Blasting and clearing of a roadway by a private developer in late 2000 resulted in the destruction of approximately 1000 lineal feet of a native-oak-forested bank along Fox Creek in Eureka, Mo. Forests in this region of the Ozark Mountains are several hundred years of age and have escaped timber harvest due to site inaccessibility. Soils tend to be slightly calcareous, extremely shallow and intermittent, with penetrations through surficial bedrock. High banks and bluffs range from vertical cliffs to one horizontal to one vertical (1H:1V) slopes.
Negotiations with regulators resulted in an action plan to provide restoration of the high bank and stream riffles throughout the impacted reach.
In the interim 18-month period of time between destruction and restoration, natural vegetative succession began with an initial surge of pioneering forbs (foxtail, ragweed, etc.). At the beginning of the second growing season, regeneration of woody perennial from roots began to gain dominance. Restoration was initiated during the dormant season at the start of the third consecutive growing season.

Assessing the Situation

 Bioengineering assay began in November 2001 and determined by agrohistological analysis the presence of seed and tissue of approximately 90 different species of ephemeral, facultative, and obligate forbs, grasses, sedges, and woody perennials. Areas void of vegetative biomass existed in full sun and were confirmed microbiologically as dominated by Azotobacter, a primary aerobic bacterium associated with organic decomposition. Areas containing sprigs and shoots of woody perennials existed near the shade line of the upstream, forested bank and were confirmed microbiologically as dominated by mycorrhizal fungi. As expected, the plant biome was shifting through natural succession from a woodland to a pioneering series. Point and non-point water flow was removing shallow accumulation of topsoil, exposing limestone aggregate.


Designers are often challenged to provide a restoration plan allowing the natural succession and proliferation of native grasses, wildflowers and woody perennials. Too often today we rely on standard specifications using cool season agricultural grasses which serve a primary function of erosion control, at the expense of outcompeting the indigenous species which proliferate in lower fertility soils.
A key concept in design preparation is to determine the biological potential of a soil system. The potential is the summation of agronomic fertility, herbaceous biological diversity, and the impact of environmental forces on the existing ecosystem. Within this biological potential, less invasive restoration technologies provide for revegetation at much smaller plant densities, resulting in the production of biomass in correlation to the nutrient utilization capacity of the site.

RESTORATION PLAN

Plant Materials


Horticulturists and biologists with Terra Technologies surveyed nearby streambanks and identified indigenous species of woodland grasses and understory woody perennials in order to reconstitute the existing seed bank with suitable species. Specific pure lots of material were selected from local collectors based on the percentage of firm (dormant) seed in order to achieve a paradistribution of plant materials for germination each year for six consecutive years. Many native seeds are paragerminating, requiring scarification or stratification for immediate germination. Left in their natural state, many species require 3 to 10 years to achieve full germination within a specific perennial seed crop.


A cover crop of Regreen sterile wheat was utilized for the initial phase of biological erosion control. Wheat hybrid materials tend also to be efficient biological isolators of available nitrogen and phosphorus, providing sustained nutrient release to longer-developing indigenous species upon microbiological degradation. The quantity of seed per square yard was carefully selected to ensure that an adequate population was present to control erosion, while simultaneously ensuring that indigenous perennial species would be exposed to favorable sun and nutrient availability to ensure successful propagation.

Organic Soil Conditioning / Microbial Inoculation


An agronomist and soils bioengineer with Terra Technologies developed the required blend of humates, humic acid, and organic nutrient sources to achieve an adequate microbiological soil environment for the support of indigenous vegetation. Microbial inoculants included specific species of aerobic bacteria, mycorrhizal fungus, and molds. A specific strain of microscopic nematode was also included to provide seed protection from entamogenous degradation.

Erosion Control Technology


Due to slope (0.5:1V), vertical height (65 feet), diverse seedbank, and the lack of a suitable topsoil structure, the requirement for hydraulic distribution of all plant and soil remedial agents was both obvious and mandatory. Bonded wood fiber matrix (BFM) hydraulic mulch was specified at a rate of 4,200 pounds per acre.

About Bonded Wood Fiber Matrix Mulch


Bonded Fiber Matrix (BFM) technology was developed in the 1990s by Weyerhauser and Rantec. The material typically includes an increased quantity of organic tackifier often derived from guar gum that can be 5 to 10 percent of the total BFM product weight. Initial formulations utilized slow release fertilizer compounds and acid catalysts to crosslink the guar which upon curing was rendered insoluble. The crosslinked guar creates fiber-to-fiber bonds which remain intact after wetting and drying, thus resisting non-point source erosion.


