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Watershed
Restoration
THE CLEAN WATER BOOK:
CHOICES FOR WATERSHED PROTECTION
     
CHAPTER 3:
MANAGING THE FLOW OF STORMWATER
 

Stormwater runoff is the most common way that nonpoint source pollution reaches local rivers, creeks and lakes. Stormwater can carry chemicals, nutrients, sediments, debris and other forms of NPS into local streams (either directly or through storm sewers) if the water is not absorbed by soil and vegetation.

In addition to preventing stormwater contamination from nonpoint source pollutants, one of the major goals of stormwater management is to increase the absorption of stormwater by soil and vegetation. This is usually done by reducing the speed of stormwater flow and allowing it to infiltrate into the ground. This will also reduce the amount of pollutants being carried off into storm sewers and streams and reduce flooding. Increasing stormwater absorption by soil has added benefit of helping to maintain ground water supplies, which are seriously depleted in many areas.

Stormwater should be viewed as a valuable resource that recharges our ground water supplies rather than as a nuisance to be quickly channeled away and lost to the ocean. In the past, stormwater management was primarily concerned with flood reduction. The goal was to quickly eliminate stormwater from the watershed and send it downstream. One of the consequences was the lack of ground water recharge.

Ground water recharge provides the base flow for streams during dry weather and also infiltrates into our aquifers, which provide drinking water through wells for about half of the state's population. Reduced ground water recharge is felt most severely during droughts when streams and wells run dry.

Today's stormwater management program also takes into account stormwater quality as well as quantity. The goal is no longer to flush stormwater downstream and eliminate it. Preventing stormwater pollution, recharging ground water and maintaining stream ecology are all part of the new stormwater management philosophy.

 

STORMWATER MANAGEMENT BASICS

Stormwater flows into the stormwater system through a storm drain. These are frequently located along the curbs of parking lots and roadways. The area beneath the grate that prevents larger objects from flowing into the storm sewer system is called a catch basin. Once stormwater enters the catch basin, it flows through pipes, which lead to an outfall where the stormwater enters a stream, river, lake or the ocean.

In some areas of the state, the outfall may lead to a stormwater management basin, rather than to a surface water body. The basin controls the flow of stormwater and can also improve water quality, depending on how they are designed. Some of these basins discharge to local waterways while other retain the stormwater and allow it to infiltrate into the ground.

In some older urban areas of the state, the stormwater and sanitary sewer systems may be combined. Here both stormwater and sewage from households and businesses travel together in the same pipes. Both stormwater and sewage are treated at sewage treatment plants except during heavy rains. During these occasions, both the stormwater and untreated sewage exceed the capacity of the treatment plant and this untreated combined sewer overflow is directed into local waterways.

 

THE IMPACTS OF URBANIZATION

Urbanization (or development) has a great impact on local water resources. With the increase in impervious surfaces (roads, rooftops, parking lots and other hard surfaces that do not allow stormwater to soak into the ground), the rate of stormwater runoff is increased. This means a greater volume of water reaches the waterway faster and less of that water is able to infiltrate into the ground. An increase of impervious surfaces can also result in an increase in flooding after storms and a reduction of flow during dry periods. The reduced amount of infiltrating water can lower ground water levels, which in turn can stress downstream environments, which depend on steadier flows of water.

In the stream, more erosion of stream banks and scouring of channels will occur. This in turn degrades habitat for plant and animal life that depend on clear water. Sediment in water clogs the gills of fish and blocks light needed for plants. The sediment settles to fill in stream channels, lakes and reservoirs.

In addition to the high flows caused by urbanization, the increased runoff also contains contaminants. These include litter, cigarette butts and other debris from sidewalks, motor oil poured into storm sewers, settled air pollutants from car exhaust as well as pesticides and fertilizers from lawn care. These contaminants reach local waterways quickly after a storm.

