An Integrated Riparian Management System to Control Agricultural Pollution and Enhance Wildlife Habitat

Objective 1 - Demonstrate and quantify the ability of the multi-species, riparian buffer strip to filter, transform, and act as a sink for nonpoint source pollutants.

Description of the Riparian Management System

While a considerable body of evidence confirms that existing vegetated riparian zones have considerable ecological value and can be effective sinks for nonpoint source pollution (Castelle et al. 1994, Osborne and Kovacic 1993, Lowrance 1992, Cooper et al. 1987, Jacobs and Gilliam 1985, Lowrance et al. 1985, 1984, Peterjohn and Correll 1984), little information is available for restored or constructed riparian buffer systems. To demonstrate the benefits of properly functioning riparian zones in the heavily row-cropped midwestern United States, the Agroecology Issue Team of the Leopold Center for Sustainable Agriculture and the Iowa State Agroforestry Research Team are conducting research on the design and establishment of riparian management systems (RiMS). The purpose of these systems is to restore the essential ecological functions that these riparian areas once provided. Potential threats to water quality being addressed by these management systems include surface erosion (Figure 1), streambank and channel erosion (Figure 2), livestock grazing in the riparian zone (Figure 3), and agricultural tile drainage (Figure 4). Objectives of the riparian management system are to intercept eroding soil and agricultural chemicals from adjacent crop fields, slow flood waters, stabilize streambanks, provide wildlife habitat, and improve the biological integrity of aquatic ecosystems.

The initial research site is located on the Ronald Risdal farm along Bear Creek in a highly developed agricultural region of central Iowa. The farm has been owned by the Risdal family for several generations. Corn, soybeans, and alfalfa are produced on this farm with the corn and soybeans rotated on an annual basis. Until 1988, livestock were allowed to graze along parts of the riparian zone. Establishment of the RiMS on the Risdal farm began in 1990. The layout of the site is shown in Figure 5.

The riparian management system consists of three components; a, multi-species riparian buffer strip (MRBS), soil bioengineering technologies for streambank stabilization, and constructed wetlands to intercept and process nonpoint source pollutants in agricultural drainage tile water (Figure 6). The general multi-species riparian buffer strip layout consists of three zones (Figures 7 and 8). Starting at the stream bank edge, the first zone includes a 9 m (30 ft) wide strip of 4-5 rows of trees, the second zone is a 4 m (13 ft) wide strip of 1-2 rows of shrubs, and the third zone is a 7 m (22 ft) wide strip of native warm-season grass. This design is important because the trees and shrubs provide perennial root systems and long-term nutrient storage close to the stream while the grass provides the high density of stems needed to dissipate the energy of surface runoff from the adjacent cropland.

Fast-growing trees are recommended to provide a functioning multi-species riparian buffer strip in the shortest possible time. It is especially important that rows 1-3 (row 1 is closest to the streambank edge) in the tree zone include fast-growing, riparian species such as willow (Salix sp.), cottonwood (Populus deltoides), silver maple (Acer sacharinum), hybrid poplars (Populus sp.), green ash (Fraxinus pennsylvanica), and box elder (Acer negundo). The key to tree species selection is to observe native species growing along existing natural riparian zones and select the faster growing species. If height from the top of the streambank to the water level at normal flow (summer non-flood stage) is more than 1 m (3.2 ft) and soils are well drained, species such as black walnut (Juglans nigra), red oak (Quercus rubra), white oak (Quercus alba), white ash (Fraxinus americana) or even selected conifers can be planted in rows 4 and 5. The slower growing species will not begin to function as significant nutrient sinks as quickly as faster growing species. Other selections could be made based on species growing in neighboring uplands.

Shrubs are included in the design because of their permanent roots and because they add biodiversity and wildlife habitat. Their multiple stems also function to slow flood flows. The mixture of species that have been used by IStART include ninebark (Physocarpus opulifolius), red-osier (Cornus stonifera) and gray dogwood (Cornus racemosa), chokecherry (Prunus virginiana), Nanking cherry (Prunus tomentosa), hazel (Corylus americana), and nannyberry (Viburnm lentago). Other shrubs can be used, especially if they are native species and provide the desired wildlife/aesthetic objectives.

The grass zone functions to intercept and dissipate the energy of surface runoff, trap sediment and agricultural chemicals in the surface runoff, and provide a source of soil organic matter for microbes, which can metabolize the nonpoint source pollutants. A minimum width of 7 m (22 ft) of switchgrass (Panicum virgatum) is recommended because it produces a uniform cover and has dense, stiff stems that
provide a highly frictional surface to intercept surface runoff and facilitate infiltration. Other warm season grasses, such as Indian grass (Sorghastrum nutans) and big bluestem (Andropogon gerardii) and native perennial forbs also may be part of the mix. Because of its growth habit, switchgrass should be used where surface runoff is most severe.

One of the best ways to demonstrate the results of a restoration project is to keep a visual record of the progress of restoration from the beginning of the project. To that end two sets of photos (Figures 9-12) are provided to show visible changes on the site. Because this site was devoid of any significant plant cover other than closely grazed grass and cultivated fields, the change in vertical and horizontal structure of the vegetation community over the first six growing seasons has been very dramatic. This change in structure serves as a physical barrier to both water and wind movement across the buffer strip, provides a diverse wildlife habitat, dramatically changes the aesthetic impressions that visitors have of the site, and suggests that significant biomass can be produced that could provide potential commercial products for the landowner.

Water Quality Monitoring

An important goal of this project is to document and quantify the ability of the MRBS to filter, transform, and act as a sink for nonpoint source pollutants. To accomplish this, water quality is being monitored on a routine basis in the stream, agricultural drainage tiles, groundwater, and within the unsaturated (vadose) zone under the buffer strip. Stream samples are collected twice monthly during the growing season (March through October) and monthly during November through February from three locations within the research site. Samples are collected at the same time from five agricultural field tiles located within the research site. Samples are assayed for nitrate-nitrogen, atrazine, pH, dissolved oxygen, and total suspended solids. Stream and drainage tile discharge are determined at the time of sampling. Deeper piezometers are sampled on a quarterly basis and assayed for nitrate-nitrogen, atrazine, and chloride.

Five transects across one section of the MRBS are being intensively monitored to examine the physical, chemical, and biological processes that occur there. Each of these transects has three nests of sampling devices consisting of a "mini-piezometer" located below the water table, a zero-tension lysimeter at 15-25 cm (6-10 in) below the surface, two porous-cup tension lysimeters at 0.3 m (1 ft) and 1 m (3 ft), and a soil tensiometer at 30 cm (12 in). These nests are located at the crop field-switchgrass interface, within the shrub zone of the buffer strip, and within the tree zone of the buffer strip. During the growing season an additional set of lysimeters is installed within the cropped field along each of the five transects. During 1995, three additional transects containing tension lysimeters at two depths were established in a crop field adjacent to the Risdal farm where the operator cultivates nearly to the streambank edge. Lysimeter nests were installed at the same distances from the stream as those within the MRBS. These transects allow for the comparison of buffer strip function to an area where cropping occurs immediately adjacent to the stream.

During the growing season all instruments within the intensively monitored plots are sampled repeatedly after large precipitation events until the water content of the soil has returned to near field capacity. At other times, samples are collected on the same schedule as stream samples. Water level within the mini-piezometers and several piezometers is measured weekly during the growing season and twice monthy during the months of December - February. Water samples are also collected at the same time from these instruments.

