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Streams
and Watersheds - Both Upstream and
Downstream Changes May Occur
Finally, it
is worth repeating that any stream or stream reach is part of a
larger watershed.
While we often
think of effects as occurring downstream from a specific event or
situation, influences may be felt upstream as well.
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Figure
1-14
Straightening a portion of this stream has resulted
in a highly unstable system upstream as well as downstream. |
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For
example:
In Fergus County,
MT, straightening part of Cottonwood Creek to reduce the possibility
of erosion of a road changed the character of the stream. The increased
rate of flow in the shortened channel resulted in a headcut (downcutting)
that has moved more than a mile upstream. Having cut four to five
feet down, the channel then began cutting laterally into fine-grained
soils below the level of effective root protection.
Unfortunately,
the result has been the loss of acres of pastureland upstream of
the initial disturbance.
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