| INTRODUCTION In August and
September 2002, the
Veins of Life Watershed Society was involved in a project
to enhance the Langford Lake outlet creek in a section adjacent
to the Trans-Canada Highway, near Sooke Lake Road. The creek
was to be deepened and widened to allow for extra flow during
periods of extreme
rainfall.
The goal of the enhancement project was to increase the
flood-levels of the outlet so that Langford Lake would not
flood the surrounding residential properties during future
winter storms. A series of pools
and cutbanks were designed, to allow enough standing water
to remain for fish habitat during normal flow periods.
PARTICIPANTS
The project
was managed by the District of Langford and R. Irwin Consulting
Ltd.; Earth Tech created the blue-prints, the excavation
was done by Don
Mann Excavating Ltd.,
and the environmental restoration work was done by Veins
of Life. |
| Figure
1: The blue star indicates the location of the enhancement
site along the Langford Lake outlet
(Map adapted from Natural Areas Atlas, Capital Regional District)
|
Figure 2: Orthographic
photo of the enhancement area.
(Photo
adapted from Natural Areas Atlas, Capital Regional District)
| METHODOLOGY
A. Planning
Plans were drawn up by Earth-Tech and the environmental
monitor, Chris Morley, assigning the locations of the cut-banks
and pools that would be constructed for fish habitat. Supplies
were gathered together and the Stream Restoration Supervisor
and the Stream Restoration Technician set a game plan for
the work that lay ahead. |
Figures 3
& 4: View of east end of stream before excavation.
| B.
Equipment Used
Cedar logs, boulders, gravel, 3/8"
steel cable and clamps, 1/2" ogger (drill), gas powered
generator and water pump, sandbags, erosion-control fabric
(from Nilex), grass seed, hay bales, shovels, rakes, wheelbarrows.
|
| Figure 5: View of west
end of stream before excavation. |
| C.
Stream Enhancement
Site Preparation
The stream was sandbagged at the south end of the culvert
that passes under the highway, in order to keep the stream-bed
dry while we were working. An excavator began widening and
deepening the stream on August 13, 2002. The machine work
started at the east end of the stream, working towards the
culvert. The operator put some ferns and other vegetation
asside as he excavated the banks, so that we could transplant
them later. An arborist came in to cut down 4 maples that
would be replaced at the end of the stream/bank work.Once
the first 2 pools were completed and the banks were widened,
we were able to begin our work restoring the banks and stream
to a natural state. |
| Figure 6:
Four maples along the stream bank had to be removed during
the widening process. Each maple that was cut down would be
replaced with four new maples. |
Bank Work
Once the excavator had finished digging out the first pool,
we began our work along the banks; creating cutbanks and stabilizing
the disturbed banks with erosion control material.
| Figure
7: After widening the stream, the banks were very unstable. |
1. Cutbanks
To create the cutbanks or "fish-condos", the excavator
cut a notch in the side of the bank and then placed some large
boulders roughly two metres apart. We then placed three cedar
logs on top of the boulders and laced 3/8" steel cable
through our pre-drilled holes to bind the logs together. The
excavator then placed more boulders on top of the logs, as well
as gravel and finally soil, to cover the logs completely, essentially
making them part of the existing bank. Erosion-control mattress
was placed over the soil above the cutbank and seeded with fall-rye
so that the soil would not be flushed back into the stream during
the rainy season. The result is a small covered area at the
side of the stream (cutbank), which will retain standing water
and provide a place for fish to rest during their journey upstream.
| Figures
8-9: A double-cutbank or, "fish-condo" created
to allow sheltered, standing water for fish to rest or spawn. |
2. Erosion Control
After the excavator widened the stream, most of
the banks were left in a very unstable condition. To remedy
this, we placed erosion control mattress over the steep areas
and staked it with live stakes. This mattress was then seeded
with a combination of a fast-growing rye/wheat/vetch seed mix,
and a native seed mix that would fill in later. The combination
of mattress and grass will keep the banks from eroding until
other plants have a chance to establish themselves.