Plant samples of each species in the MRBS, the crop plants growing adjacent to the MRBS, and the cool season grasses within the control plots are collected at the end of each growing season. These samples are assayed for nitrate-nitrogen, ammonia, total (Kjeldahl) nitrogen, and atrazine. A continuously-recording, CR-10 controlled weather station monitors solar radiation, air and soil temperature, relative humidity, wind speed and direction, precipitation, and soil moisture.

Initial results show that nitrate concentrations in the vadose zone are much lower across the buffer strip than within the adjacent cultivated field during both 1994 and 1995 (Figures 13 and 14). Concentrations of nitrate-nitrogen measured within the cropped field were much higher during 1995 than 1994, likely due to the application of urea fertilizer to corn planted in 1995. Regardless of the nitrate-nitrogen concentration measured within fields, however, average concentrations measured within the unsaturated zone nearest the stream never exceeded 3 mg /L.
In contrast, concentrations of nitrate-nitrogen measured in the vadose zone within a field cropped nearly to the stream edge showed no reduction nearer the stream (Figure 15). Differences in the absolute values of nitrate-nitrogen within crop fields (Figures 13 - 14) are likely the result of differences in fertilizer management and soil types. The important distinction between these two sites is the buffering of nitrate-nitrogen concentrations within the vadose zone near the stream provided by the MRBS. In areas where shallow groundwater contributes significantly to stream flow, this buffering function is important in reducing nitrate-nitrogen loads to streams. The lower nitrate-nitrogen concentrations in the vadose zone across the buffer strip are likely combination of the lack of cultivation and fertilizer application within this zone as well the transformation and loss of nitrogen moving through the buffer strip.

Atrazine concentrations in the vadose zone were also much lower across the buffer strip than within the adjacent cultivated field during both 1994 and 1995 (Figures 16 and 17). Atrazine concentrations within the cropped field were much higher in 1995, due to the application of Extrazine when the field was planted to corn. Again, the lower atrazine concentrations in the vadose zone across the buffer strip are likely a combination of the lack of application within this zone, as well the transformation and loss of atrazine moving through the buffer strip. In both cases, in areas where this vadose zone water contributes to streamflow, the presence of the buffer strip will greatly reduce atrazine and nitrogen loadings to the stream. These data do not necessarily reflect the quality of water moving through the shallow groundwater table below the vadose zone. It is possible that agricultural chemicals are leaching through the vadose zones into the groundwater in the crop field and the moving below the MRBS to enter the stream with baseflow.

In assessing the importance of shallow groundwater contributions of agricultural chemicals to the stream, it is important to document the dynamics of the shallow groundwater that may be moving below the MRBS. To accomplish this, minipiezometers were installed in the summer of 1994 across each of the five intensively monitored transects. These instruments are monitored for water level and water quality as described above. The goal of this monitoring is to produce a detailed flow model describing water and chemical movement in the shallow groundwater under the MRBS.

Initial monitoring has provided data to construct preliminary contour maps of groundwater table elevations across the buffer strip (Figures 18 and 19). These maps illustrate that during most times of the year the water table slopes gradually upward away from the stream, under the MRBS and adjacent crop field. During these times this reach of stream would be gaining groundwater as baseflow as indicated by flowlines moving perpendicular to the water table contour lines. In this reach the stream would be considered an effluent stream. A full season of water level monitoring during 1995 also indicates a substantial seasonal flux in the water table with depths to groundwater varying by nearly 1m (3.2 ft). Continued and expanded monitoring is required in order to construct the detailed flow models necessary to accurately describe the shallow groundwater flow beneath the buffer strip.

Nitrate concentrations in the shallow groundwater are highly variable between adjacent transects, and suggest that nitrate contained within shallow groundwater may be moving preferentially across the buffer strip at a depth below the zone sampled by the lysimeters (Figure 20). In contrast, atrazine concentrations are always near detection limits, suggesting little movement of this chemical with the shallow groundwater.
We are expanding our efforts to accurately characterize groundwater and chemical movement across the buffer strip. To this end, we have been successful in obtaining a three-year grant through the USDA National Research Initiative Competitive Grants Program to support these efforts. Initial data collection supported through the Agriculture in Concert With the Environment Program has been instrumental in obtaining these additional resources. The ultimate goal of this research is to characterize the site specificity of nitrate retention and transformation within the streamside buffer strip in order to make credible management recommendations as to their placement and effectiveness.

Objective 2 - Develop a small wetland to intercept and process field tile drainage.
A characteristic of North Central Iowa and much of the prairie pothole region is the presence of an extensive network of subsurface tile drainage. Such tile drains often dominate increases in stream discharge and provide a direct path to surface water for nitrate or other agricultural chemicals that move with shallow groundwater. In such instances, constructed wetlands that are integrated into new or existing drainage systems may have considerable potential to remove nitrate from shallow subsurface drainage (Crumpton and Baker 1993, Crumpton et al. 1993).

To demonstrate this technology, a small, 270 m2 (2900 ft2) wetland was constructed to process field drainage tile water from a 4.9 ha (12 ac) cropped field. The size and shape of the wetland were designed to fit into the 20 m (66 ft) MRBS. Construction of the wetland was completed in early June, 1994. The wetland was constructed by excavating soil near the creek and raising a low berm (Figure 21). Because the site chosen for the wetland contained some alluvial sand, the bottom of the wetland was sealed with clay. Organic soil was then replaced as the top layer. An agricultural drainage tile was excavated and rerouted to enter the wetland at a point furthest from the creek, forcing the water to travel through the wetland before entering the surface waters. A gated water level control structure at the wetland outlet provides complete control of the level of water maintained within the wetland. Cattail (Typha glauca) rhizomes were collected from a nearby wetland during early spring when the shoots had just begun to elongate, and stored in a cooler until planting. These cattails were planted in early June at a spacing of approximately 0.6 x 0.6 m (2 x 2 ft) (Figures 22 and 23). Growth during the initial season was dramatic (Figure 24). The cattails spread rapidly throughout the wetland and many achieved heights in excess of 2 m (6.4 ft). During the following winter and early spring however, many of these cattails were removed by muskrats. As a result, much of the wetland had to be replanted during the spring of 1995. Big bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans), gray-headed coneflower (Ratibda pinnata), and black-eyed susan (Rudbeckia hirta) were planted on the constructed berm to provide vegetation diversity. Establishment of these native grasses and forbs was very successful with all species flowering by the second year. Willow cuttings (Salix sp.) were installed on the side of the berm facing the stream for stabilization.

Water samples at the inlet and outlet of the wetland are collected through the use of automated water samplers. When temperatures prohibit the use of the automated samplers, the inlet and outlet of the wetland are sampled along with routine stream and tile sampling. In 1994, when the field being drained by the tile feeding the wetland was in corn, water samples are assayed for nitrate-nitrogen and atrazine. In 1995, when the drained field was in soybeans, water samples were assayed for nitrate only.

In 1994, inflow concentrations of nitrate-nitrogen in the tile drainage fluctuated between 5 and 10 mg /L NO3--N (Figure 25). In contrast, outflow concentrations were substantially lower during most times. Exceptions to this were in early August and mid-September when large precipitation events increased tile discharge substantially and reduced the residence time of nitrate laden waters within the wetland. Note also that nitrate concentration in the outflow consistently increased during late September and October, reflecting the effects of colder temperatures on denitrifying bacteria.