Future formulations utilized synthetic fibers in combination with organic tackifiers to further strengthen the matrix and resist erosion when cure conditions were limited. This class of products is often applied to achieve 100 percent soil coverage in areas where biodegradable erosion control blanket installations would be impractical and ineffective. One key reason these BFM systems have worked is that when they are used at high rates of coverage (3,500 pounds and above per acre) they truly form a complete matrix that in combination with much higher rates of tack per acre, can absorb a lot of kinetic energy without exposing the soil to failure.


Work in this specialty BFM venue was field pioneered in the central Midwest by Steve Flick of SA Flick Seed Company in Missouri. Approximately 250 projects have been completed in the states of Kansas and Missouri.

RESTORATION OF BANK

A contract was awarded to Turfmasters Inc. of O’fallon, Mo., to perform the high bank restoration. Utilizing a Finn 3,000-gallon, truck-mounted hydraulic seeder, 30 pounds of pure live native seed with leguminous inoculant was hydraulically broadcast onto the existing slope. Within the mix, one-half pound of Prairie Bundleflower (Desmanthus), a native legume, was scarified and inoculated in order to provide a biological germination marker. An additional 2,000 pounds of GroPower 0-3-1, GroLife mycorrhizal inoculant, cottonseed hulls, and alfalfa meal was broadcast in a separate application after the seed.
The contractor elected to utilize two bonded fiber matrix products for the erosion control technology: Soil Guard, a chemical BFM manufactured by Mat Fiber, and Conwed 3000, a mechanical BFM manufactured by Profile Products. The upstream segment was mulched using Conwed 3000 and the downstream segment was mulched using Soil Guard. Inorganic fertilizer, microscopic nematodes, and 15 bulk pounds of Regreen wheat and wheatgrass were mixed with the BFM. The biological marker was also mixed with the BFM. The material was applied to achieve 100 percent coverage over rock and soil.

RESTORATION EFFECTIVENESS

Unseasonably cool and wet weather occurred in the project area during the first three months. Approximately 19 inches of rainfall occurred within the watershed and a maximum design 25-year storm event occurred approximately 30 days after project completion.


Each segment of BFM application was inspected and surveyed for population of the germination marker. A random selection of three, 4 by 4 square-foot areas within the middle of the project reach was selected, due to similarities in soil characteristics and sun exposure. Within the survey square, the best 4 square feet of plant density is reported to account for variations in soil quality within the survey area. Results were as follows;


Theoretical germination at 100 percent efficiency would produce two plants per square foot assuming ideal broadcast distribution. Germination percentage of scarified bundleflower produced an average of 1.5 plants per square foot (six plants per 4square feet) under greenhouse conditions.


Additional plant material survey indicates the successful first order germination of native grasses including Switchgrass, Canadian Wild Rye, Virginia Wild Rye, and Little Bluestem. Adequate germination of sterile wheat is present. Wildflower populations of brown eyed susan, gray headed coneflower, and pale purple coneflower are evident. Successional propagation of cup plant, native impatiens, hydrangea, mullein, sow thistle, and giant ragweed remain undisturbed, within newly established seedlings of woodland and glade grasses and wildflowers.

A Lesson Learned


Use of mechanical and chemical forms of bonded fiber matrix as an erosion control technology in a high bank restoration project produced favorable results. Adequate population of a germination marker in conjunction with favorable germination on the cover and perennial crops has resulted in the first order propagation of grass, wildflower, wetland, and woody perennial plant materials in an ecologically-sensitive soil structure. Although differences were observed in the population of the germination marker, it is probably statistically insignificant, due to variations in soil conditions. While crude, the germination marker is an ideal alternative for contractor field evaluation of biological product equivalency.


At the time of survey in late June 2002, the development of perennial grasses and wildflowers is occurring without interference to the natural succession of approximately 90 additional species naturally occurring within the seed bank. Additional surveys will be conducted in late June 2003.
Terra Technologies Inc. expresses its sincere appreciation for technical and regulatory assistance provided by Mr. Danny McClendon, Chief, Regulatory Branch, United States Army Corps of Engineers, Saint Louis District.

BIO: David Flick is a principal and founder of Terra Technologies Inc., a bioengineering consultant with offices in Overland Park, Kan., and Saint Louis, Mo. The engineering firm provides design and oversight of more than 60 bioengineering projects each year in the greater Midwest USA. Information about the firm can be found at www.terratechnologies.com.

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