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Maryland State Government Maryland Department of the Environment

Stormwater Management and the Chesapeake Bay

As land development increases the amount of such impervious surfaces as roads and parking lots in an area, the stormwater runoff from that area increases as well. This increase in runoff decreases the amount of rainfall that seeps into the ground, and increases the flow of water into the nearby streams, causing local flooding and stream channel erosion. Water quality is affected by the accumulation of trash, oil and rubber from cars, fertilizers and pesticides applied to lawns, sediment from bare or poorly vegetated ground, and other pollutants entering streams, rivers and the Chesapeake Bay. Inflow of sediment can cloud water, blocking sunlight from submerged plants. Sediment also settles to the bottom of streams, clogging the gravel beds used by fish for laying their eggs. Nutrients, such as phosphorous and nitrogen, from fertilizers enter the water and promote unusually rapid algae growth. As the algae dies, its decomposition reduces or eliminates oxygen needed by fish, shellfish, and other aquatic life for survival.

These are all examples of nonpoint source pollution, one of the major contributors to the degradation of Maryland’s waterways. Stormwater management controls nonpoint source pollution through the use of structural and nonstructural best management practices (BMPs) to intercept runoff from developed areas, filtering and treating stormwater runoff, and then discharging it at a controlled rate into the streams, rivers, and the Chesapeake Bay. The following BMPs are examples of stormwater management techniques that may be found in your community.

The Wet Basin is one of the primary tools for stormwater management. Wet basins are one of the most reliable and attractive BMPs and offer many environmental benefits, including habitat for waterfowl, wildlife, and warm-water fish. Through the temporary storage of stormwater runoff within the wet basin, followed by the gradual release of the excess water the wet basin allows time for sediment and other pollutants to settle to the bottom of the basin, enhancing the quality of the discharged water.

Shallow Marsh Basins are shallow pools that create growing conditions suitable for the growth of marsh vegetation. As the marsh plants grow, they act as filters removing nitrogen and phosphorous from the stormwater runoff. Shallow marshes also increase wildlife habitat in the urban environment, providing cover and food for an abundance of wildlife.

Filtering BMPs such as Infiltration Trenches, Sand Filters, and Bioretention Basins are devices used primarily for water quality management. In these BMPs, water is temporarily stored in a shallow trench or basin, and gradually seeps into the surrounding soil or filtering medium, removing pollutants and recharging groundwater. Trees, shrubs and grasses may be included in the design of filtering BMPs to enhance the water quality treatment and provide shade and wildlife habitat. As plants grow, they “drink” water from the surrounding soil, removing pollutants as they do so. Low growing plants act as a filter for runoff when their foliage is dense and close to the ground. Also, the roots of trees and plants enhance the seepage of water into the ground, recharging the groundwater.

Stormwater Management in Your Backyard

Successful stormwater management is achieved by controlling the quantity and quality of runoff from your property. The overriding condition, which governs stormwater runoff quantity, is the amount of hard, impervious surface located on your property (driveways, sidewalks, roofs, carports, etc.) Reduce these hard, impenetrable surface areas and you can reduce problems associated with excess stormwater runoff. Stormwater quality, however, is governed by the accumulation of pollutants on the entire surface area of your property, regardless of whether it is grassed or paved.

The greater your use of chemicals around the home such as fertilizers, pesticides, engine oils, deicing materials, etc., the more degraded the stormwater runoff from your property will be. Although your effect on stormwater quantity and quality may seem inconsequential, the cumulative impact of runoff from hundreds of thousands of yards across the State has been destructive to Maryland’s streams, rivers, and the Chesapeake Bay. Below you will find numerous tips for reducing the quantity and improving the quality of runoff from your backyard.

These Activities Will Minimize Stormwater Runoff from Your Property

  • Limit the amount of impervious surfaces in your landscape. Instead, use permeable paving surfaces such as wood decks, bricks, and concrete lattice to allow for water to soak into the ground.
  • Allow “thick” vegetation or “buffer strips” to grow alongside waterways to slow runoff and soak up pollutants.
  • Plant trees, shrubs, and groundcover. They will absorb up to fourteen times more rainwater than a grass lawn and they don’t require fertilizer. For more information on tree planting, call the Maryland Department of the Natural Resources at (410) 260- 8DNR or visit their Web Page (www.dnr.state.md.us).

These Activities Will Reduce Fertilizer, Pesticide, and Sediment Runoff

  • Use natural alternatives to chemical fertilizers and pesticides. If you must use them, test your soil to determine the appropriate amount. For more information call the Maryland Cooperative Extension Service at 1-800-342-2507 0r visit their website at www.agnr.umd/users/hgil/
  • If a lawn care company services your lawn, make certain it is not applying “blanket” applications of fertilizer and pesticides. Ask if they have conducted soil tests and a pest analysis to determine appropriate applications.
  • Resod or reseed bare patches in your lawn as soon as possible to avoid erosion.

For more information on nonpoint source pollution and stormwater management, please call the Maryland Department of the Environment, Water Management Administration at (410) 537-3000.

Related Topics

Model Stormwater Management Ordinance (pdf)
Public Notice on Tentative Determination to Issue General Discharge Permit No. 03-IM-5500