| Figures
10 - 13: Erosion-control mattress (top & middle) was
used on the steep areas of the disturbed banks. Live stakes
were used to attatch the erosion-control mattress to the
bank. The banks were seeded after the mattress was placed. |
3. Rip-Wrap
In some areas, there were large trees in close proximity to
the bank. To protect their roots from erosion, "rip-wrap"
(a collection of large boulders) was added to the bank at the
base of the trees. This rip-wrap essentially adds a protective
barrier over the roots, minimizing erosional damage.
| Figures
14 -15: Rip-wrap (collection of large boulders) was placed
along the bank, at the base of any large trees. |
In-Stream Work
1. Low-Flow Channels
After the excavator finished digging
an area, and he was satisfied with the grade, he laid-down some
river gravel along the bottom. He left a fairly flat surface
which resembled a ditch more than a stream. To make it look
and work more like a stream, we hand-dug a small, 2-3 ft. wide
channel along the center. This would mimic the natural water
course in this stream by creating a "low-flow channel"
for the water to follow.
| Figure
16 - 17: Above, the excavator digs out one of the pools
and places a layer of gravel on the bottom. Below, a low-flow
channel to direct the flow of the stream during low periods. |
2. Boulder Placement
in pools
After the pools were completed, and the
cutbanks were constructed, some large boulders were "strategically"
placed in the pool to create more fish habitat. (See below):
| Figure
18: Large rocks were added to pools for fish habitat. |
3. Digging, Digging and More Digging!
The last section of stream closest to the culvert had to be
dug-out by hand because the area was too tight for the excavator
to get into. A few hundred wheel-barrows of dirt and gravel
later (plus a few well-deserved slurpy breaks)....
| Figure
19: A small area was hand-dug by the mighty restoration
crew! |
4. Washing the Stream
Once all the gravel had been laid-out
by the excavator, the stream needed to be washed. There was
a lot of excess sediment in the gravel that could potentially
flush into Goldstream River during the first heavy rain. We
did not want this to happen.
A truck came in and sprayed the entire
length of the stream. Much of the sediment washed off the top
and settled at the bottom, where it would cement itself. In
particularly dirty areas, we washed the water into the nearest
pool, and filled the pool so we could pump out the silty water.
This process was very successful in removing the majority of
the unwanted sediment.
| Figure 20:
A few sections of stream were pumped to remove sediment.
|
Clean-up of Access Points
The excavator left a few access points
in his travels that we had to clean up and cover so that the
dirt would not erode into the stream. The areas were covered
with hay and then seeded with grass seed to create some stability
in sloping areas which could potentially drain into the stream.
The areas will then be planted (up to 15m from the bank) to
fill in these bear spots and essentially make them "dissappear."
| Figures
21 & 22: The access points left by the excavator needed
to be covered with straw and seeded with grass so they would
not erode into the stream. |
Planting
All of the disturbed areas including banks and
access points were replanted with a variety of native plants
suitable for a riparian (stream-side) environment. Species included:
Broadleaf Maple, Red Alder, Salal, Salmonberry, Ocean Spray,
Red Elderberry, Red Huckleberry, Snowberry, Pacific Ninebark,
Indian Plum, and Sward Fern. A total of 245 plants were placed
in the ground.
Figures 23 & 24: Potted
plants ready and waiting!
Figures 25-27: Planting
in progress along disturbed access points and banks.
| Plants were placed 2 metres apart along the
disturbed areas. Holes were cut into the erosion-control
mattress in order to put plants into the side of the banks. |
Figure 28: Planting, planting...
more planting!
| The fall leaves provided a natural cover
over the banks, meshing in with the grass and erosion-control
mattress to stabilize the disturbed areas. |
| Figure 29: The cutbank
is barely visible now, with fallen leaves and grass covering
the top. |
| All plants were labeled for future monitoring
purposes. |
| Figure
30:Plant label, "VOLWS Oct 02" |
The Crew
|
