The natural
benefits of a riparian (or river) zone can be re-created by planting strips
of trees, shrubs and grasses, and stabilizing streambanks, shown here, as well
as constructing small wetlands to capture tile flow from nearby fields. Source:
Iowa State University, 1995.
What is a riparian zone?
From tiny creeks to major rivers, all waterways have a riparian zone, commonly known as the floodplain. The riparian zone stretches along each waterway and is as wide as where annual or periodic flooding occurs. The riparian zone is the waterway's buffer. Under normal conditions, this land and the "natural" vegetation growing on it traps sediments from upslope erosion, and filters out fertilizers and pesticides used on adjacent farmland. This area may thrive as a very wet area that supports trees, shrubs, grasses, cattails, and other species, or be occasionally wet and support species that can grow under changeable conditions.
In the Midwest, riparian zones support well-known trees such as willow, silver maple, cottonwood, green ash, black walnut, and river birch; shrubs such as serviceberry and dogwoods; and grasses such as prairie cordgrass and reed canarygrass. Most streams in Midwestern agricultural regions now cut deeper into their channels than 150 years ago and, as a result, can support many upland species of trees, shrubs, and grasses if a 3- to 4-ft. deep, well-drained soil exists. Riparian zones also support cattails and bulrushes in calm backwaters and oxbows of large rivers.
Why are they important?
Under natural conditions, riparian zones extend along creeks, streams, and rivers, providing a network of vegetation vital to the terrestrial and aquatic ecosystems.
What happens when they're lost?
Within the last 50 years, natural vegetation of most Midwestern riparian zones has been cleared and replaced by row crops, converted to grazed pastures, or planted to narrow strips of cool-season grasses. Stream channels have been straightened and deepened, and many field tiles that carry agricultural chemicals, such as nitrogen and atrazine, now drain directly into streams. These modifications reduce the length of time that water stays in the soil, where it can be cleaned by the "living filter" of plants and microbes. These changes also have dramatically increased the quantity and speed of water moving in stream channels, which provide more energy for erosion and, in turn, reduces water quality. Stream channels cut deeper to handle increased water flow, which accelerates streambank erosion.
How can they be restored?
While restoration of all natural riparian zones may not be economically or socially acceptable, re-creation of streamside buffer systems along many miles in the riparian zone is possible. A re-created riparian zone managed as a buffer strip system can be established in areas that have been cleared of native vegetation and are no longer functioning properly. This system consists of 66- to 100-ft. wide buffer strips planted to trees, shrubs, and perennial prairie grasses; streambanks stabilized by willow and shrub plantings, and small, constructed wetlands to capture tile flow from agricultural fields.
Restoration and management of existing vegetated areas can lessen, and perhaps reverse, many water quality and environmental problems and, at the same time, increase the quality of life for humans and wildlife. This publication reviews what happens when riparian buffer protection is lost, the benefits of a properly functioning riparian zone, and ways to restore these areas into a healthy system.
Summary
Restoration and management of riparian buffer areas provide many benefits-for the landowner, downstream residents, as well as the rest of the ecosystem. Whether in their natural or in their restored and managed state, riparian buffer systems are true stewards of our streams.