In 1995, inflow concentrations of nitrate-nitrogen in the drainage tile water fluctuated between 7 and 11 mg /L NO3--N (Figure 26). Similar to 1994, outflow concentrations were substantially lower during most times. Notable exceptions were during early May and early July, again when large precipitation events increased tile discharge substantially and reduced the residence time of nitrate laden waters within the wetland. Precipitation at the research site during the months of July and August, 1995 was substantially below normal. As a result, outflow from the wetland ceased by September 1, and the wetland was dry shortly thereafter.

Concentrations of nitrate-nitrogen in the both the drainage tile water and the outflow decreased rapidly over this period.

Experimental studies by the Iowa State University Wetlands Research Group using wetland mesocosms have confirmed the considerable capacity of freshwater wetlands to remove nitrate (Crumpton et al. 1993) and confirmed that denitrification is the dominant loss process for externally loaded nitrate (Isenhart 1992, Isenhart and Crumpton in prep.). The studies also demonstrate that wetlands containing a large amount of standing vegetation and a large buildup of decaying plant litter will be more efficient in nitrate removal, given sufficient contact time between pollutant laden water and the substrate (Crumpton and Isenhart in prep.). This indicates that wetlands will likely become more efficient at removing nitrate after several growing seasons worth of litter accumulation and may likely take several years to reach a steady state with respect to their nitrate removal capacity.

Rates of nitrate loss in the wetland at the Risdal research site during 1994 and 1995 ranged from 0.3 to nearly 1 gram of NO3--N per square meter of wetland per day. These are comparable to loss rates observed within the wetland mesocoms during the first year after establishment. However, there was little increase observed in nitrate loss rate in the Risdal wetland during 1995. One factor contributing to this was the loss of vegetation within the wetland to muskrats. This prevented the expansion of standing vegetation and buildup of dead plant litter, which would promote higher nitrate loss rates. It is expected that the nitrate removal capacity of the wetland will increase as the wetland matures and accumulates this litter layer of dead plant material. Removal rates of nitrate within the wetland can be expected to increase in 1996 as the vegetation density increases.

The ratio of wetland surface area to area of crop field drained for the Risdal wetland is 1:180. Previous studies suggest that a mature, one hectare wetland could remove significant amounts of the nitrate in water draining approximately 100 ha of corn at moderately high N application rates (Crumpton et al. 1993, Isenhart 1992). The Risdal wetland is, therefore, below this benchmark ratio, and it remains to be seen what the maximum retention capacity for nitrate will be once the wetland reaches maturity. Models have subsequently been developed of areal nitrate flux which can be combined with models of wetland hydrology to produce general models of nitrate loss and assimilative capacity for freshwater wetlands (Crumpton and Baker 1993). These models will be utilized to interpret data from the Risdal wetland.

In the case of atrazine, concentrations were very low (< 0.5 μg /L) in both the tile inflow and outflow to the stream for most of the monitoring period during 1994 (Figure 27). The notable exception to this was in late September, when inflow concentrations in the drainage tile increased to over 1.5 μg /L. During this time atrazine concentrations in the wetland outflow remained below 0.75 μg /L as a result of both dilution and retention within the wetland.

Objective 3 - Demonstrate the ability of a combination of willow posts, stakes, and cuttings to act as a durable and environmentally acceptable system for long-term stabilization of eroding stream banks.

The objectives of streambank stabilization efforts are to reduce sediment loading to the stream originating from streambank erosion, and to stop the movement of the bank. In some cases, bank movement may be encroaching on fields, bridges, and roads. In other cases, channelized stream sections may start to again meander. The stabilization of streambanks is accomplished by changing the steep angle on actively eroding banks to a gradual slope on which woody or other perennial plants may seed themselves or be planted. Deeply-rooted plant material will help hold the soil of the streambank in place. Woody plant roots have the advantage that they are perennial and provide long-term strength to the soil, even during the winter and early spring. Woody stems of willow and other species provide a dense frictional surface that slows the water impacting the bank and moves the rapidly moving current out away from the streambank. The slower water moving through the stems drops sediment. The accumulating sediment changes the slope of the bank and provides sites for other native plant establishment. A characteristic of perennial grasses that become established along the bank is that they do not slow the water as much and typically lay down along the bank, allowing rapid movement of water while yet protecting the bank. This use of grasses may be important in reaches where there is concern that channel flow should not be slowed.

Stabilization of streambanks using bioengineering methods also provides wildlife habitat improvements. Aquatic habitats may be improved when shaded conditions stabilize water temperature. Inputs of organic matter from the litter of the overhanging plants also provide substrate for aquatic invertebrates. In some cases, woody debris dams, which may develop from fallen stems or beaver dams, may be beneficial. In other cases, especially in some cold water fisheries, the presence of woody stems provides material for beaver dams that produce pools in which accumulating sediment covers gravel streambeds.

Streambank bioengineering projects must consider the objectives of the landowner, the size of the stream, the stream fishery, the stability of the channel bottom, and the severity of the streambank erosion. Each design must be site specific. The goal of this project has therefore been to demonstrate a number of different designs to address the many variables that must be considered at each project site.

For small streams, those in which the top of the bank is 1.2 m to 1.8 m (4 ft to 6 ft) above the normal water surface, stabilization can often be accomplished simply by installing live posts, stakes, and cuttings along the bank toe and in the vertical wall of the streambank. On slightly higher banks or larger streams, dead tree revetments can also be installed to stabilize the toe of the bank. Willows are recommended because they root easily and multiply quickly under the often harsh conditions found along an eroding streambank. However, other species can be used. Cottonwood (Populus deltoides) cuttings may root well in the upper banks and dogwoods (Cornus spp.) may be used above the willow posts. Use of dogwood reduces the shading of the stream and may discourage beaver activity.

For this grant, variants of two different methods of bioengineering were developed on four sites. To demonstrate the use of willow posts and tree revetments, two 80-100 meter long stream bank willow plantings and revetments have been established on the outside bends of two severely eroding stream banks on the Risdal project site (Figure 5). On the first site, willow stakes and posts were manually pounded into the stream bottom, the toe of the bank, and on the vertical wall (Figures 28 and 29). The willow cuttings were collected during the dormant season by harvesting willow stems and cutting them into 0.6 - 1.2 m (2 - 4 ft) lengths. During the second year, a revetment of silver maple bundles was added along the toe of the bank. The silver maple revetments are composed of bundles of 3-8 year old trees that were wired together and then piled and anchored to fence posts that were pounded into the bottom of the stream bank. On the first site, revetments were only added along the toe of the bank. Figures 30 and 31 show the response of this bioengineering technique after 2 and 4 years.

On the second site, the revetments were piled higher to protect the 2.1 - 2.4 m (7-8 ft) high vertical bank (Figure 32 and 33). On both sites, willow posts and stakes were manually installed into and around the revetments and in the rest of the vertical bank. These revetments of living and dead trees provide a dense frictional surface to dissipate the energy of the stream and allow the willow cuttings to become established. The willow posts and stakes sprout quickly (Figure 34 and 35), producing a vegetated surface that adds a living and dynamic frictional surface to slow the flow and protect the bank. Both of these sites have withstood major flood events, including the major floods of 1993. Costs associated with installation of these systems are presented under Objective 5.

