Urban Home*A*Syst - What Is Runoff?

Runoff usually starts as rainwater that does not readily soak into the ground. This water flows from rooftops, over paved areas, on saturated or compacted soil and across sloped lawns. The flowing runoff collects and transports soil, pet waste, pesticides, fertilizer, oil and grease, leaves, litter and other potential pollutants. You don’t need a heavy rainstorm to send pollutants rushing toward streams. Your hose can supply enough water. Even if your home is not on a streambank, storm drains carry runoff from your neighborhood to the nearest body of water.

Contrary to popular belief, storm drains do not carry runoff to the wastewater treatment plant for treatment. Storm drains connect to pipes laid underground, often below streets. Inlets or drains located along curbs and in parking areas collect runoff, which then flows untreated to nearby streams, and from there to lakes such as Beaver Lake which is the drinking water source for much of Northwest Arkansas.

Completing this chapter’s self-assessments helps you find out how runoff affects the environmental quality of your property and properties “downstream” from your residence. This chapter also gives you tips on reducing stormwater runoff pollution risks.

Runoff in urban areas occurs much more quickly than runoff from either agricultural land or forested land. This means that pollutants are more likely to be transported from urban areas.

Polluted runoff can degrade our creeks, rivers and lakes. Soil clouds water and degrades the habitats of fish and water plants by filling in stream beds. It also makes the creek less attractive.

Nutrients such as nitrogen and phosphorus promote the growth of algae, which crowds out other aquatic life. Nutrients in runoff can be from overuse of fertilizers on lawns and gardens. It can also be from improper timing of fertilizer use. Many of our lawn care products are great on yards but cause problems if they get into nearby streams.

Toxic chemicals such as antifreeze and oil from leaking cars, carelessly applied pesticides and zinc from galvanized metal gutters and downspouts threaten the health of fish and other aquatic life.

Bacteria and parasites from pet waste and improperly managed septic systems can make nearby lakes and streams unsafe for wading and swimming after storms. There have been problems in the past with bacteria levels in Clear Creek, and several beaches at Beaver Lake have been temporarily closed due to high coliform levels.

Stormwater also can flow down a poorly sealed well shaft and contaminate drinking water (groundwater). These pollutants, often in minute concentrations such as parts per billion, are not detected by taste or odor, but can be a threat to human health.

Non-point source pollution such as runoff cannot be collected and treated centrally in the same way as pollution from point sources, such as wastewater treatment plants. Runoff pollution does not come from a few sources. Rather, runoff carries pollution from every street, parking lot, yard and garden. Solving the problem requires everyone’s help.

Runoff usually starts as rainwater that does not readily soak into the ground.

Take a few minutes to go through the following assessment to determine your risk of contribution to runoff pollution from your property. Then read about the areas where you have the highest risk to learn more about things you can do to reduce the potential for runoff pollution from your property.

Use the following chart to rate your runoff pollution risks. For each question, mark your risk-level in the column labeled “Your Risk.” Although some choices may not describe your situation exactly, choose the response that best fits.

	Low Risk Recommended	Medium Risk Potential Hazard	High Risk Unsafe Condition	Your Risk
Storage of pesticides, fertilizers and other potentially harmful chemicals	Stored in waterproof container in garage or shed out of reach of rainfall. Containers clearly labeled and out of the reach of children. Buy only what you need to reduce the need to store leftovers.	Stored in waterproof containers but within reach of rain water. Containers not clearly labeled. Buy chemicals based on price instead of actual needs.	Stored in non-water proof containers. Not clearly marked. Accessible to children. Storage area often wet.	High Medium Low
Handling and use of pesticides, fertilizers and outdoor chemicals	Keep absorbent material like cat litter on hand for spill clean-up. Apply only recommended amounts and control the watering-in of fertilizers immediately after application. Delay applications to avoid rain.	Don't delay applications to avoid rain. Sometimes increase the recommended rate based on my own judgment.	Don't clean up spills. Rinse equipment out on my driveway. Generally try to over apply to be sure the product is doing some good. Try to wait until right before a rain to fertilize.	High Medium Low
Car Washing	Cars and trucks taken to a commercial car wash or spray booth.	Vehicles washed on lawn instead of driveway.	Vehicles washed on driveway.	High Medium Low
Automotive wastes	Always clean up oil spills with absorbent material. Take used oil to collection center. Store anti-freeze in a safe place.	Don't clean up oil spills. Anti-freeze stored in areas accessible to children or pets.	Wash oil spills of the driveway and into the street. Pour old gasoline down the storm drain. Apply used motor oil as a lawn edger.	High Medium Low
Pet and animal wastes	Bury poet waste away from garden, ditch or children's play area or dispose of in toilet.	Pet wastes left to decompose on grass or soil. Wastes scattered over a wide area.	Animal wastes usually concentrated in a pen. Any droppings on driveway are washed into the street.	High Medium Low
Grass clippings, leaves and other yard wastes	Sweep clippings, leaves and other yard waste off paved surfaces and onto lawns or landscape planters away from water flow routes. Leaves and other yard wastes are composted or used for mulch.	Leaves and other yard wastes piled on the lawn next to the street or in ditches for collection. Leaves or garbage burned outdoors away from paved areas or ditches.	Grass clippings, leaves and other yard debris left on driveways, streets and other paved areas where they will be carried off by stormwater.	High Medium Low

