Khyex – Tyee: Fish Habitat Works

In 1988, under the direction of Fisheries and Oceans Canada (DFO), an agreement was approved and given to MoT to carry out fish habitat compensation works after the reconstruction of Highway 16, east of Prince Rupert. This work was conducted at five sites along the Skeena River to compensate for riparian vegetation loss. Since 1994, there has been an increase in vegetation at four of the five study sites. The reasons for the success are attributed to transplant operations, the natural recolonization of the vegetation, and the stability of the sites in the fluvial environment. By 2003, the project is expected to reach a “No Net Loss” and eventually, there will be a “Net Gain” in vegetative habitat.

The Khyex-Tyee Fish Habitat Compensation Project began in 1988 when a stretch of Highway 16, located east of Prince Rupert, was upgraded. This roadway was within the tidal portion of the Skeena River estuary between Khyex Bridge and Tyee Bank. The highway in this area was located at the base of a steep bedrock valley wall. The adjacent estuary consisted of mudflat with a fringe of rush and vegetation sedge (mainly Lyngbyeii’s sedge) along the upper intertidal edge. The highway was straightened and widened, and a section of it was relocated to ensure safe distance from a hydro tower. Approval to carry out the widening project was given to MoT by DFO after an agreement was made on a habitat compensation plan. During construction there was extensive infilling of intertidal mudflat and sedge habitat resulting in widespread inter-tidal vegetation loss, affecting a total area of 20,900m2. Further vegetation loss after the construction impact resulted from the poor survival of overwintering shoots and sediment deposition.

The Ministry of Transportation (MoT) established a vegetation compensation and monitoring program to replace the inter-tidal vegetation loss. Areas of primary concern were the Compensation Site, the East Marsh, the West Marsh, the Boat Ramp Marsh and the Donor Marsh. The main strategy for replacing habitat was to construct a series of “spur dikes” along the river to capture sediments and to create suitable conditions for revegetation. The transplants were merely one strategy to increase the revegetation on these sites, as there was a great deal of mudflat area affected. The case study details the actions taken towards achieving a “No Net Loss” in riparian vegetation growth at the five habitat locations.

The objectives of the habitat compensation and monitoring plan were to create foreshore fish habitat compensation works as part of the Highway 16 reconstruction project. To fulfill this objective, MoT was required to:

1) Assess the state of the fish habitat compensation works on the foreshore of the Skeena River after the reconstruction of Highway 16.

2) Offset habitat loss by increasing vegetation growth where there was sediment encroaching onto mudflats.

3) Re-design a compensation habitat that would offset the 20,900m2 in riparian vegetation loss.

4) Achieve a “Net Gain” in intertidal vegetation along the foreshore habitat in 2003.

To ensure that the vegetation growth is stabilizing and to prevent the future loss of foreshore habitat at the five sites along the Skeena River.

Planning and Basic Strategy

The Ministry of Transportation identified three causes for the loss of inter-tidal vegetation: 1) marsh burial from the reconstruction of Highway 16; 2) changing elevations of the land; and 3) sediment accumulation occurring from the compensation works.

In the pre-construction phase, the Ministry selected five compensation sites with the goal of achieving a “No Net Loss” status in riparian vegetation growth. A detailed compensation strategy was created by MoT and was presented for approval to DFO to compensate for the losses from highway reconstruction.

During habitat construction, rock spurs were created to elevate the substrate so successful plant growth could occur. The Ministry also transplanted sedge vegetation at the higher elevations within the compensation sites. The actual foreshore habitat compensation works built differed from the initial designs due to unforeseen contractual, timing, and materials problems.

In the post construction phase, ongoing monitoring programs were implemented to assess habitat losses and gains. Site reviews were conducted in 1990, 1994, 1997 and 1999. Further monitoring is planned in 2003 to observe the long-term effects on plant establishment and substrate stability in the riparian habitat.

PRE-CONSTRUCTION

In 1987, prior to the foreshore habitat construction, a detailed compensation strategy was presented to DFO to create 48,818m2 in new habitat. The initial hydrologic design works for this project included developing a detailed fish habitat compensation strategy and transplanting vegetation to higher ground within the compensation site. The compensation habitat had the potential to return a “Net Gain” of 3:1 in vegetation if the substrate remained at appropriate elevations to support plant growth.

The objective of the compensation plan was to achieve “No Net Loss” in fish habitat and the surrounding vegetation. The plan reduced the temporary impacts of construction to the surrounding habitat and enhanced the potential for long term ‘natural’ marsh expansion through increased sedimentation. This site was expected to take several years to stabilize.

The initial concept entailed elevating the foreshore at three areas: the East Marsh, the West Marsh, and the Boat Ramp Marsh. The final substrate elevations would be similar to those of nearby natural marshes. It was recognized that substrate stability was critical to the successful re-establishment of riparian vegetation. After the areas had been stabilized they would be re-planted with vegetation material from nearby marshes. The transplant operation included planting plugs into plots at the ideal elevation. Full habitat assessments to monitor growth were conducted in 1989, 1990, 1991, 1994, 1996 and 1999.

