1. Project Title: Soil Bioengineering for Streambank Protection and Fish
Habitat Enhancement
2. Contact
Rick Grillmayer, Habitat Projects Coordinator
Collingwood Harbour Remedial Action Plan, 275 First Street, Unit 6,
Collingwood, Ontario L9Y 1C1
Tel.: (705) 446-0551; FAX: (705) 446-0561
3. Agencies Involved
Nottawasaga Valley Conservation Authority, R.R. #1, Angus, Ontario L0M 1B0
Ministry of Natural Resources, Midhurst, Ontario L0L 1X0
4. Restoration Goal
To repair and stabilize eroding streambanks through the use of vegetation, and to create instream cover by the construction of vegetated structures.
5. Project Type
Streambank stabilization, instream habitat creation, riparian enhancement.
6. Background and Rationale
The Black Ash Creek Project was initiated in 1992 as a component of the Collingwood Harbour Remedial Action Plan. The objectives of this project were to reduce sediment loading from the creek into the harbour and to enhance fish and wildlife habitat (Dobbs and Grillmayer 1994). Black Ash Creek contributes approximately 90% of the suspended sediment load for Collingwood Harbour (Collingwood Harbour RAP Stage 2 Document 1992). Sources of this sediment include erosion induced by cattle grazing steep escarpment areas, and eroding streambanks.
Soil bioengineering was chosen as a method of streambank stabilization for several reasons:
1. It is an applied science that combines structural, biological,
and ecological concepts to construct living structures for erosion,
sediment and flood control (Sotir and Gray 1989). Conventional
methods of erosion and flood control (gabion, rip-rap, concrete
vertical) provide little in habitat for terrestrial or aquatic
organisms. These structures often have the effect of an
ecological barrier, separating aquatic and terrestrial. Because
of the vegetation used in bioengineered structures, they tend
to provide a wide range of habitat types for many organisms.
2. Bioengineered structures are labour intensive, not capital or energy intensive. Limited budget dollars was put into wages, not materials.
3. Because the structures are growing, they will require less long-term maintenance that conventional structures. Bioengineered structures also tend to be self-repairing.
This submission to the methods for habitat modification manual is based on the projects used on two sites: the Thompson Property (Site 1) and the Ferguson/Garbutt Property (Site 2).
Site 1
The erosion at this site was exacerbated by the channelization of the stream. The reduction of channel sinuosity, and the elimination of floodplain functioning had created an unstable reach of stream. Because the channel had been placed in a roadside ditch, the shoulder of the road (Conc. 10, Nottawasaga Twp.) was also eroding. A previous attempt to stabilize this channel with field stone failed because passersby on the road would remove this stone from the channel. Since the stream gradient was steep (3.1%) once the bed armour had been removed the streambed degraded, and this aggravated the eroding bank. The bank slope on both sides was near vertical.
Bank stabilization and streambed armouring took place during the fall of 1993.
Site 2
The stream channel on this property was heavily laden with debris. A large logjam had forced flood flows into a high sandy bank, eroding the soil and causing the bank to collapse. This collapse toppled large numbers of trees, which in turn increased the size of the logjam. Because of the debris and associated sediment deposition, the spawning and rearing habitat available to migratory rainbow trout was limited. The sediment and debris also had a negative impact on the other fish species present in Black Ash Creek.
Initial debris removal took place during the summer of 1992. Bank stabilization and habitat improvement works took place during the summer of 1992, and the spring of 1994.
7. Regulatory Considerations
a) Project was approved by the local Ministry of Natural Resources (Midhurst District), and a work permit issued under the Lakes and Rivers Improvement Act.
b) A permit from the Nottawasaga Valley Conservation Authority was required under Fill, Construction, and Alterations to Waterways Regulations.
8. Criteria
Site 1
The primary intent of this project was the stabilization of the eroding bank. Because the stream channel at this site is intermittent, habitats created were for the most part terrestrial. The desired stabilization technique would use vegetation as the primary support, rather than inert materials such as quarrystone or concrete.
