterways that eventually drain into the Bay.

Development activities like clearing vegetation, mass grading, removing and compacting soil, and adding impervious surfaces have increased stormwater runoff in the Bay watershed.

  • Forest, wetlands and other naturally vegetated areas slow stormwater runoff and absorb water and pollutants. When these natural buffers are removed to make way for development, stormwater and the pollution it carries are able to flow freely into local waterways.
  • Impervious surfaces—roads, rooftops, parking lots and other hardened surfaces—do not allow precipitation to soak into the soil. Instead, water runs off and picks up dirt, trash, motor oil and other pollutants on its way to the nearest storm drain.
  • Muddy runoff from construction of new development contributes substantial amounts of sediment to the Bay and its tributaries.
  • Stormwater has eroded stream banks and damaged aquatic habitat in hundreds of miles of streams in the Bay watershed.
  • Stormwater runoff can also increase flooding in urban and suburban areas.


How much Bay pollution comes from stormwater?

Stormwater from urban and suburban areas contributes a significant amount of pollutants to the Bay. Every time we drive our cars, fertilize our lawns, leave pet waste on the ground or forget to fix car leaks, we contribute to pollution in our local rivers, streams and the Bay.

  • 17 percent of phosphorus, 11 percent of nitrogen and 9 percent of sediment loads to the Bay come from stormwater.
  • Chemical contaminants from runoff can rival or exceed the amount reaching local waterway from industries, federal facilities and wastewater treatment plants.


Where do excess nutrients come from?

Virtually all people and industries in the Bay’s seven-jurisdiction watershed — and even some beyond the watershed — contribute nutrients to the Bay and its tributaries. In general, excess nutrients reach the Bay from three major sources: specific, identifiable entry pipes; runoff from the land; and air pollution.

  • Wastewater treatment plants contribute the majority of nutrients that enter the Bay through specific, identifiable entry pipes. Wastewater plants release treated water — often still containing large amounts of nutrients — into local streams and rivers, which eventually flow to the Bay.
  • Nutrients that run off the land — including farmland and urban and suburban areas — come from a number of sources, including fertilizers, septic systems, boat discharges and farm animal manure.
  • Air pollution from vehicles, industries, gas-powered lawn tools and other emitting sources contribute nearly one-third of the total nitrogen load to the Chesapeake’s waterways. Airborne nitrogen is contributed to the Bay region from an enormous 570,000-square-mile airshed that stretches north to Canada, west to Ohio and south to South Carolina.

Nutrients also come from a number of natural sources, including soil, plant material, wild animal waste and the atmosphere.

Nutrients have always been a part of the Bay ecosystem, but not at the excessive levels found today. Prior to significant human activity in the region, most nutrients were absorbed or held in place by natural forest and wetland vegetation. As forests and wetlands were replaced by farms, cities and suburbs to accommodate a growing population, nutrient pollution to the Bay has vastly increased.


How are excess nutrients a pressure on the Bay?

Excess nutrients fuel the growth of dense algae blooms that:

  • Block sunlight that underwater bay grasses need to grow. Bay grasses provide food for waterfowl and shelter for blue crabs and juvenile fish.
  • Rob the water of oxygen, which crabs, oysters and other bottom-dwelling species need to survive.


How does sediment harm the Chesapeake Bay?

Excess sediment suspended in the water is one of the leading causes of the Chesapeake Bay’s poor health. The culprits are the tiny clay- and silt-sized fractions of sediment. Because of their small size, clay and silt particles often float throughout the water, rather than settling to the bottom, and can be carried long distances during rainstorms.

When there is too much sediment in the water, the water becomes cloudy and muddy-looking. Cloudy water does not allow sunlight to filter through to bay grasses growing at the bottom of the Bay’s shallows. Just like plants on earth, bay grasses need sunlight to grow; without it, these underwater grasses die, which affects the young fish and blue crabs that depend on bay grasses for shelter.

