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Erosion control practices in the United States are driven mainly by concern about the impact of accelerated erosion and sediment on the quality of the nation's waterways and reservoirs. Suspended solids and turbidity drive up water treatment costs; sedimentation results in loss of aquatic habitat, reservoir capacity and hydraulic conveyance.

Pesticide and fertilizer residues that are attached to eroded soil particles in urban and agricultural runoff, pollute lakes and streams. The Federal Water Quality Control Act of 1987 attempted to deal with these non-point pollution problems.

Agriculture still contributes the largest amount of sediment to the nation's waterways: an estimated 2 billion tons per year. This finding is not surprising because agriculture constitutes the largest single land use by a wide margin.

The picture changes dramatically, however, when comparing erosion on a rate basis, in tons of soil eroded per acre per year. In this case, urban construction sites and road projects on average generate much more erosion than crop lands. This spells trouble for areas undergoing rapid urbanization.

Many new erosion control techniques and products have appeared on the market during the past decade in response to public concern and government legislation with

regard to erosion. These products greatly expand our capabilities to combat erosion problems. We should not lose sight, however, of fundamental erosion control principles that must underlie and guide any successful erosion control program.

Erosion control measures basically fall into two major categories: measures to decrease erosive forces on the one hand versus measures to increase erosion resistance on the other. Measures to decrease erosive forces mainly entail decreasing the velocity of water (or wind) flowing over a bed of soil and/or dissipating the energy of the water in a defended area.

A grade stabilization structure shows a good example of this approach. Measures to increase erosion resistance basically consist of stabilizing the soil and/or covering the soil surface with a protective layer. Biotechnical composites such as erosion control and turf reinforcement mats are good examples of this approach. regard to erosion. These products greatly expand our capabilities to combat erosion problems. We should not lose sight, however, of fundamental erosion control principles that must underlie and guide any successful erosion control program.

Erosion control measures basically fall into two major categories: measures to decrease erosive forces on the one hand versus measures to increase erosion resistance on the other. Measures to decrease erosive forces mainly entail decreasing the velocity of water (or wind) flowing over a bed of soil and/or dissipating the energy of the water in a defended area.

A grade stabilization structure shows a good example of this approach. Measures to increase erosion resistance basically consist of stabilizing the soil and/or covering the soil surface with a protective layer. Biotechnical composites such as erosion control and turf reinforcement mats are good examples of this approach.

The latter take advantage of protective benefits provided by both a vegetative and structural coverage.

Dense covers of grass and herbaceous plants provide the best single protection against surficial erosion. Plant leaves and foliage intercept raindrops; the stems and roots filter sediment out of the runoff; the roots tend to reinforce the soil and and bind the particles together; furthermore the stems and foliage increase surface roughness and slow the velocity of runoff.

Vegetation by itself also has certain drawbacks: it takes time to establish and is vulnerable initially to washout and/or drought. A variety of techniques and products have been developed to overcome these limitations. "Reinforced grass" refers to a grass surface which has been artificially augmented with an open structural coverage (mats, meshes or interlocking concrete blocks) to increase its resistance to erosion above that of grass alone.

Biotechnical composites which provide this reinforcement are composed of non-degradable elements which furnish temporary erosion protection, enhance vegetative establishment, and ultimately entangle themselves with living plant tissues (roots) to extend the performance limits of vegetation. Biotechnical composites include such products as erosion control revegetation mats, turf reinforcement mats and vegetated geocellular containment systems.

Soil bioengineering can also enhance the performance of vegetation. Soil bioengineering uses living plant materials, i.e., stems and branches, as the main structural components or reinforcements in the soil mantle. Live cut stems are purposely arranged and embedded in the ground in various configurations. Techniques such as brush-layering and contour wattling work on this principle.

