11/10/2012

Ayum Creek Habitat Restoration - Salmon And Large Woody Debris


Large Woody Debris put in place during Ayum Creek stream restoration

Ayum Creek is a good salmon stream, and like all good salmon habitat, it contains the trunks of large trees. In the creek assessment world these large trees are known as LWD, or Large Woody Debris, and their contribution to salmon streams is significant. The structure they provide is critical to the chum, coho, stealhead and trout that call Ayum creek home.

In less than 100 years of industrial logging in British Columbia, the majority of salmon-bearing coastal waterways went from pristine to extinct, threatened, or uncertain status. Prior to 1988, coastal streams were clear cut logged right to their banks. This starved the streams of the large, mature fallen trees (LWD) which are the primary structuring element in the habitat.

Once affected, degraded waterways can take decades or centuries to recover naturally. It would take about 100 - 200 years alone for the trees to grow large enough for what is required in a maximally functioning salmon stream. That is why stream rehabilitation projects often bring in mature trees (in the form of large logs) from elsewhere, and place them in strategic locations.


This LWD complex is anchored into the bank of lower Ayum Creek, and creates a deep, stable
pool that benefits spawning and juvenile chum and coho salmon

The loss of the large old-growth trees in stream channels with their massive rootwads as anchors, is the type of structure that cannot be easily duplicated in degraded riparian areas. It is the roots of fallen old growth trees that anchor the trees in place against the pressure of swollen winter waters. This is why cables anchoring woody complexes to streamside trees and instream boulders are used in restoration projects in leu of roots. 

The role wood played in providing the structures that salmon need was not established until the 1980s. At that time old growth trees and fallen LWD complexes were found to be of primary importance in, and along, salmon streams. They create structures that result in stable stream banks, deep pools of still water, and places for juvenile fish to hide from predators.

Bridge over Ayum Creek on the Galloping Goose Trail, looking west toward Sooke
Logging had other impacts including increased erosion, road failures, and landslides, all of which increase the sedimentation of salmon streams. Culverts blocked the free flow of fish, and wood was removed from streams as routine practice.

Ayum Creek was affected by development and industrial activity from the earliest days of Sooke. On the land logging was a mainstay of the community, and on the water the salmon fishery was heavily exploited. The Ayum Creek watershed had been used for thousands of years by the T'Sou-ke 1st Nations, but now just a few decades after colonization and industrialization, it had become degraded like so many other coastal waters. The salmon run was in peril.

Now much of the Ayum Creek watershed lies in protected regional park reserves. Their mandate focuses on preservation and enhancement of the natural environment of mixed forest and a biologically rich estuary.

Part of the enhancements over the years have included watershed restoration projects, one of which has been the placement of LWD complexes in the creek to mimic the structure of fallen old growth trees that used to grow along the banks.

Something must be working, because there are some nice salmon returning to Ayum Creek every year, including the 2012 run.

Not only do the trees benefit the salmon, but the opposite is true as well. The nutrients that the salmon provide to the stream environment will enhance the growth of the nearby forest, ensuring future LWD for the fish. Those same nutrients are also important for the growth and survival of juvenile salmon.

Bigleaf maple leaves fall on Ayum Creek Bridge
In 1994 British Columbia implemented the Watershed Restoration Program to reverse habitat losses associated with past and new forest harvesting. This program helps to accelerate the restoration of affected watersheds, but will do little if not accompanied by making waterways off limits to future logging in perpetuity.

Watershed protection is the preferred, cost effective choice over watershed rehabilitation. It is just one more reason to protect our old growth forests, as well as the second growth forests that now dominate most coastal watersheds. Intact watersheds provide services that result in excellent water quality and habitat for salmon and many other living things.

Including humans.

Getting There

From Victoria, take the Old Island Highway/Highway 14/Sooke Road toward Sooke. Just before town look for Ludlow Road on your right. Turn here to hike to the bridge, or continue past Ludlow to turn left off the highway to park and hike to Sooke Basin via the forest trails.

Ayum Creek Regional Park Reserve currently has no services as nature preservation is the key here. There are several trails between Highway 14 and Sooke Basin, and the Galloping Goose Trail crosses a section of the park north of the highway.

Some of the lower Ayum Creek salmon habitat restoration can be viewed from the bridge on the Galloping Goose Trail where it crosses the creek. Looking toward Sooke Basin one can see both the LWD complex put in place, as well as the huge fish that hang out in the pool it created.

Limited parking is available on Ludlow Road, then walk west towards Sooke along the Galloping Goose to get to the bridge. To hike the lower creek to Sooke Basin, park on the south side of Highway 14 along the edge of the park reserve.


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