Site 2
Rehabilitation efforts on this site were to achieve an increase in the population sizes of the fish species present in Black Ash Creek by creating a stable reach of stream characteristic of a typical 2nd or 3rd order stream. It was felt that, by achieving this goal, we would also partially reduce the amount of sediment contributed by that reach of stream to the harbour. Parameters that we decided upon for construction were:
1. re-exposing of rock/gravel substrates;
2. selective opening of the forest canopy to stimulate riparian and instream plant growth, without thermal loading;
3. use of vegetation and onsite materials for construction;
4. use of in-channel sediments both onsite and upstream to build-up intream structures;
5. where possible the use of native or naturalized plant species.
9. Project Design
Site 1
The confined nature of the channel prevented us from excavating a flood plain, or from sloping the banks to a stable angle. The east side of the channel was privately owned, and the owner was not open to the loss of property that would occur if regrading were employed. On the west side of the channel was the concession road, so regrading was also not an option. It was decided to construct a Bioengineered cribwall. This structure can be used to stabilize a vertical bank, and requires little room. The streambed was armoured to prevent down cutting. No attempt was made to stabilize the road shoulder.
A bioengineered cribwall is a hollow, interlocking arrangement of timbers, constructed as a wall (Figure 1). This structure is filled with suitable soil and layer of live branch cuttings. Once the cuttings have taken root and grown, they will eventually take over the structural functions of the timbers. The end result is a stable, vegetated slope.
Site 2
We attempted to stabilize the bank by removing the instream debris, and by creating a low revetment wall at the base of the slope. The wall was built to a height well below the bankfull flow. This level was selected so flood flows could easily overtop the structure and enter the floodplain behind it. Spawning habitat would be reestablished were it was previously covered in debris. The eroding bank would be stabilized using bioengineered fascines, erosion control blankets, and seed mixtures.
A fascine is a long bundle of live cuttings bound together in a sausage-like structure. Fascines are effective in stabilizing slopes prone to shallow slides, and prevent the forming of shallow rills. They also are effective in stabilizing the toe of a stream bank.
10. Implementation
Site 1
The cribwall was built into the bank so that the face of the wall was at the same location as the face of the slope. This was done so that the capacity of the channel would not be reduced. A hi-hoe was used to excavate the cribwall site. The logs for the crib were cut from an NVCA jack pine plantation. The wall itself was built by hand, and measured 40 m long, 1 m high, and 2.2 m deep at the bottom. The wall was canted back so that top brush layers would not shade bottom ones.
Shrub willow cuttings were harvested from sites within the watershed and transported to the cribwall site. Care was taken to time the harvest so that only fresh material would be used. Species of willow used at this site were:
Willow Salix eriocephala
Sandbar willow Salix exigua
Autumn willow Salix serrisima
The cribwall was built in alternating layers of timbers, soil, and cuttings. Once the crib was completed, unused soil was removed from the site. Exposed soil was seeded with annual rye and oats, then covered with anti-wash geojute to prevent surface erosion. Live stakes (live rootable cuttings tamped into the ground) were placed at random in the jute.
The streambed was built up and protected from down cutting by placing 28 tonnes of rip-rap stone. Rip-rap stone was used instead of riverwashed or field stone because it is not as attractive, and therefore less prone to removal by motorists.
Because of the absence of any horizontal sinuosity, stream energy had to be dissipated by vertical sinuosity. This was achieved by placing the stone in a series of steps, attempting to establish a step-pool formation that is common to high gradient streams.
Photographs 1-5 show the site from pre-construction to finish.
Site 2
The first step at this site was to remove the instream debris (logjam), and any fallen or leaning trees. This material was either removed from the floodplain or stored nearby for later use. A low retaining wall was then constructed at the toe of the eroding bank, no higher than the bankfull mark. Open spaces behind this wall were filled with brush and debris taken from the debris removal. This material was used because the site was not accessible by machinery, and all works and to be completed by hand. The surface of the fill was left rough in order to catch sediments moving downstream during floods. This capturing of sediments would fill in all of the open spaces, and allow vegetation to succeed into the structure (Photograph 6).