Embedded live cut stems and branches provide immediate reinforcement; secondary stabilization occurs as a result of adventitious rooting which develops along the length of the buried stems. Soil bioengineering methods find increasing application as a cost-effective and environmentally attractive method of combating both stream bank and hillside erosion problems. LASN

The 27 acre Nancy Creek Nature Preserve was once predominantly a 100 year flood plain. Now, thanks to a year-long cut and fill operation and the efforts of Landscape Architect Jim Teller, there is a 558 unit mid-rise community and a new wetland area designed to catch and retain flood water. The site contains sixty thousand Juncus effusus, or Soft Rush (see photo top right) to bind the soil and provide a stable, erosion resistant base. The project was recently recognized by Barbara Bush at the Nurserymens AAN 31st National Landscape Awards Program . Today, blue jays, brown thrashers and geese are a common sight, enjoyed equally by residents of the Post Chastain apartments and the local community.

At Tampa's Lowry Park, what was once a jumble of broken concrete and old bricks (below) is now a beautifully renovated example of proper planning and the employment of erosion control technology. Thanks to the new Mayor, Sandra Freedman, and the Surface Water Improvement and Management (SWIM) program administered by the state, the 1/4 mile of shoreline along the Hillsborough River incorporates five different erosion control methods to preserve the pristine environment.

Most of the riverbank was graded to a 6:1 slope and planted with native materials in zones according to each plants' natural relationship to the water. Where a 6:1 slope with all vegetation was not possible (above), a 4:1 slope with rocks backed by geotextiles was used.

To prevent over erosion from boat wakes, baffleboards were used under the boardwalk (left) to dampen the waves effect on the structure and the shoreline.

At Tampa's Lowry Park, what was once a jumble of broken concrete and old bricks (below) is now a beautifully renovated example of proper planning and the employment of erosion control technology. Thanks to the new Mayor, Sandra Freedman, and the Surface Water Improvement and Management (SWIM) program administered by the state, the 1/4 mile of shoreline along the Hillsborough River incorporates five different erosion control methods to preserve the pristine environment.

Most of the riverbank was graded to a 6:1 slope and planted with native materials in zones according to each plants' natural relationship to the water. Where a 6:1 slope with all vegetation was not possible (above), a 4:1 slope with rocks backed by geotextiles was used.

To prevent over erosion from boat wakes, baffleboards were used under the boardwalk (left) to dampen the waves effect on the structure and the shoreline.

Jute mesh (Left) and integrated geotextiles (right) provide stability to a slope while encouraging vegetation to flourish. The jute is often bio-degradable allowing nature to take control within 6-8 months. Geotextiles are mostly non-degradable and provide years of back up and support to steep hills or along riverbanks such as at Lowry Park.

Seed is usually broadcast before the netting is laid. However, several new products are available with seed already incorporated in the mesh. At Lowry Park both bio and non-degradable materials were used in addition to open cell precast concrete mats, rip rap and natural vegetation.

When people first drove into Hartford, Connecticut on I-91 South, they saw an 85 foot high, 2,000 foot long mound of garbage. This 100 acre landfill could be viewed by over 50,000 people a day.

In 1988, the landfill was chosen as a demonstration site for both slope stabilization techniques and selection of plant materials that beautify as well as survive the harsh conditions found at landfills.

The project consisted of many sponsors, among them the International Erosion Control Association (Southern New England Chapter), the Connecticut Resource Recover Authority, the Hartford County Soil and Water Conservation District and the USDA Soil Conservation Service.

A five acre site along the slope was chosen for the demonstration. The goals included controlling the serious surface erosion that exposed refuse within the landfill; stabilizing the slope to permit establishment of vegetation; and establishing selected plantings to present an attractive appearance.

A uniform application of seed, lime and fertilizer was applied to the five acre site. The seed mixture, included Kentucky 31 Tall Fescue, Red Fescue, Perennial Ryegrass and Birds foot Trefoil.

Soil scientists with the Connecticut Agricultural Experimental Station in Windsor, gathered information on plants that could survive the methane gas that chokes their roots and the carbon monoxide released by heavy I-95 traffic.

This list of garbage proof plants, included tree of heaven, sumac, and flowering shrubs like forsythia, dogwood and climbing shrub rose. A curvilinear design from along the whole mound created a flowing, ribbon-like effect, aimed at producing massing on the mound as well as color along the highway.


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November 19, 2019, 1:49 am PDT

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