Along streambanks that are greater than 1.8 m (6 ft) in height or on larger streams, additional techniques may have to be used, including the use of some non-biological material. To demonstrate these techniques, two additional sites, a 76 m (250 ft) long site on the Larson property and a 46 m (150 ft) site on the Risdal property, have been installed. Figures 36 - 43 show the installation of the system on the Larson property. Major considerations for that installation are listed below.

• Because the streambank was steep (Figure 36), a backhoe was used to slope it to a 1:1 (horizontal:vertical) angle (Figure 37). A slope of 2:1 may be required for taller streambanks.

• The toe of the slope was stabilized by cabling Eastern redcedar to fence posts (Figure 38). Alternatively, the Eastern redcedar could have been cabled to willow posts installed in the streambed. After the first storm event the redcedars are buried with enough sediment that they will no longer move. A shallow trench 45 - 60 cm (1.5 - 2 ft) wide and 15 - 20 cm (6 - 8 in) deep was dug at the base of the slope in which to bury the end of the geotextile installed to protect the face of the slope. A waterway grass seed mixture was spread over the exposed bank at a rate of 5.6 Kg /ha (5 lbs /ac).

• The geotextile was installed up and down the slope, beginning at the downstream end of the site. The top sheet of geotextile was overlapped 15 - 30 cm (1/2-1 ft) over the bottom sheet and degradable staples were inserted along the overlapped area. Additional wire staples were installed on a 0.6 x 0.6 m (2 x 2 ft) spacing over the whole slope (Figure 39). If the slopes had been sloped to 2:1, geotextile may not have been necessary. Alternatively, more willow and/or dogwood cuttings would be planted.

• Live willow fascines were prepared and placed in the trench along the bottom of the slope (Figure 40). This securely anchors the geotextile to the soil. The fascines were covered with soil allowing only a small portion of the willow to be exposed to light. The willow in the fascines developed roots and sprouts, which effectively anchored the mat to the bottom of the bank. Figure 41 shows the streambank stabilization structure during higher water that occurred during construction.

• Willow posts were installed through the fascines and in three rows along the bottom of the bank at a spacing of 0.9 m (3 ft) between trees and 0.9 - 1.2 m (3 - 4 ft) between rows. Additional stakes were installed above the posts to the top of the slope. Another shallow trench was prepared at the top of the slope, into which the top end of the geotextile was buried. Finally, a multi-species buffer strip was planted along the top of the slope (Figure 42). Growth after two months showed grass coming through the mat and sprouting of the willow (Figure 43).

Installation of the soil bioengineering demonstration on the Risdal property is shown in Figures 44-49. The major differences in this installation are that rock rip rap was used to stabilize the toe of the slope instead of Eastern redcedar, and no fascines were used to tie the geotextile to the slope. Instead, the geotextile was buried in a trench dug along the bottom of the slope and willow posts installed along the trench. The trench is wide enough to form a lip on which a person could walk to fish the stream. The grass and willows on this installation have grown exceptionally well. While this installation may be more than was necessary to protect this streambank, it was installed to provide a demonstration on the Risdal property where most of the field tours are taken and where the other RiMS components are demonstrated.

The effectiveness of these streambank bioengineering options is being monitored by comparing treated stream sections with several unprotected banks of similar curvature and length along Bear Creek. Permanent cross sections have been established and surveyed in order to measure the movement of the creek. Initial results are very encouraging and visual observations suggest bank collapse has been dramatically reduced.

Three other uses of bioengineering have also been demonstrated on the project sites. Figure 50 shows the use of only Eastern redcedar as a bank stabilization technique. After installing rock rip rap for toe control, Eastern redcedar trees were cabled to the vertical bank. This system was installed in 1995 and seems to be holding. Figure 51 shows both the more intensive design that includes the geotextile and the simpler Eastern redcedar installation. Both systems are being monitored to see how effective each is in maintaining streambank stability.

Figure 52 shows the effectiveness of willow stakes that were installed on a four foot high bank just downstream from a bridge on the Risdal farm. The bridge was washed out after the 1993 storms. After it was rebuilt, the channel cross-section was changed enough so that the bank on the right started to show accelerated erosion. Willow stakes of 0.6 - 0.9 m (2-3 ft) length were installed to slow the erosion. This low cost method is very effective, if installed when the problem is first evident.

Figure 53 shows the use of willow posts installed across a gully. The posts are installed as close together as possible and bound together with twine. An Eastern redcedar is cabled into the gully upslope of the willow to slow the water before it reaches the willow posts. This installation was completed in May of 1995.

Soil bioengineering technologies are proving to be very effective at streambank stabilization on second and third order streams. Further testing and demonstrations are needed, however, on larger size rivers. We will be conducting such a test in 1996 on the Volga River in Northeast Iowa. Costs for the soil bioengineering systems that have been described are presented under objective 5.

Objective 4 - Evaluate the impact of the MRBS, the field tile wetland, and the stream bank willow planting on wildlife habitat and use.

Wildlife habitat in much of the corn belt of the Midwest has been impacted greatly by intensive row crop agriculture. Riparian areas that once had diverse tree, shrub, and native grass cover are now grazed or cultivated. Such areas provide little nesting cover or food to maintain a diverse wildlife population. The riparian management system being developed on Bear Creek was specifically designed in part to enhance wildlife habitat. For example, shrubs have been incorporated in the design for their diversity in habitat as well as for their food production.

To document its habitat value, bird species composition within the MRBS was assessed and compared with species composition in a contiguous, channelized section of stream with little riparian cover (downstream) and in an upstream section which was planted to a MRBS early in 1994 (Strum farm). The newly planted site contains some tight meanders along which willows and other trees and shrubs were established. It therefore had some available habitat even before the MRBS was planted.

The three study areas were divided into 17 fixed observation points beginning with the Strum farm and numbering downstream (Figure 54). Location of observation sites were based on differences in dominant cover, i.e. Site 1 was located in unmanaged, mixed grasses; Site 12 was located in an area of willows and a wetland. Observations were extended to a radius of 50 m (160 ft) from the center of each site except for sites 16 and 17. This exception was made because of the homogenous plant structure and unbroken visual distance along this portion of Bear Creek (brome grass buffer strip 5 m wide).

Observations were made over a total of 10 days beginning 15 June 1994 and ending 11 July, 1994. Starting observation sites were varied each day as a means of balancing patterns in bird species activity associated with microclimate and onset activities (Karr and Freemark 1983). Species observations were noted from two points within each site for a total of 10 to 15 minutes. Species were counted as present if either visually observed or their song was heard. All observations were made by the same individual, and only those species positively identified were counted. No attempt was made to measure species density. The presence of nesting was noted, but no intensive search for nests was undertaken.

Results demonstrate that MRBS construction increased bird species diversity dramatically and in a short period of time. On average, four species per day were found on the channelized section, 14 species per day were found on the newly planted MRBS (Strum farm), and 18 species per day were found in the four-year old MRBS on the Risdal farm (Figure 55). These observations translate into nearly 4.5 times more bird species using the MRBS site compared to the channelized reach. A two-sample comparison at the p<0.05 level indicate that these differences in bird species diversity are significant.

The total number of bird species observed throughout the study period was also much greater within the MRBS site (Table 1). Within the channelized section, a total of 8 species were observed throughout the study period. Within the newly planted MRBS site (Strum farm) and the four-year old MRBS (Risdal farm), these numbers increased to 24 and 30 species, respectively.

