Riparian Buffer Management Current Knowledge and Standards

Most bodies of water, both running and standing, have a flood plain known as a riparian area. Whether the waterway is a large river or a small, intermittent creek, the water directly affects and is affected by this adjacent land. The riparian area serves as a transition between aquatic and land habitats. It is the link between land and water. When this area is planted in such a way to protect the waterway from negative impacts of the adjacent land use, it becomes a buffer, specifically, a riparian buffer. Recently, we have become aware of several important functions of the riparian areas. They are vital to the conservation of valuable farmlands and essential to the removal of harmful chemicals from our water supply.

Since the turn of the century, during the beginning of the industrial area, lands in the riparian area have been cleared for many reasons and put into other uses, such as pasture, row crops, and storm sewer lines. As our population grew, pressure for home sites has increased and now there are a number of housing developments built in low-lying, flood prone areas. As a result, stream channels have been artificially straightened and deepened to control storm water runoff. The resulting pollutants in runoff are flushed into nearby streams and rivers, by passing natural systems of cleaning. The waters are exposed to much more sunlight as a result of the removal of shade trees, which increases water temperatures, and reduces the number of aquatic organisms, including fish. (Tjaden, 1998). It is essential to maintain and preserve riparian buffer areas in a sustainable manner. This area has brought more attention recently, as a result of public awareness and research projects. New technologies and knowledge make proper riparian buffer management easier than ever before.

By incorporating vegetative riparian buffers along as much of the length of a watercourse as is possible, runoff is intercepted, slowed, and allowed to percolate into the ground, recharging our groundwater. Multiple benefits with minimal expense occur when we allow natural systems such as riparian buffers to function properly.

Different plant materials have different benefits in a riparian buffer area. The following table summarizes the various benefits of grasses, trees and shrubs.

Table 1.

Relative effectiveness of different vegetation types for specific benefits

PRIVATE Benefit

Vegetation Type

Grass

Shrub

Tree

Stabilize bank erosion

Low/Medium

Medium/High

Filter sediment

Low/Medium

Filter nutrients, pesticides, microbes: sediment bound

Low/Medium

Filter nutrients, pesticides, microbes: soluble

Aquatic habitat

Wildlife habitat: range/pasture

Wildlife habitat: forest wildlife

Economic products

Low/Medium

Visual diversity

Flood protection

Source: Adapted from Agroforestry Notes. AF Note-4, Jan 1997. U.S. Department of Agriculture Forest

Using vegetation to stabilize and control or minimize erosion problems near stream banks and their immediate slope area is less expensive than repairing erosion-caused damage. Techniques to stabilize stream banks work by either reducing the force of the flowing water, by increasing the resistance of the bank to erosion forces, or by a combination of the two (Tjaden, 1999).

There are several planting techniques to increase the resistance of the stream bank through binding the soil with root systems and growing a vegetative cover. These techniques are also known as soil bioengineering. They include live staking, conventional plantings, live fascines, branchpacking, brushlayering, and brushmattressing. Once established, this living material effectively controls water runoff and wind erosion, minimizes frost heaving effects by binding the soil with roots; filters soil from runoff; intercepts raindrops, reducing soil erosion; improves rainwater percolation into the ground; and moderates ground and water temperatures (Tjaden, 1999).

Several riparian buffer zone restoration programs have been funded by the USDA to convince farmers of the importance and need to protect and restore these areas. They following was found about these programs (USDA, 1992). The number of farmers participating in riparian buffer zone programs is increasing, the overall level of participation is low. Reasons cited for this low participation rate include, lack of direct marketing of the programs, concerns about ultimately losing control over part of the farm, and the management burden of maintaining riverside fencing (Maille, 2001).

Individualized support is necessary when changing farm management practices. In order to increase participation in this program is it suggested that program strategies that enhance the likelihood that a given farmer will be exposed to examples of buffer zones on farms, and shifting extension staff resources and staff training to increase and improve contacts between the staff and farmers (Maille,...