Our goal is to help make you more aware of the problems associated with non-point source pollution from runoff and to help lower your risks of contributing to these problems. The following pages will help provide you with ways to improve on the areas identified as “high” or “medium” risks in the assessment above.

Stormwater is unavoidable, but you can reduce its effects by keeping harmful chemicals and materials out of the runoff. Part 1 reviews the major potential sources of contamination and offers ways to minimize them.

Answer - Most households store lawn and garden products – weed and insect killers, fertilizers, etc. Rain, stormwater or floodwater reaching these products can transport them into surface water or local groundwater supplies.

Answer - A rainstorm can easily carry away oil stains on your driveway, and outdoor spills of antifreeze, brake fluid and other automotive liquids. Runoff from your driveway that has an oily sheen is a sure sign you need to be more careful.

Answer - Droppings from dogs and cats, and from commonly-kept animals like rabbits, goats and chickens, can be troublesome in two ways. First, pet wastes contain nutrients that can promote algae growth if the wastes enter streams and lakes.

Second, animal droppings are sources of disease. Children are more likely to catch a disease from pet waste because it may be in their play areas (sandboxes and swings).

Answer - If left on sidewalks, driveways or roads, grass clippings and other yard wastes will wash away with the next storm. Although leaves and other plant debris accumulate naturally in streams and lakes, you and other residents can contribute excess amounts of plant matter, especially in areas with many homes. This can lead to water that is overfertilized and unsuitable for recreation (like swimming, boating and fishing).

Some stormwater risks can be controlled by changes to buildings, paved surfaces, landscape and soil surfaces. This section reviews some easily addressed problems, as well as major landscape alterations you might want to consider.

Answer - You can find areas of bare soil in vegetable and flower gardens, newly-seeded lawns, steeper slopes and around construction projects. Even on gentle slopes, water from rain can remove large amounts of soil and deliver it to rivers and lakes. Planting grass or other ground covers is the best way to stop erosion. A good stand of thick grass is one of nature’s best filter systems. Putting a straw or chip mulch over gardens or newly seeded areas will slow erosion. Straw bales, diversion ditches and commercially available silt fences around construction sites can help slow runoff and trap sediment on-site.

Answer - Concrete and asphalt roads, driveways and walkways prevent rainwater from soaking naturally into the ground. When you have the choice, consider alternatives such as gravel, wood-chip or brick walk on driveways or patios. Where you need a more solid surface, consider using a “porous pavement” made from porous concrete, interlocking cement blocks, pavers, or rubber mats that allow spaces for rainwater to seep into the ground. If you do pour concrete, keep the paved area as short and narrow as possible.

Answer - Your house roof, like pavement, sheds water. If downspouts from roof gutters empty out on grassy areas, the water will have a chance to soak naturally into the ground. Aim your roof downspouts away from foundations and paved surfaces. This will allow the water that runs off your roof to have a chance to soak into the ground and not simply run off. For roofs without gutters, you can plant grass, spread bark mulch or use gravel under the drip line to prevent soil erosion and increase the ground’s capacity to absorb water.

Answer - An essential part of runoff management is keeping water from leaving your property or at least slowing its flow as much as possible. Many home lawns are sloped to encourage water to run off onto neighboring property or streets. Instead, you could provide low areas landscaped with shrubs and flowers, adapted to temporary wet conditions, where water is encouraged to soak into the ground. If your property adjoins a stream or ditch, or slopes strongly to the street, one of the best ways to slow and filter runoff is to leave a buffer strip of thick natural vegetation along the lower areas. A good source for ideas is the Washington County Extension office (444-1755), Natural Resource Conservation Service or the Soil and Water Conservation District (442-1460).

Pictures of chickens, flowers, wheat, a boy looking through a magnifying glass, irrigation pipe, soybean pods, and fruits and vegetables.	Cooperative Extension Service





Cooperative Extension Service	Agricultural Experiment Station
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Washington County Urban Home*A*Syst What Is Runoff ?

Washington County
Urban HomeASyst
What Is Runoff ?