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Pool Cover Habitat

is Important !

 

    In the pool habitat design, both engineered undercut banks and willow planting was used to provide good cover habitat for trout. The engineered undercut banks were constructed using timber frame construction and additional woody debris was also used to insure that refuge for all year classes of trout would be available.

    Willow and tree live stakes were pre-rooted and planted around the perimeter of the pools after they had been constructed, so that in future years the added shade and cover would be attractive to resident trout. The root systems of these plants would also help stabilize the banks around the pools over time.

    There was no rock present when the pools were excavated, so a mix of cobble and boulders was added to the bottom of all of the pools. This measure would enhance the invertebrate habitat and populations in the stream and provide an added food base for resident trout.

    The larger cobble and rock will also provide added cover for both juvenile and adult trout that make the pools their home!

        Pool Habitats on Millennium Creek

    Pool habitats on both large and small streams are vital environments in which trout live throughout the year! In the open water seasons, the deep pool habitats provide both security and space for all life stages of resident trout populations. In the winter months, when the ice covers the shallow areas of a stream, trout retreat to these deep pools to live out the winter season, below a covering of snow and ice.

    The pool habitats built on Millennium Creek were constructed with undercut banks and cover habitat consisting of woody debris and boulders. The primary objective when constructing these habitats is too emulate a natural occurring and self maintaining deep pool that is hard to distinguish as being man-made.

Above Photo:

 

    The overall gradient on Millennium Creek is very low. In order to effectively maintain pool depths after construction, a low profile log v-weir design was necessary for keeping the pool habitats clean.

    The v-weir structures concentrate the flow into a core velocity that scours deep into the pool depths, with very minimal drop.

 

Using a Flow By-pass Pipe

 

  To minimize the impacts of silt loading downstream of a construction site, a flow by-pass pipe is used to isolate the work area, during pool excavation. The flange secured to the upstream end of the pipe dams off the channel and results in the entire volume of flow being passed thru the corrugated plastic pipe. Sand bags are used to achieve this goal and they are also used to dam around the discharge end of the pipe.

    There is a roughness factor which slows the velocity of flow in the pipe, which helps minimize the effects of erosion on the downstream end. The 10 inch pipe in the photo to the left weighs in at approximately 15 kg., so it is easily moved by hand to the various pool sites.

    A number of silt fences were installed downstream of the construction area, so that any sediment created while installing the flow by-pass or v-weir, would be trapped at the fence site. There were two silt trap pools created on two of the silt fence sites, to handle the collection of silt over time. These silt trap pools were cleaned out as required, using the flow by-pass to accomplish the task.

    All of the spoil and silt that was removed from the creek, was hauled to an isolated area and then trucked to a disposal site on a number of occasions during the entire restoration project. Approximately 58 cubic metres of spoil was hauled away from the isolation site, during the 3 year enhancement program.

Above: A flow by-pass pipe is placed into the stream channel to isolate the work area and allow clean water to be diverted around the pool excavation site.

Above Photos: Two log v-weirs that were constructed on Millennium Creek in 2007. Photos taken in the summer of 2010.

Millennium Creek Pool Habitats                        Important Seasonal Habitats for Trout !

Deflectors are a great stream training design to help constrict flow and deepen a stream channel!

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