The retaining wall was designed to undercut, so that it would create instream cover.
The eroding bank behind the wall was graded (slightly as it was done by hand) then seeded with a commercial grass seed. Once the seed was placed the entire bank was then covered with a monofilament based erosion control blanket.
Several current deflectors were built downstream of the retaining wall. These deflectors were constructed with a low profile, and were designed to work in a similar manner as the retaining wall. Coarse sands and silt were trapped by the defector, the vegetated by grasses and sedges, becoming part of the streambank.
During the spring of this year fascines were added to the slope
to repair a section that had slumped during the previous fall.
A fascine was also added to the crest of the retaining wall to
provide more support, and to add a more vigourous vegetation type.
The fascines were made using the same species of shrub willow
as the cribwall. Typically the construction of bioengineered structures
requires the use of dormant materials. dormant material is used
because plant species that root from cuttings typically root better
when dormant. The period of dormancy for shrub willows in this
part of Ontario is typically late October to early April. Unfortunately
for this project that also coincided with fall and spring high
water levels. To avoid this, material was harvested during the
early spring, placed into cold storage (to remain dormant) then
used in the field once
conditions were satisfactory.
Photograph 7 shows the site prior to debris removal, and photograph 8 shows the same site during the following summer.
Photograph 1.
Photograph 2.
Photograph 3.
Photograph 4.
Photograph 5.
Photograph 6.
Photograph 7.
Photograph 8.
11. Degree of Environmental Intervention
Site 1
The stream at this site is intermittent. The fish community (cyprinids, catostomids) is non-existent during the summer, fall, and winter. Fish are present, likely as migrants, during the spring. The cribwall was built during the fall, while the channel was dry. Sedimentation was minimal, and the addition of bed materials would have affected no fish or macroinvertebrates.
Terrestrial habitats were disturbed during excavation of the site. Several fallen trees were removed by the contractor. A Woodchuck used the face of the cribwall as the entrance to it's burrow, and could be seen feeding on the developing willow shoots. The wall was not damaged by this browsing.
The materials used in the cribwall were native, and harvested from within the same sub-watershed as the cribwall site. The disturbed soils above the wall were seeded with annual rye and oats. These species were selected as they provide immediate cover, but as annuals will allow native (or naturalized) plants to take over the site.
Site 2
Initial debris removal occurred during the summer months, well after the emergence of rainbow trout (this was an MNR requirement). Instream habitat was altered by the debris removal, but this alteration was mitigated by the re-appearance of spawning substrates, and the creation of an undercut bank. Sedimentation of downstream habitats was minimal, partly because of the installation of downstream deflectors, and the low height of the retaining wall, captured much of the coarse material that was released.
As in the cribwall site, all material used was either native or naturalized to the area.
12. Cost
Site 1
Thompson Property Cost/Time Requirements
Effort
Effort is given in person hours or p/h. It is broken down into the various commitments required by the project. Measuring and Design includes time spent with consultants, township superintendents, landowner contact, and securing of contractors and materials. Site preparation involved working with the contractor in removing trees, grading the site, and the placement of the riprap in the streambed. Placement of the material is the construction of the wall.
Requirements (Person/Hours)
Measuring and Design: 48
Site Preparation: 27
Cutting/Transporting Material: 48
Placement of Material: 108 (40)*
Repairs to Lawn: 12 (60)*
Total 243 + (100)* = 343
* Time spent by the Salvation Army Intermittent Program. This is classed as voluntary.
Costs: Wages
Wages are broken down as to Field Supervisor (FS) and Crew (C).
Requirements Wages
Field Supervisor Crew Total
Measuring and Design $772.00 $772.00
Site Preparation $161.00 $150.00 $311.00
Cutting/Transporting Materials $193.20 $360.00 $553.20
Placement of Materials $434.70 $810.00 $1 244.70
Repairs to Lawn $48.30 $90.00 $138.30
Totals $1 609.20 $1 410.00 $3 019.20
Materials
NOTE: Costs do not include: tools, truck rental, fuel, office costs, indirect support for the crew, or permit fees. It would be impossible to separate these cost as they were used, or required on more than one site. Costs listed here where specific to this site only.