Large amounts of sediment can have other harmful effects on the Chesapeake Bay and the people who use it:

  • Nutrients and chemical contaminants can bind with sediments, allowing the pollutants to spread throughout the Bay and its local waterways. Fish and shellfish that live and feed near contaminated bottom sediments can themselves end up contaminated, triggering fish consumption advisories in various rivers and portions of the Bay.
  • Oysters and other bottom-dwelling species can be smothered when excess sediment settles to the bottom.
  • Excess sediment is the primary reason that many of the Bay watershed’s streams are degraded.
  • Ports and channels can become clogged by accumulated sediment, affecting commercial shipping and recreational boating.


Where does sediment come from?

More than 18.7 billion pounds of sediment are believed to enter the Chesapeake Bay each year. There are two major sources of this sediment: watershed sources and tidal sources.

Erosion of the land and stream banks are watershed sources of sediment. Watershed erosion increases when land is cleared of vegetation for agriculture and development. Scientists estimate that the majority of the sediment that flows to the Chesapeake Bay comes from watershed sources.

Erosion of shorelines and nearshore areas, as well as the resuspension of previously eroded sediments, are tidal sources of sediment. Tidal erosion increases when shoreline vegetation is removed and there are not enough bay grasses growing in the shallows to soften wave action against the shoreline.


What can I do to reduce the amount of stormwater pollution I contribute?

The cumulative impacts of each rain event on each parcel of developed property are dramatic. Before extensive development, the landscape absorbs much of the rainfall. This natural process filters out pollutants, recharges groundwater, and reduces the likelihood of erosion and flooding. In urban and suburban settings, rainfall washes over impervious surfaces, like rooftops and pavement, creating runoff. Downspouts, hard surfaces, and storm drains are used to divert and channel stormwater runoff, ultimately, directly into local waterways and the Chesapeake Bay. Rainfall that washes over impervious surfaces picks up a wide range of pollutants including fertilizers, pesticides, oils, metals, litter, pet waste, and sediment, which flow—unfiltered—to our waterways. This polluted runoff contributes greatly to the resulting dead zones in the Chesapeake Bay, which now includes more than a third of the bay each summer.

  • If you own a yard, don’t over fertilize your grass; and preferably don’t use commercial fertilizers—grasscycle instead by leaving grass clippings on the lawn. Never apply fertilizers or pesticides before a heavy rain. If fertilizer falls onto driveways or sidewalks, sweep it up instead of hosing it away. Compost leaves and grass clippings. Alternatively, bag leaves and grass clippings and place at the curb for collection—not loose in the street. Doing this keeps leaves out of the gutter, where they can wash into the nearest storm drain. Plant and stabilize bare spots to prevent erosion. Redirect downspouts to planting beds and practice rainscaping.
  • If you own a car, maintain it so it does not leak oil or other fluids. Be sure to wash it on the grass or at a car wash so the dirt and soap do not flow down the driveway and into the nearest storm drain.
  • If you have a septic system, maintain it properly by having it pumped every three to five years. If it is an older system, be sure it can still handle the volume placed on it today. Never put chemicals down septic systems, they can harm the system and seep into the groundwater.
  • Pet owners should pick up after their pets and dispose of pet waste in the garbage or toilet.
  • Keep lawn and household chemicals tightly sealed and in a place where rain cannot reach them. Dispose of old or unwanted chemicals at household hazardous waste collections sites or events.
  • Never put anything in a storm drain.
  • Don’t litter.

What can I do to reduce the volume of stormwater runoff?