Sorenson's coefficient of community was applied to assess differences in bird communities observed in each of the three management areas along Bear Creek. Sorenson's index is defined as cc=2c/(s1 +s2), where cc is the coefficient of community, c is the number of bird species held in common in two sites to be compared, s1 and s2 are the total numbers of species accounted for in each site. Results indicate that there was a strong similarity between bird communities using the Strum and Risdal sites, as indicated by a Sorenson value over 86%. In contrast, there was little similarity in bird communities observed within the channelized area compared to the Strum and Risdal sites, as indicated by Sorenson values of only 42% and 41%, respectively.

Many factors will affect the diversity of bird species observed in a given area. These include the size of the habitat area, individual species' habits, land management practices, predation, time of day, weather, and others (Smith and Shugart 1987). Analysis of community similarity infers that the Strum and Risdal areas share factors that may be influencing bird species. These factors might include the width of habitat area, vegetative structure and species diversity, similarities in older, woody vegetation, increased foraging areas, or even less tangible influences attributed to such factors as increased invertebrate assemblages (Smith and Shugart 1987, Rafe et al. 1985). One factor contributing to similarity between the Risdal and Strum sites is the presence of existing woody (tree and shrub) vegetation on the Strum site.

Dissimilarity in bird species composition between the channelized area and the Risdal area may be attributed to the width and structure of the riparian vegetation. The MRBS established on the Risdal farm is nearly four times as wide as the grass-only buffer of the channelized area. These results would agree with those of Stauffer and Best (1980) who found that "bird species richness increased with the width of wooded riparian habitat." The lower vegetation complexity found along the channelized portion of Bear Creek may also negatively affect bird species by exposure to greater daily temperature/precipitation changes, decreased food availability, increased vulnerability to predation, and other microhabitat variations (Ambuel and Temple 1983, Stauffer and Best 1980).

Several factors that may have affected observed species diversity were neither vegetational nor climatic. For example, several locations within the study area were periodically mowed to aid the establishment and growth of planted tree and shrub species. Another factor to be considered is the presence of several free-roaming dogs within the Risdal area. The ability of the dogs to locate and rouse nesting species was witnessed several times during the observation period. On observation days, care was taken to avoid attracting the dogs by entering the study area away from the Risdal site proper. Both of these factors may have negatively impacted ground-nesting bird species on the managed areas; thus we regard these species diversity measures to be conservative.

Vegetation diversity within the MRBS appeared to directly effect the patterns in diversity. For example, observation sites situated on either side of Risdal wetland possessed a greater species richness. Similarly, an observation site containing two large, standing dead trees attracted a very diverse composition of birds. Also, bird species observed in and around the dense willow plantings established for streambank stabilization were seldom found elsewhere. These species include Parus atricapillus (Black-capped Chicadee), Carduelis tristis (American Goldfinch), and Spiza americana (Dickcissel). These findings are consistent with other studies (Rafe et al. 1985)

Although community indices are not widely accepted as the sole indicators of habitat complexity, this study strongly suggests that the multi-species riparian management system positively influences bird species diversity. Future areas of study should include analysis of management effects on breeding birds as well as examination of the correlation that apparently exist between bird species diversity and the various vegetation components of multi-species management.

[Table 1 shows bird species noted in each study area in early summer along Bear Creek in central Iowa. Since it is not possible to render this table here, we offer a list of all the species observed at all sites:]

Agelaius phoeniceus, Red-winged Blackbird
Anas discors, Blue-winged Teal
Carduelis tristis, American Goldfinch
Ceryle alcyo, Belted Kingfisher
Charadrius vociferus, Kildeer
Cistothorus platensis, Sedge Wren
Cyanocitta cristana, Blue Jay
Dendroica petechia, Yellow Warbler
Dolichonyx oryzivorus, Bobolink
Geothlypis trichas, Common Yellowthroat
Hirundo rustica, Barn Swallow
Melospiza melodia, Song Sparrow
Molothrus ater, Brown-headed Cowbird
Parus atricapillus, Black-capped Chickadee
Passerculus sandwicensis, Savannah Sparrow Phasianus colchicus, Ring-necked Pheasant
Pooecetes gramineus, Vesper Sparrow
Progne subis, Purple Martin
Quiscalus quiscula, Common Grackle
Sayornis phoebe, Eastern Phoebe
Spiza americana, Dickcissel
Spizella passerina, Chipping sparrow
Spizella pusilla, Field Sparrow
Sturnella magna, Eastern Meadowlark
Sturnus vulgaris, Euopean Starling
Tachycineta bicolor, Tree Swallow
Toxostoma rufum, Brown Thrasher
Turdus migratorius, American Robin
Zenaida macroura, Mourning Dove

Mean species per day:
Risdal 18.2
Strum 13.9
Channelized 4.1

Objective 5 - Evaluate the costs of establishing and maintaining the three riparian management systems being demonstrated on the Risdal farm.

Multi-species Riparian Buffer Strip

Costs of establishment and maintenance of each of the components of the RiMS are being determined on an ongoing basis. In addition, Mr. Risdal is continuing to supply his costs for producing corn and soybeans. Costs for establishment and maintenance of the multi-species riparian buffer strip have been estimated using 1994 and 1995 costs and prices. Tree seedling costs were based on prices from the Iowa Department of Natural Resources State Forest Nursery. Switchgrass seed costs were based on local agricultural seed supplier prices. Site preparation costs were based on the Iowa State University Extension Service 1994 Iowa Custom Farm Rates adjusted for inflation. The site preparation for trees and shrubs assumes a 1.5% concentration of glyphosate applied in a narrow strip and for switchgrass either cultivation and disking or a broadcast of glyphosate before drilling. Planting and maintenance costs were based on 1994 local custom prices for those services. Maintenance costs were based on spot spraying glyphosate and some mowing for competition control in the tree and shrub rows for the first 5 to 8 years and harvesting (or burning) of switchgrass on an annual basis.

Establishment costs reported here are for a 66 ft (20 m) wide multi-species riparian buffer strip which has 8 ft. (2.4 m) between rows and 4 ft (1.2 m) between trees within a row. The total establishment cost is approximately $538 /ac. To provide a conservative estimate, the costs used are "high-end" costs. For example, it is assumed that the seedling cost is $0.22 each. Some Midwestern private nurseries charge $0.12 for the same tree seedling. The cost of planting varies as well from a high of $0.20 per seedling to $0.105 per seedling. Because the plant material and planting costs are the predominant cost components, actual per acre costs are likely to not exceed the stated costs. Tables 2a and 2b present the establishment costs for various riparian buffer strip designs to be established on agricultural land that is currently being cropped or pasture land.

The estimated establishment and maintenance cost does not include any existing governmental cost-share or other subsidy. Currently, there are several cost-share programs available that will cover up to 75% of these expenses. The Stewardship Incentive Program (SIP) administered by the Iowa Department of Natural Resources will cost-share up to 75% of the establishment cost of a buffer strip not to exceed $315 per acre. Also, SIP will provide 75% of the cost of fencing the buffer strip to keep out livestock, if necessary, not to exceed $45 per acre. Finally, SIP will provide 75% of the cost of shelters for trees planted in the buffer strip, not to exceed $150 per acre. Additionally, in Story County, IA, Pheasants Forever (a non-governmental organization) will cost share another 15% for the purchase of plant materials used in a buffer strip.