Another avenue to explore would be to provide the farmer with alternative crops that could be grown in riparian buffer zones, and still provide an income. Some of these crops might include raspberries, high bush blueberries, shiitake mushrooms in shaded areas, and medicinal herbs of commercial value such as ginseng and goldenseal. Other ornamental grasses and forbes might be included as well.
The benefits of the riparian buffer area need to be stressed to the farmer to ensure the success of future efforts. There are ten common benefits to the farmer of maintaining a riparian buffer area. They are: percolation and groundwater recharge is improved, sediment is reduced, excess nutrients and chemical pollutants are filtered, stream bank erosion is reduced, nutrients become available for desired plant growth, flooding is moderated, water temperatures are lowered for habitat improvement, woody and leaf debris contribute to aquatic habitat, more visual diversity and beauty and better habitat and safe corridors for animals (Sneider, 1998).

Aside from convincing farmers to protect their riparian areas, many municipalities and federal agencies can help too. Municipalities have significant capacities to protect stream corridors. Zoning can include minimum stream setback requirements. Many communities require that sensitive lands be subtracted in lot yield calculations. Federal floodplain regulations and state and local wetland protection measures can prevent ill advised development in, and adjacent to, wetlands (Sneider...management, 1998).

There are several guidelines, which should be followed when designing an effective riparian buffer area. You should maintain a minimum 60-foot vegetative filter along the entire length of the stream corridor. Widths should be increased when: soils are gravelly, sandy, and well drained, or have low phosphorus absorption capacity; slopes are steeper (sometimes even 5%); adjacent to sensitive wetlands; or vegetation lacks forest species or grassy strip. When possible, one should attempt to implement a three zone buffer design (15 ft. mature tree edge; 60 ft. strip managed trees and shrubs; 20 ft. grass strip) to remove nutrients, sediment, animal-derived organic matter, and pesticides from surface runoff. For wildlife corridors, or to set back from septic systems, manure concentrations, or other potential water contaminants. You should use a wide variety of native trees, shrubs, and plant species. Choose species, which are tolerant of flooding. Try to prevent channeled storm water from flowing into the buffer (Tjaden, 1998).

The following additional guidelines are suggested by the D.C. Environmental Management Council (2001)

Protected stream corridors should include large trees near the stream's edge to shade the water, maintaining dissolved oxygen for successful fish habitats. Grass Strip Forest Canopy Understory: smaller trees, shrubs, woody plants and grasses Stream Edge: logs, rocks & grasses Aquatic Habitat Stream Bottom Organisms Water Table Subsurface Flow Saturated Zone Towns must determine which waterway corridors are best suited for trails, wildlife routes, or simply aesthetic and water quality buffers" (DCEMC, 2001).

Dr. Mark Roberts has conducted extensive studies on the effects and management of riparian buffer zones. He has found the following to be helpful in establishing riparian buffer zones. He found that it takes approximately 10-15 years to reach its maximum efficiency. This is mostly due to the time required for the perennial plant community to occupy the site and for soil quality parameters to reach optimum levels. Sediment trapping by the native grass component of the buffer may reach optimal efficiency in as little as five years. In addition, he found that nitrates are reduced by riparian buffer systems. Nitrate concentrations are 90% lower and atrazine concentrations 70% lower in the soil water of the unsaturated zone (rooting zone) under the riparian buffers along a creek than under adjacent crop fields. This may not mean that the buffer has removed all of that nitrogen or atrazine from the soil solution but it does represent a zone where nitrogen and atrazine have not been directly applied to the soil. Similarly, nitrate concentrations in the shallow groundwater are reduced by as much as 90% within the buffers (Roberts, 2001).

Under native plant ecosystems (prairie or forest) this nitrate uptake process is slower and the nitrate that is present is rapidly immobilized by the plant or microbial activity. Native ecosystems are said to have a closed or tight nitrogen cycle while present-day agricultural ecosystems are open and leaky. Buffers provide a small, strategically located perennial plant community which can accept a given amount of the leaking chemical load of the rest of the landscape and process it before it reaches the surface and ground waters (Roberts, 2001).

Although a variety of federal and state programs have created and restored riparian buffers in the past, the technical standards used in many of those programs did not always respond to the specific needs and resources of a particular site. For example, they might not have considered the impact of the soil type, slope, and…