Suitable locations
A. Introduction
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Pocket refuge may be improved by simple actions taken in the stream at suitable locations.
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What are those suitable locations?
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They would be where the depth and volume of refuge can be increased efficiently and without adverse result.
Assessing suitable locations for improving pocket refuge
B. Considerations
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Potentially favorable locations for improving refuge would have these stream features:
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Improvable natural pocket
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Confined width
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Higher streambed gradient
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Readily available materials, that is, rocks or wood to add or remove
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Shade
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Deeper main path, or thalweg
2. A possible adverse result would be inadvertently backing up and slowing flow in the channel.
3. Best actions would enable access to refuge during low-flow conditions, hence the value of a deeper main path.
4. Streams can be long and productivity is important, so efficient actions would not duplicate existing, sufficient refuge.
C. Example locations
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Photographs below show locations at 6 streams: Coal, Priest, Roaring Forks, Scotch, Stoner, and Taylor.
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The favorability of features at those locations for actions to improve pocket refute are briefly assessed.
Location 1
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Has an improvable natural pocket, somewhat confined stream width, and available rocks to add for increasing structure height and to remove for deepening the pocket.
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Upstream gradient change is small.
Location 2
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Also has an improvable natural pocket, somewhat confined stream width, and available rocks to add for increasing structure height and to remove for deepening the pocket.
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Upstream gradient change is greater than at Location 1.
Location 3
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Similar favorable features as at Locations 1 and 2, but has a greater gradient change than both.
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Scouring below a structure due to stream water momentum depends on stream velocity and elevation drop. This location would have greater scouring than at the locations described above.
Location 4
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The location is a good example of close-by stream-side shading.
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There is little gradient change at this location, however, and no natural structure inviting efficiency in improvement action. As well, there is no well-defined main path of stream flow that could minimize connectivity problems between pockets during low flow.
Location 5
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Due to the hard-rock streambed, there is no well-defined, deeper path of stream flow. Instead, there is consistently shallow passage of water across the stream width.
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During low flow, a loss of stream connectivity at this location is possible. It is not a good candidate for actions to improve refuge.
Location 6
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Natural pockets appear numerous at this stretch of stream water. The channel is considerably confined and has relatively high streambed gradient.
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A more productive use of time for improving stream water pocket refuge would be made elsewhere.
Location 7
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Beaver activity has created refuge above the dam structure. Trout were observed there.
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As with Location 6, a productive use of time for improving pocket refuge would be made elsewhere.
Location 8
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There is no improvable pocket refuge in this stream stretch, and little elevation change. As well, there is no well-defined, deeper path of flow in the channel.
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The location is not an attractive candidate for efficient efforts to improve refuge.
