Coquihalla River (Ladner Creek) Side Channel Habitat Restoration


Year 2008
Proponent British Columbia Conservation Foundation
Project type Habitat
FSWP funding source DFO Fraser Basin Initiative
Grant amount $20,000
Total project value $60,900
Other project funders

Ministry of Environment
HCTF
Ministry of Transportation
BC Conservation Corps

ID number 08 HPR D107

Location: Cariboo-Chilcotin, Hope, BC

Project Summary

Purpose:
This proposal is for funding to construct stable off-channel habitat on Ladner Creek a tributary of the Coquihalla River.  The Coquihalla River flows south-westerly from its origin in the Cascade Mountains and enters the Fraser River near the town of Hope, approximately 150 km east of Vancouver.  The Coquihalla Highway follows the river from Hope to its confluence with Boston Bar Creek, a tributary which enters the river upstream of Ladner Creek.  The Coquihalla River contains one of only 2 native summer run steelhead populations in the lower Fraser River.  Historic snorkel counts of summer steelhead have been as high as 1000 fish (Caverly, 1977; Ptolemy, 1989) while in the last five years no count has been over 250 fish, with a low of 97 adults counted in 2007.

The Coquihalla watershed has been heavily affected by human activities.  The first sawmill was built in 1958 and marked the beginning of logging activities in the area.  Completed in 1916, the Kettle Valley Railway helped open the Coquihalla Valley to extensive logging activity, which continues to this day.  In 1953, an oil pipeline was laid through the valley, followed in 1957 by a natural gas pipeline, which was expanded in 1979.  In 1979, construction began on the four-lane Coquihalla Highway, which was completed in 1986.  Due to human influence, stable off-channel habitat is sparse in the Coquihalla watershed.  One goal of this project will be creation of off channel habitat in Ladner Creek that will improve summer rearing and over winter refuge habitat for the upper Coquihalla watershed.  The ultimate goal of rehabilitating the Coquihalla watershed is to maintain and protect this valuable wild summer run steelhead population and in doing so, improve local angling opportunities. 

Despite human impacts, observations show Ladner Creek supports juvenile trout and possibly char.  Substantial growth of diatomaceous algae suggests a high nutrient content (possibly due to minerals in the rock exposed after past mining operations) compared to a relatively low nutrient content in the Coquihalla mainstem.  Following a field investigation (partially funded by FSWP), a professional biologist and a professional engineer, on contract to the BC Conservation Foundation, identified the proposed channel location as a suitable site for development.  The channel has been designed with a protected semi-natural intake to allow periodic controlled flushing flows.  Complex fish habitat will be added in the form of large wood and boulder riffles, in the second year of the project.  We anticipate improved summer rearing conditions and greater over winter survival ultimately leading to an increase in smolt output.


Method:
A suitable site for a semi-natural intake exists approximately 150 m downstream of a high railway trestle over Ladner Creek.  Slight modification to the Ladner mainstem with large boulders will train a portion of the low flow towards the left bank intake location (figure 1).  A large (5 foot diameter) fallen cedar buried into the bank will act as a sheer log, under which water will enter into the channel.  Based on its coarse surface-exposed materials, excavation will yield a boulder dominated channel.  The channel, which is separated into distinct upper and lower segments, totals ~740 m in length.  This has the potential to be developed as a 1-2 % grade controlled-flow side channel, which could be extended to 800-850 m through channel curvature. The channel will re-enter the Ladner mainstem approximately 110 m upstream from the Coquihalla highway bridge which crosses the creek high above.  Habitat attributes throughout this channel would be constructed in 2009 to improve summer rearing habitat and provide over-winter refuge habitat therefore increasing the survival of juvenile steelhead and char, the two main species present in the upper Coquihalla.

A conventional excavator will be used to construct the intake and create the channel in an area that was once part of the active floodplain, but is now inactive due to channel incision.  Alder trees up to 30 cm in diameter will be removed to create the channel, and then returned later to contribute to habitat complexity.  The first portion of the channel, a length of approximately 450 m, requires the bulk of the excavation.  Excavated material will be side-cast towards the scree slope on the margin of the floodplain.  At the terminus of this portion, the channel re-enters the active floodplain for a length of approximately 50 m. For the proposed works in 2008, the original idea to create a berm to help direct and protect side channel flow to the second portion of the side channel will not be completed.  The reasoning behind the decision to remove this part of the proposed works is strictly budget orientated and spawns from the reduction of proposed project funds. Some excavation can be completed allowing side channel and mainstem Ladner Creek water to re-enter the historic floodplain for a length of up to 350 m with relatively little excavation required.  A significant portion of woody material exists within the historic floodplain that can be added to the channel in 2008 for habitat complexity. Further complex habitat will be added to the channel in 2009 to ensure maximum biological productivity.

In October 2007, a helicopter over-flight of the upper Ladner watershed by BCCF personal indicated relatively stable terrain confirming that this system is suitable for off-channel development.  A conceptual drawing of the intake site modifications and a channel plan has already been completed by a professional engineer.  Following successful acquisition of all permits required to complete this project, active construction will occur within the region’s instream fisheries work window of Aug 15 to Sept 15, 2008. Construction will require 8 to 12 days with an excavator which will include one day to reactivate/create an access route from a tote road that exists after construction of the Coquihalla highway in the early 1980’s.


Outcomes:
a) A semi-natural controlled flow intake capable of flowing year round with little or no maintenance.

b) Stable flood protected off-channel habitat totaling up to 320 m in length and 320 m of unprotected.  Flow targets for both spawner access and advanced parr rearing in spring, mid-summer and late summer-autumn will be 0.57-0.7 m3·sec-1, 0.4 m3·sec-1 and 0.2 m3·sec-1, respectively, or about 20 % of mainstem flows.

c) An approximate total of 3,000 m2 of additional spawning habitat, juvenile rearing habitat and more importantly winter refuge habitat to benefit the adult and juvenile stages of steelhead trout, cutthroat trout and char.