The main strategy of the Compensation Habitat design was the construction of the spur dikes on the compensation site. This strategy was quite different from actually constructing transplant areas. The spurs excellerated the natural sedimentation process allowing for more tidal marsh to be created.

CONSTRUCTION

MoT developed a strategy to include vegetation transplants that would compensate for the loss in fish and vegetation habitat. When the compensation sites were found to be stable for at least one year, they were re-established with riparian vegetation. Vegetation establishments were at risk until the site had stabilized. These efforts were confined to higher elevations within the foreshore compensation sites.

To minimize fluvial flow along the shoreline, three sites were modified with rockspurs to minimize habitat impacts and to maximize natural sedimentation. The rockspurs were constructed and were completed in September, 1988 and July, 1989. Long straight rockspurs were built perpendicular to the shore at three foreshore sites: the East Marsh, the West Marsh, and the Boat Ramp Marsh. The surface elevation of these rock spurs corresponded to the elevations found in nearby low marsh areas. Inspections of the rockspurs were conducted to see if they showed any signs of erosional damage or if they have developed scour holes at the spur tips. All the work was conducted during low tides so no equipment was used in the river and therefore there was no disruption to fish passage.

The rockspurs were created from rock blasted at Inver quarry and were constructed at an elevation suitable for plant growth. The rockspurs were capped with waste organic material salvaged from the West Marsh. In July 1989, two methods were used to increase vegetation growth on the rockspurs: 1) a seed mix designed for inter-tidal growth and 2) vegetation was taken from Inver Creek, Antigonish Creek and Ekumsekum Creek and transplanted by a highway survey crew.

An environmental contractor and a MoT survey crew of four individuals completed the first sedge transplant operation in the spring of 1989. Donor plant material of three plug sizes was planted in five plots within the foreshore compensation site. Survival and growth data were collected in July 1989. Sedge plugs were taken from the undisturbed Donor Marsh, upstream from the compensation site. The vegetation consisted of predominantly spike-rush and Lyngbyeii’s sedge. The donor material was transplanted to plots of similar elevations at the compensation site using a modified golf course cup cutter and shovels. Four rows of each plug type were planted and each plot contained a total of 72 plugs (White, 1999).

To minimize the risk of transplant failure from sedimentation accretion and erosion in the compensation site, information was gathered from the pilot program in 1989 to maximize vegetation establishment in the 1990 transplant operations.

POST-CONSTRUCTION / MONITORING RESULTS

INITIAL REVIEW

In 1987, prior to construction, the affected foreshore area was 37,764m2. In 1989, initially after the reconstruction of Highway 16 there were 20,900m2 in unavoidable vegetation losses. The undisturbed area covered by foreshore vegetation was 16,864m2. The Compensation Site covered an area of 5,357m2; the East Marsh 1,440m2; the West Marsh 5,189m2; the Boat Ramp 0m2; and the Donor Marsh 4,878m2 (White, 1999).

The post-construction monitoring program of the Khyex-Tyee foreshore habitat was conducted to compare vegetation gains or losses at the five study sites: the Compensation Site, the East Marsh, the West Marsh, the Boat Ramp, and the Donor Marsh. A MoT survey crew recorded surface elevations, expansion rates and plant growth at each location. Surface elevations of the rockspurs and the inter-tidal vegetated areas were measured with a total station. Data reduction followed by computations of the reduced data for cross-section elevations was conducted by MoT.

Photographs and surveys from established cross-sections of the compensation site were documented during construction. The sites will continue to be surveyed periodically for vegetation growth and ground stability.

The compensation site survey data was used to compile contour maps of the East Marsh, the West Marsh and the Boat Ramp to indicate changes in site elevations. These areas were monitored for at least one year to assess their stability.

The expansion rates for the inter-tidal vegetation in the area were compared with digital maps in 1991, 1994, 1996 and 1999. Stem density and shoot lengths were assessed within a quadrat to determine plant growth. This enabled estimates to be made where inter-tidal vegetation was likely to expand. Then plant growth was also evaluated with field observations and photographs.

SIX YEAR REVIEW

In 1994, it was found that less than half of the vegetation from the 1989 and 1990 transplantations were surviving (White, 1999). Sediment deposition, unstable substrates and the poor survival of overwintering shoots caused many of the losses in the foreshore vegetation.

Changes in the total area of foreshore vegetation losses were determined by comparing a pre-construction survey from July, 1989 with a post-construction survey in July, 1994. The area covered by foreshore vegetation in 1994 was 13,733m2. A post-construction survey indicated the net gains in the Compensation site 4,139m2; the East Marsh 743m2; the West Marsh 3,772m2; the Boat Ramp 0m2; and the Donor Marsh were 5,094m2. The area of riparian vegetation loss amounted to 24,031m2 (White, 1999).