A multi-species riparian buffer strip can qualify as a "Forest Reserve" under the Iowa Forest Reserve Law. This means that the land on which a qualifying buffer strip exists will not have property taxes. To qualify a multi-species riparian buffer strip must contain the equivalent of 200 trees /ac, be more than 2 ac (0.8 ha) in size, and have livestock kept out of it. For Iowa this means a cost-savings of roughly $15 - 20 per acre per year.

Tables 3 a and 3b present the discounted costs of establishing 1 acre of riparian buffer strip on cropped land and grazed (pasture) land over a 20 year period. Note that the 1994-5 average rental rates for cropped and pasture lands for Central Iowa were used to determine the total present value of costs. By including the rental rates, the primary opportunity cost of installing a riparian buffer strip on existing agricultural land is included.

If a riparian buffer strip was established along the main channel and tributaries of Bear Creek at either 33 ft., 66 ft., or 100 ft wide on both sides of the stream, how much would the farmers and society have to pay? Table 4a presents the estimates of establishing and maintaining such buffer strips over a 20 year period. Clearly, the wider the buffer along Bear Creek, the greater the cost. The question then becomes whether the value associated with the expected flow of environmental and market benefits from the buffer strip greater than this cost, including the opportunity cost of not farming the land immediately adjacent to Bear Creek. When biomass from trees and switchgrass are valued over a 20 year period at $15 per ton, total present value of cost is reduced by 6 percent at a 5% discount rate. Although not included in the analysis, hunting and aesthetic value, and cost-share options from non-governmental organizations such as Pheasants Forever can further reduce the total cost to the farmers and society for buffer strip protection that complements best management practices on the uplands. Establishing a 66 ft wide buffer on Bear Creek would convert about 445 acres of currently cropped or pastured land.

Table 4b illustrates what the cost would be if the protection effort was focused on the lands adjacent to Bear Creek that are classified as potential or highly erodible lands (HEL). Establishing the 66 ft wide buffer would convert only 45 acres of cropped or pastured lands in the watershed. Obviously the costs of protecting HEL lands within the watershed are much smaller and so too are the expected benefits from reducing non-point source pollutants.

Streambank Stabilization

The following cost estimates are based on the streambank bioengineering portions of the RiMS project located in rural Story County, Iowa. Over the preceding three years, IStART and the Agroecology Issue Team have installed seven different streambank bioengineering systems on Bear Creek, a second order stream that is a part of the Skunk River watershed. The streambank bioengineering systems that were added to Bear Creek were designed and installed by Richard Schultz, Joe Colletti, Tom Isenhart, Chuck Rodrigues, and numerous Iowa State University students. Material and installation costs were recorded during the installation of each of the different streambank bioengineering systems.

This portion of the report is organized by presenting a short explanation of how and why to install each system followed by a table listing all materials required to install such a system. The materials are then converted to a cost per linear foot of streambank. Each table is followed by a list of the citations of sources that were used for the costs cited.

Some assumptions were made for transportation, cost of tools, and labor. Transportation is based upon the number of miles that willow, Eastern redcedar, and silver maple are carried to the installation site. It is assumed that these trees can be found within five miles of the installation site. If they are not within five miles, the cost per linear foot will increase. Likewise if they can be located closer than five miles the cost per linear foot will decrease.

The cost of the small tools, hammers, gloves, shovels, etc., are calculated on the basis of the average life expectancy of each tool. For example, hammer costs are based on a five-year life expectancy. A small equipment cost was calculated for each different component of the streambank bioengineering systems and added into the cost per linear foot. For example, separate costs were calculated for willow post cutting and installation, preparation and installation of fascines, cutting and installation of Eastern redcedar, and installation of the geotextile. For each of the seven streambank bioengineering systems that were installed, equipment costs were added based on the number of components that were used in the system. For example, if a fascine and willow posts were used, the cost of small equipment for each of them was added into the total cost of the system. This accounting for the same small equipment twice would increase the cost per linear foot when actually the cost per linear foot should go down. The cost for small equipment should decrease, because the equipment was already purchased and available for use with both components. When summing the cost per linear foot for a streambank bioengineering system that has several different components, the cost per linear foot may be inflated. Costs per linear foot were calculated in this manner to best show estimates of cost per linear foot for each individual component of the system.

Costs that are incurred for labor to collect, prepare, and install streambank bioengineering systems can be greatly decreased if volunteers can be found. Labor can come from hiring persons at an hourly rate or contacting local conservation groups that may volunteer their time. Conservation groups and interested private persons may help install a streambank bioengineering system so that they gain experience with constructing such a system. Whenever possible conservation groups should be contacted for help with installation so that the cost is reduced. However, as acceptance of these systems becomes more widespread, there will be a need for training contractors who will routinely and professionally install these systems.

All of the listed streambank bioengineering systems should be planted in the spring, from late March to early May. Nearly all systems use live willow and other material that should be planted early to survive through the summer.

Geotextile Costs

Geotextiles, or fabric manufactured from natural fibers such as coconut fiber, are used to protect the exposed streambank from rainfall impact and high channel flows after reshaping has occurred. Reshaped streambanks are very susceptible to erosion because the soil has been disturbed. To reduce damage by erosion, the newly sloped streambanks may be covered with a natural fiber fabric. Trenches are dug at the top and bottom of the streambank to install the edges of the fabric so that it cannot be ripped out during high streamflow. Willow posts or stakes are planted through the fabric in the trenches and waterway grass seed mixes are sown under the fabric to ensure quick revegetation of the site. The fabric is designed to decompose in two or three years, well after the grasses, shrubs, or trees have become established.

The use of geotextiles as a component of streambank bioengineering constitutes a major cost per linear foot. The cost of the fabric, based on two projects in central Iowa established in 1995 on Bear Creek, was $2.34 per linear foot. This represents 62% of the total cost of a particular installation. Another substantial cost in this component of a streambank bioengineering system is the labor. The labor cost for installing a geotextile is $1.01 per linear foot or twenty-seven percent of the total cost per linear foot. While there are other fabrics that could be used, we only have data on the coconut geotextile.

Site Preparation Costs

Site preparation entails reshaping the streambank with a backhoe. If the top of the streambank is higher than 6 ft above low flow in the channel and the walls are vertical or nearly so, then the streambank must be reshaped. Without reshaping, the streambank will continue to slough until a slope angle develops on which vegetation can become established. Stability can be achieved through natural processes over time as the stream and streambank have time to equilibrate. This process of equilibrating takes a very long time during which the channel may move significantly. It is also possible that the system will continue to be in a state of flux and stability may never occur, especially if the banks are high and vertical. To hasten stabilization a backhoe can be used. The streambank is usually reconstructed to a 2:1 ratio of horizontal to vertical length. At this ratio and with vegetation cover, a stable slope can be developed.

The cost per linear foot of reshaping the streambank varies with the contractor. Expect to pay between $0.55 to $1.00 per linear foot. These costs are estimated from the IStART project that was installed in the spring of 1995. The cost varies with the ratio of horizontal to vertical slope that is desired. If a 1:1 ratio will suffice, then less soil has to be moved and less time will be spent with the backhoe reducing the cost.

Costs for Eastern redcedar Tree Revetments

Eastern redcedar (Juniperus virginiana) trees can be used to reduce the erosive power of stream flow along the toe of streambanks. Eastern redcedar trees are preferred because they have a high leaf surface area that is retained for long period of time after harvest. Some consider Eastern redcedar to be an undesirable species throughout much of the Midwest, and, therefore, it can usually be obtained for free.