Practice RainScaping . . . “Beautiful Solutions to Water Pollution!” The Chesapeake Bay and its tributaries won’t be restored to health until private property owners, who own 64 percent of the land in Anne Arundel County, begin implementing rainscaping practices to reduce the effects of polluted runoff. We can restore our waterways by practicing preventative measures such as properly disposing of litter, pet waste, and motor oil; and by reducing or eliminating the use of fertilizers and pesticides. Even more dramatic improvements are achieved if we also redirect downspouts to planting beds, install rain gardens and rain barrels, plant native trees and shrubs, and replace hard surfaces with permeable surfaces. By infiltrating and filtering stormwater runoff, the cumulative impacts of rainscaping will help restore our waterways, restore habitat, and add beauty to the landscape. Additional significant benefits are increased property values and a reduction in a community’s carbon footprint. It’s a win-win for you and the environment!

Aren’t rain gardens and other rainscaping practices difficult to install?

Not really. Usually simple enough to design and install without specialized technical expertise, rain gardens are simply low-lying, vegetated depressions—generally 3 to 6 inches deep—which have absorbent soils that “temporarily” collect stormwater runoff from impervious surfaces and allow the runoff to slowly percolate into the soil—usually within a few hours to 48 hours. Rain gardens have well-drained soil and are planted with moisture-loving native perennials, shrubs, and trees, to absorb and filter nutrients and pollutants from rainwater runoff and provide important habitat for pollinators and birds.

A simple rain garden is not a pond or a wetland; and it should not be confused with a complex “bioretention installation.” Although a rain garden is a type of bioretention planting arrangement, a bioretention installation generally refers to an installation that is more sophisticated than a rain garden, and is designed/engineered by a landscape architect or an engineer. Complex bioretention installations are designed to mitigate larger amounts of runoff. They are typically deeper than rain gardens and often incorporate underdrains.

Rain Gardens Across Maryland is an excellent guide to rain garden installation and other rainscaping practicess. It can be downloaded here (14 MB pdf).

Do rain gardens breed mosquitoes?

Mosquitoes lay eggs in standing water. Rain gardens do not hold rainwater long enough for mosquitoes to reproduce successfully.

According to Dr. David N. Gaines, Public Health Entomologist, Virginia Department of Health: “Most mosquito species can complete their life cycle in a flood pool or puddle that is present for more than 2 weeks, but will not be able to survive in a puddle that dries up after only one week.”

“Any temporary body of water that is present for more than a week can be a mosquito breeding habitat. Flooded cattle hoof prints in a muddy field have been known to produce dozens of mosquitoes each. The limiting factors are the longevity of the aquatic habitat, and the duration of the mosquito species’ life cycle (life cycle = time from egg hatch to emergence of adult mosquitoes from the water). The shortest life cycle on record for a mosquito is about 4.5 days, and this particular species breeds in mid-summer in the sun-warmed puddles of flooded fields, or areas of forest clear-cut (e.g., wheel ruts). It can only develop this quickly when the water conditions (i.e., temperature and food supply) are ideal. Other mosquito species typically have life cycles that take at least one or two weeks. Thus, most mosquito species can complete their life cycle in a flood pool or puddle that is present for more than 2 weeks, but will not be able to survive in a puddle that dries up after only one week.” -Dr. David N. Gaines

To read the full article “Mosquito Breeding Habitats,” by Dr. David N. Gaines, click here.

What if my rain garden doesn’t work exactly as planned?

Don’t stress too much over it. The rain garden does not have to be perfect to do its job, and it will change over time-that’s one of the things that makes it so rewarding: it’s a living, dynamic system. Dig a hole, relax, and let nature take its course. Observe and have fun. —Spencer Rowe, Wetland Scientist

Installing a rain garden incorporates both science and art. Your rain garden may or may not work perfectly right after installation is completed. Fret not, it’s often part of the process to make adjustments over time as needed, based on your site conditions.

For example, if you are mitigating a large area of impervious surface runoff with a rain garden, it may be helpful to channel the water so that it travels across a stone bed—which may need adjusting—before it reaches the plants. The stone bed can help slow the water so that it doesn’t wash away the first plants as it reaches the garden. Also, if your rain garden receives too much runoff, you may need to channel excess runoff to additional planting beds.