 

PROTECTING STORMWATER COLLECTION SYSTEMS

In the first rush of water from a rainstorm, much of the debris and other polluting substances that settled on the land surface and in the stormwater collection system since the last storm will be picked up and carried into the local surface water body. This can significantly add to water quality problems. Therefore, it is important to protect all components of the stormwater collection system from sources of pollution. The following should never be dumped down storm drains or catch basins, or on the street: motor oil, pet waste, grass trimmings, leaves, debris and hazardous chemicals of any kind. Anything dumped in our stormwater collection systems can be carried into our streams.

Keeping catch basins clean and free of debris is one way to protect stormwater quality. Pick up debris along the street that will otherwise be washed into the basins with the next storm. Avoid raking leaves into the street where they could wash into and clog the catch basins.

Participate in a local storm drain labeling project to educate others that what goes into the catch basins will be carried to our local rivers and streams. Many catch basins have been labeled with stencils or markers that indicate that its stormwater flows to a local waterway. Educate your neighbors and community about what should and should not go down the storm drain.

If there is a stormwater management system in your community, find out who is responsible for maintaining it. It may be an individual, a homeowner's association or a government agency. Check with your municipality to see who owns the property. If you see problems such as large amounts of debris or damaged structures, be sure to contact the responsible party.

 

REDUCING RUNOFF

There are inexpensive ways to control excess runoff created by patios, driveways, sidewalks and roofs around your own home. Regardless of the soil drainage condition in your neighborhood, landscaping and careful grading of your property can be used to control runoff, reduce its velocity and increase infiltration. Just like reducing nonpoint source pollution, many small stormwater management control measures can lead to a large difference in stormwater flow.

For example, land immediately adjacent to your house needs to have a downhill slope so that water does not seep through the foundation. Once the water has been carried approximately ten feet from the house, the surface should be graded so that runoff is released gradually. Surface runoff can be decreased and ground water infiltration increased by the following suggestions:

  • Plant trees or shrubs to promote filtration.
  • Install gravel trenches along driveways or patios to collect stormwater and filter it into the soil.
  • Connect downspouts carrying the roof runoff into "dry wells" for recharging the ground water.
  • Install rain barrels under the downspouts to capture the rainwater for later use in your gardens.
  • Re sod bare patches in your lawn as soon as possible to avoid erosion.
  • Grade all areas away from your house at a gentle slope of at least 1%.
  • Use a grass swale (a man-made low area in the lawn) to move water from one area to another.
  • Consider installing a rain garden to promote infiltration.

If you are building a new home or are considering regarding your property, you may want to create a basin which will hold all runoff and allow it to infiltrate into the soil over a longer period of time. This should be done only where drainage is good. Alternatively, you may be able to create a gently rolling surface or a system of berms, or mounds, and swales to slow runoff. Berms and swales are slight elevations and depressions in the surface that provide channels along which water will flow. If you have a wet area, you may be able to move the basin to a less used area of the yard - around shrubs or trees, for example - by installing a swale to carry the water across the yard. Plant trees and shrubs that thrive in wet soils in the new wet area. Be advised that most activities performed in regulated wetlands require a permit. Contact the NJDEP Division of Land Use Regulation for information at (609) 292-0060.

 

RAIN GARDENS

Rain gardens are a small-scale method of allowing runoff to recharge our ground water. A rain garden is simply a low-lying garden that captures rain water, allowing it to soak naturally into the soil. It can help address a wet area in your lawn while providing a pleasing landscape feature. Rain gardens can filter and reduce pollutants in runoff such as nutrients from lawns and oils from roadways.

 

REDUCE IMPERVIOUS SURFACES

One method of reducing stormwater runoff is to minimize the amount of impervious surfaces such as concrete sidewalks and asphalt driveways. These surfaces do not allow runoff to seep into the ground. A paving surface that allows water so soak in may seem impossible, but there are many materials that provide the durability of concrete while allowing rain water to filter into the ground.

If you are planning a new patio, walkway or driveway, there are several attractive alternatives to impervious concrete. Here are some examples.