Materials Description Cost
Consultants Harrington and Hoyle Ltd.
- consultation on design and construction. $800.00
Logs for Cribwall Free !! from NVCA, Cost is for transport to site. $50.00
Contractors Paul Forbes Construction.
- highhoe, backhoe work, haulage of leftover fill. $1 423.10
Plant Cuttings Free !! Cost is for the rental of the
clearing saw used in harvesting. $300.00
Rock Seely and Arnill - 22 mt of riprap stone. $297.28
Geojute Soil Enrichment Systems.
- 1 roll Antiwash Geojute. $122.13
Spikes 50 lb of 12 inch ardox. $30.00
Tim Hortons Delivery of coffee and donuts to volunteers. $56.25
Fertilizer/Seed Fertilizer and grass seed to repair the
lawn and complete site. $40.00
Topsoil For repairs to lawn. $250.00
Rental of Lawn Rollers For repairs to lawn. $10.00
Totals $3 378.76
Summary
Total Person Hours 343
Total Wages $3 019.20
Total Materials $3 378.76
Total Cost $6 397.96
Site 2
Costs were not available at the time of writing.
13. Biological Assessment
Site 1
There were no pre-construction or post-construction biological assessments of this site.
Site 2
Biomass surveys were conducted at two sites on Black Ash Creek. A 75 m long treatment station was run immediately downstream of the rehabilitation site (Figures 2-3). The 1992 data (prior to rehab.) revealed a population of 1 young-of-the-year (YOY) rainbow trout (at 95% conf. interval 1 +/- 0.004). In 1993 the YOY rainbow trout estimate for that same station was 23 (interval 20-27) and in 1994 was 43 (interval 40-46). This is being called a statistically significant increase in YOY rainbow trout production. If confidence intervals for the population estimates did not overlap, they were considered statistically different. Fish community information is displayed in the attached graphs. Other fish species also increased in number or remained constant. The only exception to this is common shiners, which decreased in 1994.
At the control station ot Osler Bluff Road (Figures 4-5) fish populations either decreased or remained constant. The 1994 exceptions to this are for fathead minnow and mottled sculpin. The YOY rainbow trout numbers are misleading in a graph form because the confidence intervals overlapped for all 3 sampled years. In 1992 the estimate was 227 (interval 135-319), 1993 was 181 (interval 165-198), and in 1994 was 133 (interval 130-136). Statistically it would be difficult to prove a change in numbers.
14. Measures of Success
Site 1
The streambank at this location is completely vegetated. Erosion has been reduced to insignificant. The cribwall successfully weathered the spring flows, which often saw the structure completely submerged. Growth from the cuttings has been vigourous, with Salix eriocephala becoming the dominant willow.
Success Rating: 5
Site 2
This site has also been stabilized. The fascines are growing well, and the slope is vegetated. The stream habitat is stable, with the retaining wall providing a deep, stable undercut pool. Population estimates of rainbow trout YOY are on the increase, and are expected to continue to increase.
Success Rating: 5
15. Key References
Collingwood Harbour Remedial Action Plan Stage 2 Report: A Strategy for restoring the Collingwood Harbour Ecosystem and Delisting Collingwood Harbour as an Area of Concern.1992. Prepared by the Collingwood harbour RAP team, in consultation with the Public Advisory Committee.
Dobbs, F., and Grillmayer, R. 1994. Black Ash Creek Rehabilitation Project Implementation Report. ISBN 0-7778-2696-8. 86p.
Sotir, R., and Gray, D.H. 1989. Fill Slope Repair Using Soil Bioengineering Systems. In Public Works, December 1989.
Correct citation for this contribution:
Grillmayer, R. 1995. Soil bioengineering for streambank protection and fish habitat enhancement, p. 82-98. In J.R.M. Kelso and J.H. Hartig [editors]. Methods of modifying habitat to benefit the Great Lakes ecosystem. CISTI (Can. Inst. Sci. Tech. Inf.) Occas. Pap. No. 1.