Eastern redcedar trees are installed along the toe of the streambank, which is susceptible to scour. If the toe of the streambank is not stable, then any bank work done above it has a high possibility of being undercut and eroding into the channel. Willow posts and metal fence "T-posts" are a small selection of the many methods to secure the trees to the toe of the streambank. The Eastern redcedar trees are anchored to the willow posts or T-posts using wire or twine, making sure to have the butts of the trees pointed upstream. Open grown Eastern redcedars, at least 10 ft in height, are best suited to this practice because they have a full complement of branches and needles along the main stem of the tree.

It is imperative to get the Eastern redcedar anchored into the bottom of the streambed right along the toe of the bank to insure that undercutting does not occur. It is also very important to tie the Eastern redcedar into the streambank at the upstream end of the bioengineering system. If this is not done high velocity streamflow will get behind the installed Eastern redcedar and undercut the bank. To decrease the possibility of the stream cutting behind the Eastern redcedar trees, it is necessary to lengthen the upstream end of the Eastern redcedar tree installation as well as the rest of the streambank bioengineering system past the point of streambank failure by 10 to 15 feet. The same precautions should be taken on the downstream end of the bioengineering system, although given time and budget limits the upstream end is more critical. Once the Eastern redcedar trees have been installed, it is good to install one row of willow posts within the trees at a spacing of 2 to 3 ft between willows.

Costs for this portion of a streambank bioengineering system are dependent on distance, method of hauling, and size of the trees. Before selecting this component for a streambank bioengineering project, be sure that a source is located five miles or less from the project site. Labor can constitute between 50% and 60% of the cost of an Eastern redcedar tree streambank bioengineering component based on costs incurred in the IStART projects.

Fascine Costs

Fascines can be an important component of a streambank bioengineering system. Fascines are long bundles of willow tops, the small unused sections of the thinner stems of the willow trees that were harvested for posts and cuttings. Fascines are placed into a shallow trench at or above the normal flow stream depth. The purpose of using fascines is to produce many willow shoots and roots in the area where the fascine is placed. Within one month after placement of a fascine, willow shoots emerge producing a carpet of grass-like willow sprouts that root into the streambank and stabilize the soil and anchor the geotextile.

Construction of fascines is accomplished by grouping the dormant willow tops into a one-foot diameter by twenty foot long bundle. Twine is wrapped around the bundle to aid in stability when moving the fascines into the streambank bioengineering system. A shallow trench, into which the fascine is placed, is dug in the bank just above normal streamflow. To ensure that the fascine does not move during high stream flows, just after planting, willow posts or wooden stakes are driven into the fascine at 4 ft intervals. Soil is spread over the fascines to reduce the possibility of drying out. Care must be taken to cover the fascine lightly with soil. Growth will not occur if too thick a layer of soil is used. At least the top few twigs of the bundle should have access to daylight.

Fascine costs are dominated by the cost of labor, as calculated from the installation of a fascine in the IStART project. Thirty to fifty percent of the cost of installing a fascine can be accounted by the cost of labor. The price for willow can also greatly affect the cost per linear foot of a fascine component in a streambank bioengineering system. The willow used in a project like this can come from the tops of the willows harvested for the posts or cuttings that are usually used in conjunction with the fascine. If the tops from willows harvested for posts and cuttings are utilized, then the cost of the fascines are greatly reduced.

Costs for Installing Willow Posts and Cuttings

Willow posts and cuttings are the most common components of a streambank bioengineering system. Willow posts and cuttings are simple to prepare and install. They are used because they root easily from hardwood cuttings. Groves of willow can be found within five miles of a project site along nearly every waterway, though not all may have the size of trees needed for longer and larger posts. Collection of the willow occurs during the dormant season, late fall until the middle of March depending on the location of the project and the weather. Once the willow has been harvested, it should be stored in the dark at temperatures of 40° F or lower and kept moist. If the stated conditions for storage are met, the willow material will last well into the spring planting season.

Willow trees can be easily prepared for installation. The trees are cut into three different types of planting material depending on the project. There are posts, cuttings and material for fascines. Posts are larger in diameter, greater than two inches in diameter and four feet or more in length. Posts may be up to six inches in diameter and 8-10 ft in length. Cuttings are smaller than two inches in diameter and up to four feet in length. Cuttings and posts should be free of all branches before planting. If the posts and cuttings are to be stored for three or more weeks before planting they are best left in whole tree lengths or the longest length that can be transported. This will reduce any drying of the stems that might occur during long periods of storage. Trees can be cut to the proper length just before installation. Before a post or cutting can be planted, they should be soaked in water for up to twenty-four hours. The posts should be sharpened on the end that will be driven into the streambank. Once the planting material has been soaked and sharpened it is ready for planting. Willow posts and stakes and cuttings should be planted with the correct end up so that rooting and sprouting can occur. In other words, the willow will not grow if planted upside down.

Posts are planted in the streambed and the toe of the streambank because they are stronger and longer. They should be planted as deep as needed to reach a solid streambed material that will not be influenced by the turbulence of streamflow. The deeper the post is planted, the less chance the post will be removed by flood waters. The rows of posts planted in the streambed will probably only live for two to three years. During this time they serve the important purpose of slowing the water until the posts at the toe of the bank have become established.

Installing the posts is achieved by one of the following methods: pounding the post with a sledge hammer, drilling holes with an auger and placing the posts into the holes, or punching a hole into the streambank with a metal probe and then placing the post into the hole. The auger and metal probe in the last two methods are usually mounted on a backhoe. Whatever method is used, be sure the post is planted deep enough so that it will not be removed by flood waters and the buds are pointed up. Usually two rows of posts are planted in the streambed with one or two more planted in the toe of the strreambank. These plantings are on a 3 x 3 ft spacing.

Willow cuttings are planted into the streambank above the posts all the way up to the top of the streambank on a 3 x 3 ft spacing. The cuttings are inserted into the streambank as far as possible, at least two feet or more deep. Only two or three buds should to be above ground for the cutting to survive. The deeper the material, post or cutting, is inserted the better.
The cost of labor constitutes the majority of the cost per linear foot when collecting, constructing, or installing willow posts or cuttings. If willow material can be found that is free of charge, the cost per linear foot can be reduced considerably.

The following tables give numerous possible combinations of willow posts and cuttings. An example of how to calculate the cost of a willow post and cutting system follows in the last table.

Cost Example

The following is an example to show how to add costs for three rows of posts and four rows of cuttings, if they are planted together on the same day and the willow is obtained free of charge. Costs are presented on a per-linear-foot of streambank.

Collection and Installation
* three rows of posts: $2.26
* four rows of cuttings: $1.53

Cost of willow material
* three rows of posts: $0.44
* four rows of cuttings: $0.58

Total for three rows of posts: $2.70
Total for four rows of cuttings: $2.11

Total per linear foot for three rows of posts and three rows of cuttings: $4.81

Rock Rip Rap

Rock rip rap is used in streambank bioengineering systems to stabilize the toe of the streambank in situations where Eastern redcedar is not available or where a stronger toe control system is desired. The rock is hauled to the site and a backhoe places the rocks into the stream. The rock should be placed in the streambed at the base of the toe of the bank and extend two to three feet up the toe of the slope above normal stream flow levels. In some cases it may be necessary to dig a trench in the streambed to assure that the rock makes contact with solid streambed material. It is also important to assure that the upstream and downstream ends of the rip rap are tied into the streambank so that streamflow cannot scour behind the rip rap. The size of the rock should be large enough so that the rock is not moved during flood flow. There are many charts and tables that will determine the size of the rock that should be used for a certain sizes of streams.

