WASHINGTON Healthy turf offers more than a pretty green carpet and playing field. Lawn can protect against erosion, provide oxygen, trap pollution and even slow fire.

Of course, some would rather not have a lawn. Some don’t want the responsibility of caring for it. Environmentalists say turf can be responsible for runoff of nutrients and pesticides into rivers and streams.

I embrace another perspective, that lawns and their alternatives can both be good ideas. People who want turf for recreation and those who desire natural habitats can each have their way. But exposed soil must be covered, or it will erode. Here are some suggestions for covering the earth and ensuring that you are helping the environment:

One way to put turf to use on a sloping property is with a sodded waterway, which can help control erosion.

Maintain a gradual slope, which will slow down the flow of storm water and allow it to percolate, filtering sediment and lawn chemicals.

A steep property might require contouring the lawn in a series of 25 percent slopes 10 feet long, broken up with five-foot-wide, almost level terraces to slow the water and divert it to the sides.

Soil coverage is crucial. Maintaining healthy turf and creating balanced native-plant communities will help control topsoil loss. Lost soil, in the form of clay and fine sand carried by storm water into lakes and rivers, makes water too shallow for aquatic life.

Another method of soil coverage is native grass.

Some grasses you can try that are native to the United States are buffalo grass, blue grama and crested wheat grass. All are indigenous to Midwestern and Western states. They will be looser and more open than a typical lawn but will need little care once established. Try them, and see which ones do well for you.

• Buffalo grass (Buchloe dactyloides). Resistant to heat and drought, buffalo grass tolerates warm seasons and grows four to five inches tall. It can be planted from seeds but spreads slowly. A native of the Great Plains, it does not perform well in poorly drained or extremely sandy soils. It prefers well-drained clay loam, with supplemental watering in severe dry periods.

• Blue grama (Bouteloua gracilis). Tolerant of heat and drought, blue grama withstands cold temperatures. It goes dormant and turns brown in severe droughts, but it will return to blue-green with some water in cooler temperatures. Blue grama, which is low-growing, establishes well from seed. It takes a little time to begin in spring and makes a fuller lawn when planted with buffalo grass.

• Crested wheat grass (Agropyron cristatum). An exceptionally hardy clump-forming grass, it is used as turf in Wyoming and will become dormant during hot spells. It doesn’t need much mowing.

If you find that you are having difficulty establishing a lawn, perhaps it’s time to consider a rain garden. You can create beautiful gardens; replace a lot of lawn; and keep water and sediment on your property that would otherwise flow into streams, rivers and lakes.

Rain gardens are installed using many methods. The primary one is called bioretention, in which plants, microbes and soil are used to treat storm-water runoff. Larry Coffman, Prince George’s County, Md., head of environmental programs, developed the principles of bioretention in 1990. Since then, his ideas and research have spread around the world.

Rain gardens can cover large or small areas and can collect, divert or channel precipitation. They can be employed in urban, suburban, industrial or rural settings.

Common rain-collection devices include cisterns, rain barrels, runoff ponds, swales and irrigation ditches. One typical style of rain garden is a shallow basin.

A book that covers the subject thoroughly is Rain Gardens: Managing Water Sustainably in the Garden and Designed Landscape, by Nigel Dunnett and Andy Clayden. This 188-page book has 165 color photographs and 40 line drawings (Timber Press, $35).

For another excellent resource, download The Bioretention Manual of Prince George’s County, Maryland at www.raingardens.org (choose “Rain Garden History” from top links bar). This 60-page manual explains the science of channeling and using rainwater.

The most important aspect of installing a successful rain garden is to ensure that water flows where you want it. Here are several rules developed to ensure that bioretention areas drain properly:

• Water flowing into rain gardens must percolate so there is no standing water left within four hours. A six-inch-deep rain garden filled to the top should drain at a rate of 1 1/2 inches an hour.

• Rain gardens must be installed at least four feet above your water table and should be at least 100 feet from a well.

• The slope into a rain garden should be no steeper than a 20 percent grade.

• Keep rain gardens at least two feet from property lines. Make sure that overflow will discharge in a safe direction, such as planting beds. Direct it away from structures.

The expression “you never miss the water till the well runs dry” is true. We have taken the availability of clean water for granted. Think about it the next time you shower, brush your teeth, take a drink, or watch a plant as it wilts and dies for lack of moisture. Consider the consequences for us.

Joel M. Lerner is a member of the Association of Professional Landscape Designers, president of Environmental Design in Capitol View Park, Md., and author of Anyone Can Landscape.