  • Wood or recycled plastic decks, usually installed for their functional good looks, can serve as a form of porous pavement. Decking allows rain water to soak into the ground beneath it, and the space between the planks provides ample room for precipitation to drain directly onto the soil surface. As long as minimal air space is maintained between the soil surface and the decking, wood rot can be minimized.
  • Bricks, interlocking pavers or flat stones (flagstone, bluestone or granite) can be used to construct an attractive, durable walkway. If placed on well-drained soil or on a sand or gravel bed, these modular pavers allow stormwater infiltration. Avoid using chemicals to control weeds growing in the joints between the pavers; Corsican mint or moss can crowd out weeds and add beauty to the paved area.

These kinds of porous paving materials can be used wherever natural soil drainage is adequate and there are no problems with either bedrock near the surface or seasonal high water table.

 

LANDSCAPING STRATEGIES

Planting trees and other vegetation is one way to protect land and local streams from the damage caused by excessive runoff and erosion. Trees have long been appreciated for their beauty, but their help in minimizing erosion is not as well known. Landscaping by planting shrubs, trees and ground covers has definite environmental benefits, and enhances the appearance and value of property. Realtors suggest that mature trees and landscaping increase the value of homes as well as the speed of sale.

Trees and other plants reduce the flow of stormwater by absorbing the water and providing a rougher surface to slow the water. For example, water flows more slowly through shrubs, leaf litter and mulch that it would over an asphalt driveway just because of the difference in surface texture.

Trees and other plants can create "outdoor rooms" where you and your family can work and play. Well-planned landscaping can reduce heating and cooling costs for your house by as much as 30%. New native shrubs and trees may attract birds and wildlife. Trees, shrubs and ground cover also require less maintenance than grass. Because trees and shrubs require less fertilizer and fewer herbicides than grass, the chances of polluting streams is minimized.

Landscaping your yard with stormwater in mind can help to reduce the erosive force of stormwater runoff and increases the value of your home. By planting trees, shrubs and ground cover, you encourage excess rain water to filter slowly into the soil instead of flowing directly into storm drains or local surface water bodies. Choosing trees and plants that are appropriate for your soil and growing conditions will ensure that you will have a beautiful yard.

For more information on landscaping, read the chapter on Lawn and Garden Care.

 

LANDSCAPING FOR WILDLIFE

Another possibility is landscaping for wildlife. By selecting appropriate plants, landscaping can reduce water pollution and serve wildlife too. Four basic elements will need to be provided for wildlife: food, water, shelter and space. Food can be supplied through vegetation that provides seeds, nuts or berries. Water, if not available nearby as a stream or lake, can be provided as a small pool or pond. Shelter which provides protection from predators or the weather can be vegetation, a pond or even a brush pile. Space needs vary among wildlife but include enough room to reproduce, find food and carry on the different parts of their life cycle. The specifics depend on whether or not you are trying to attract a variety of wildlife or certain group, such as butterflies or hummingbirds. For more information, contact the NJDEP Division of Fish and Wildlife, PO Box 400, Trenton, NJ 08625-0400

 

WHAT YOU CAN DO

By following these few simple guidelines, you can make your home more attractive and help prevent erosion.

  • Never dump motor oil, grass trimmings, leaves, animal waste or other pollutants into the street, storm drains or catch basins.
  • Landscape your yard to minimize stormwater runoff.
  • Limit impervious surfaces in your yard.
  • Divert rain from paved surfaces onto grass or other vegetated areas to permit infiltration.
  • Choose the appropriate plants, shrubs and trees for the soil in your yard. Consult you local nursery or Rutgers Cooperative Extension for advice on which plants, shrubs and trees will require less water, fertilizers and pesticides.
  • Help to keep your local catch basins clean and functioning by picking up debris along the street that will otherwise be washed into the basins with the next storm. Avoid raking leaves into the street where they could wash into and clog the catch basins.
  • Participate in a local storm drain labeling project to educate others that what goes into the catch basins will be carried to our local rivers and streams.
  • If you live near a catch basin or stormwater management basin, see that it is being properly maintained.
 
continue to Chapter 4: Protecting Shorelines
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Last Updated: June 8, 2012