The cost per linear foot is most influenced by the cost to haul the material to the site. A local source of rock should be located before using this component of a streambank bioengineering system. Hauling the rock for the system installed in Story County accounted for 30% of the cost per linear foot.

Maple Bundle Costs

Silver maple (Acer saccharinum) is used to create bundles that act to armor vertical streambanks and allow for planting of willow posts and cuttings. These bundles are composed of dead trees that are not expected to sprout, but provide temporary protection until they decompose or the associated willow plantings have become established. The bundles have gaps that allow willow posts and cuttings to be planted right through the bundles and into the streambed and streambank. Armoring the streambank acts to reduce the stream velocity of water that directly hits the streambank. If the velocity is reduced, then there is less erosive energy that could damage the streambank.

Silver maples were used in constructing bundles in the IStART projects because they were available and of the correct size (three to six inches in diameter and 15 to 20 feet long), but any multi-stemmed trees would work. The key is getting large amounts of material with as little effort and cost as possible. Multi-stemmed trees yield large amounts of material with little work. Once the trees have been cut, bundles of five to seven trees are wired together with electric fence one-fourth gage or similar wire, every five to seven feet. Be sure the wire is tight so that when in the stream flood water will not tear the bundles apart.

To install the bundles, metal T-posts or willow posts must be driven into the streambank about every five feet from upstream of the eroding streambank to down stream of the eroding streambank to be protected. The bundles are placed next to the posts and wired to them. The posts can also be driven through the bundles, instead of next to them to increase the stability of the bundles against flood flows. The first bundle row must be at the toe of the streambank. The bundles should cover one-third to one-half of the streambank to ensure streambank stability. The tighter the bundles are placed next to the streambank, the lower the risk of scouring under and around the bundles. Bundles should be used in conjunction with installing willow posts and cuttings.

The cost of using tree bundles is expensive on a per-linear-foot basis. Costs are high because this form of streambank bioengineering is labor intensive. One-half of the cost to install a bundle system is spent on labor, based upon costs incurred on the bundle systems installed in the IStART projects. Constructing, installing, and positioning the bundles is difficult because of the size and awkwardness of the material.

Constructed Wetland

Establishment of the wetland cost approximately $2800. Most of this cost ($2400) was associated with excavation charges. As mentioned, due to the presence of some alluvial sands at the chosen site, several truckloads of clay were required to seal the bottom of the wetland. In many areas this may not be required and construction cost would be substantially reduced.

Objective 6 - Develop appropriate technology transfer materials and activities for farmers, policy-makers, farm groups, and others.

Another objective of this project has been the encouragement of the adoption of the riparian management system through a number of technology transfer activities. We have been very active in trying to get the story told to as many audiences as possible. A complete list of technical and news articles published, presentations, workshops, conferences and other means of educating diverse audiences on project findings is included below under Section B - Dissemination of Findings. Additional technology transfer activities include:

Educational brochures. A integrated series of educational brochures is being developed to be distributed through the ISU Cooperative Extension Service and USDA-Forest Service - Northeast State and Private Forestry. These brochures will also be distributed at all field days and presentations. The series is entitled "Stewards of our Streams" and will include the following publications:

Stewards of our Streams: Riparian Buffer Systems. Pm-1626a

Stewards of our Streams: Buffer Strip Design, Establishment, and Maintenance.
Pm-1626b

Stewards of our Streams: Streambank Stabilization. Pm-1626c

Stewards of our Streams: Restoring Wetland Buffer
Areas. Pm-1626d

Stewards of our Streams: Financing Riparian Restoration Projects. Pm-1626e

The initial brochure, Stewards of our Streams: Riparian Buffer Systems is an introduction to the series and gives an overview of riparian zone function and management. This twelve page, four-color brochure is complete, with 5,000 copies printed. A copy has been included in Appendix IV.

The subsequent two-color brochures will provide technical detail on each of the specific topics related to riparian zone management and restoration. The second brochure in the series, Stewards of our Streams: Buffer Strip Design, Establishment, and Maintenance, is in the final production stages. The final draft of this publication is currently being reviewed by the Iowa Department of Natural Resources and the USEPA Region 7 Office. A copy of the final draft of this publication is included in Appendix IV.

A preliminary draft of the third publication in the series, Stewards of our Streams: Streambank Stabilization, is complete. This publication is being co-sponsored by the Leopold Center for Sustainable Agriculture.

Prior to the development of the Stewards of our Streams series, preliminary versions of the educational brochures were distributed to all field day attendees, made available at all presentations, and mailed upon request. These preliminary educational brochures were entitled "Your guide on how to make a riparian buffer strip" and "Design and establishment of a multi-species riparian buffer strip." We estimate that over 5000 copies of these materials have been distributed.

Field Days. We estimate that over 800 individuals have visited the project site during the last two years as part of the more than 30 formal tours that have been hosted. Two of these tours have been field days organized for local landowners and citizens. One field day, jointly sponsored by the Leopold Center for Sustainable Agriculture, Iowa State University Extension, and the USDA-NRCS offices of four Central Iowa counties, was held on August 30, 1994 and was attended by nearly 80 people. Attitudes and impressions of field day participants were assessed through the means of a follow-up questionnaire mailed to all attendees and are summarized in Farmer Evaluations/Testimonials [not available online]. A second field day, in the form of a streamside tour and dinner for landowners and farmer/operators in the Bear Creek watershed, was held on September 7, 1995. Copies of the invitation notices for these two field days are included in Appendix IV.

Among others, the project site was also visited by the State of Iowa Natural Resources Commission, the State of Iowa Soil Conservation Commission, 45 farmers attending a crop production workshop sponsored by Iowa State Cooperative Extension Service, 60 people attending the Leopold Center for Sustainable Agriculture Annual Conference, 50 conservation professionals attending the Annual Meeting of the Soil and Water Conservation Society, and 34 individuals attending the National Conference of Landscape Architecture Educators. A complete list of tours, field days and educational visits to research sites is included under Publications/Outreach.

Self-guided Trail. A self-guided trail has been established at the Risdal research site, which includes stops illustrating the buffer strip, steambank stabilization technologies, and the wetland. In addition, the trail has stops at a two-year old buffer strip immediately upstream from the Risdal site (on the Strum farm) and at small prairie restoration. A copy of the self-guided trail brochure is included in Appendix IV. An information kiosk with a 4' by 8' display area is used to provide further information to individuals touring the site. This kiosk can also be used to present information specific to each tour being hosted.

Video and Slide Set Production. A 70-slide set has been developed and is used extensively by project personnel. This slide set has been duplicated and has been sent to numerous persons or groups around the country for use. In addition, plans for the next year include the development of a 15-20 minute video. The video will assess present conditions of mismanaged riparian zones, describe how an effective buffer strip functions, show before-and-after footage of successful MRBS (from the Bear Creek site), and describe how to construct a MRBS management system. This video will be used by extension specialists, coop agronomists, FFA and high school teachers, and others to make meaningful presentations to a wide variety of audiences. This video would be a part of displays at major meetings such as the 1996 Farm Progress Show to be held in Amana, IA and the Iowa State Fair. This video will be supplemented with the various bulletins produced in the objectives described above. These initiatives are also being supported by the Agriculture in Concert With the Environment Program through Project Number LWF 62-016-03028.