ELEVEN YEAR REVIEW

An 11 year review was undertaken to monitor how the habitat compensation sites and their productivity have changed or evolved over time. There was a “Net Gain” in four of the five habitat development areas. In 1999, the area covered by foreshore vegetation was 22,365m2. A post construction survey indicated the net gains in the Compensation Site 10,101m2; the East Marsh 1,920m2; the Boat Ramp Site 47m2; and the Donor Marsh were 5,893m2. The West Marsh still had a vegetation loss of 785m2 and has not yet recovered fully from the impacts of road construction. Vegetation in the West Marsh covers an area of 4,404m2. The total area of riparian vegetation loss amounted to 15,399m2 (White, 1999).

Since 1994, there have been 50 to 80 centimeters in sediment deposition and accumulation along the foreshore resulting from the effects of the rockspurs. Although, the immediate effects of sedimentation such as burial are negative, there are positive long-term ramifications. New foreshore vegetation colonies have established themselves as the habitat has built itself up to elevations compatible for plant growth.

The rates of substrate elevation changes for the compensation sites are slowing down and vegetation colonies are continuing to expand. Vegetation expansion rates were 1.24 to 6.28 during the 1993 to 1996 period. There were very high rates of expansion during this period as the numbers of plant colonies were very small. In comparison, the expansion rates from 1996 to 1999 were constant ranging from 1.39 and 1.98, with one site of contraction, the West Marsh, at 0.64.

From 1991 to 1999, the Compensation Site, the East Marsh, the Donor Marsh, and to a lesser extent, the Boat Ramp have had increases in vegetation growth. The vegetation found on the channelized creek banks was similar to nearby riparian areas and to that which was documented in 1987. There was a large amount of mudflat habitat created by the spur dikes. The work was successful in replacing mudflat. The Donor Marsh had a “Net Gain” in vegetation since the onset of construction. As of 1996, vegetation began to recover dramatically from post construction works at the Compensation Site and the East Marsh where a “Net Gain” had been established. It took seven years for the inter-tidal vegetation to recover from the impacts due to the compensation works, over and above the direct impacts of highway construction. Vegetation productivity on the Compensation Site is better than the Donor Marsh as a result of the 1989 and 1990 transplants and natural regeneration.

The West Marsh had the least amount of vegetation growth as it had a rockier substrate and was subject to greater wave action. The western side of the West Marsh was protected from the southwesterly wind by the 1024+65 rock spur. This side of the marsh has been stable since 1996 and was well established with vegetation. The eastern side of the West Marsh was prevented from establishing vegetation growth due to the instability of the substrate and its susceptibility from wind and water. This side has not yet recovered from the impacts of the compensation efforts at this time and the situation may not improve if present trends continue. Currently, the area is devoid of vegetation as the land has moved up and down 20 centimeters since the construction of the rock spur in 1989. In 1999, it was found that the sediment at the 1019+00 rock spur on the eastern side of the West Marsh stabilized and was at an appropriate elevation for plant growth to expand.

Despite the vegetation losses, the long-term prognosis for plant growth and marsh establishment on this site was good provided that: 1) the transplanted vegetation that is surviving is growing well; 2) the annual rate of change of the surface elevation appears to be approaching the range at which it will not be fatal to vegetation; and 3) there is clear evidence that vegetation is establishing naturally on the site and that this vegetation is thriving. The project is clearly into a much longer time frame before the “No Net Loss” situation is achieved than what was anticipated in 1989. It does seem that “No Net Loss” will be achieved and that, ultimately, it is quite possible that significant habitat gains will be realized. It appears that the work has been somewhat successful in replacing mudflat in that it is nearly at a 1:1 value.

In 1999, the habitat foreshore still had an overall “Net Loss”. The vegetation on the Compensation Site covers only 59% of that prior to construction. There was still a deficit of 15,399m2 in inter-tidal vegetation. The long-term prognosis is excellent for the inter-tidal vegetation within the compensation sites. All the inter-tidal vegetation within the site was growing well whether it was there prior to the project, transplanted, or naturally established after construction (White, 1999). The rate of change of the surface elevation was slowing. With surface stability, vegetation losses from sedimentation will be minimal and inter-tidal growth from existing colonies and new plant colonies are likely to expand. The foreshore habitat is expected to reach “No Net Loss” status in 2003, 15 years after the onset of construction.

There is justification to be optimistic of the future success of the foreshore vegetation between Khyex Bridge and Tyee Bank. However, vegetation loss is still a threat at the Compensation Site and the Donor Marsh due to their susceptibility to the encroaching mudflats. In order to ensure vegetation productivity along the foreshore, site evaluations are recommended in 2003 and 2008 to document growth and to establish long-term results of compensation efforts within this project.

Fisheries and Oceans Canada
Tom Pendray, RP Bio
Habitat Biologist
Box 578
Smithers, BC Canada
V0J 2N0
Phone: (250) 847-7909
Fax: (250) 847-4723
Email: pendrayt@pac.dfo-mpo.gc.caMinistry of Transportation
Environmental Services, Engineering Branch
Angela Buckingham
Manager, Environment
940 Blanshard Street
Victoria, BC Canada
V8W 9T5
Phone: (250) 387-7766
Email: Angela.Buckingham@gems9.gov.bc.ca