Part of the joy of gardening is working in harmony with nature and fine-tuning over time. Learn to appreciate nature and tolerate some imperfection in the garden. The experienced gardener welcomes in their garden not only the laws of nature, but the play of contingency, too. The experienced gardener accepts that a garden is never truly finished; that though they may tame nature for a time, their mastery is temporary at best.

As Roger B. Swain tells us, “Nature writes, gardeners edit.” And H. E. Bates reminds us, “A garden should be in a constant state of fluid change, expansion, experiment, adventure; above all it should be an inquisitive, loving, but self-critical journey on the part of its owner.” Among other things, a garden is a form of self-expression that can give body to our wishes. Trial and error gardening will answer many garden questions. In the garden, the voice of experience—distilled, collective, and well worn—speaks volumes. An open, flexible approach to gardening makes it a much more enjoyable experience—one that can also help keep you mentally and physically flexible and in shape. Study and imitate nature’s ways and means. Enjoy your newly created rain garden filled with the sights and sounds of birds and butterflies attracted to your native plants.

Why use native plants?

Native plants are species that are indigenous to a specific region, for example, the Chesapeake Bay watershed. They are adapted to the local soil and climate. As people moved from the Old World to the Americas, they brought exotic plants, and frequently changed the landscapes to resemble those that they knew in Europe and elsewhere. The result of the tendency to try to reproduce plants and plant arrangements from other countries is that thousands of acres of turf grass and many alien invasive species have been introduced.

Native plant benefits include:

  • Best adapted to local conditions, for example, no need to use chemical fertilizers.
  • Water conservation, that is, once plants are established in the right place, no need for supplemental watering.
  • Reduced maintenance over the long run. While native plants are not maintenance-free, if they are placed in the landscape based on their preferred conditions, they require less care than non-native species.
  • Won’t harm natural areas, e.g., won’t become invasive.
  • High habitat value provides food, shelter, and nesting areas for wildlife.
  • Great variety of species for all conditions and create a “sense of place.”

An excellent native plant guide is made available by the US Fish and Wildlife Service: Native Plants for Wildlife Habitat and Conservation Landscaping, Chesapeake Bay Watershed. This color guide provides planting requirements and uses for 400 native plants. For the on-line version, click here.

Who can answer my plant and pest questions?

Ask the experts! The Home and Garden Information Center can answer your plant and pest questions. Click here.

Are there any incentive programs to assist residents with their rainscaping projects?

WPRP Credit Program
Eligible property owners in Anne Arundel County have the opportunity to reduce their Watershed Protection and Restoration Fee (WPRF) assessments by up to 50% for proactive and sustainable uses of stormwater runoff controls. The WPRF Credit Program Policy and Guidance document for Anne Arundel County was approved by the Maryland Department of Environment and provides the Department of Public Works the framework and procedures needed to administer the program. For questions about the WPRF Credit Program call 410-222-4240 ext. 3322.

Maryland’s $25 Tree Credit

How do I report a violation?

In Anne Arundel County, call the Critical Area Hotline to report tree clearing, sediment runoff, illegal building: 410-222-7777. Be sure to call before you cut vegetation in the Critical Area: 410-222-7441.

The Chesapeake Bay Safety and Environmental Hotline is a toll-free phone number for Maryland citizens to call to report a problem on the tidal portions of Maryland’s portion of the Chesapeake Bay as well as the Coastal Bays. One phone call will now direct citizens to the appropriate agency to make a report 24 hours a day, 7 days a week.

Call – 1-877-224-7229 – to report any of the following:

  • Boating accident or reckless activity
  • Fish kill or algal bloom
  • Floating debris that poses a hazard to navigation
  • Illegal fishing activity
  • Public sewer leak or overflow
  • Oil or hazardous material spill
  • Critical area or wetlands violation
  • Suspicious or unusual activity

“It’s the 911 for the Chesapeake Bay.”