Current through Register Vol. 24-18, September 15, 2024
(1)
Description: The department
discourages channel relocation and realignment and will approve them only when
a person can demonstrate benefits or lack of adverse impact to fish life.
Channel relocation may solve problems of channel encroachment and/or
confinement, and foster the development of a new channel with appropriate
channel morphology and healthy riparian zones. Channel relocation permanently
changes the location of the channel. The new channel should be designed with
bioengineered stability, rather than structural stability, so that the profile,
pattern, cross-section and bed elevation can be expected to achieve long-term
natural functioning. Channel realignment is used to restore a single-thread,
straightened channel(s) to a more natural sinuous pattern.
(2)
Fish life concerns:
(a) Channel relocation and realignment is a
major undertaking involving reconstructing the channel bed, habitat features,
channel banks, and flood plain. In-channel work will have a much greater impact
on the bank and channel than off-channel work including the downstream burial
of invertebrates, elevated suspended solids, and habitat destruction.
(b) However, channel relocation and
realignment can also benefit fish life by altering channel planform, profile,
and cross-section geometry to restore habitat that supports fish life.
Restoration work can range from complete reconstruction of a channel to
smaller-scale alterations that induce incremental changes to channel
form.
(3)
Channel
relocation and realignment design: A channel relocation and realignment
may be approved if:
(a) Permanent new
channels are similar in length, width, depth, flood plain configuration, and
gradient to the old channel(s); and
(b) The new channel(s) incorporates habitat
components, bed materials, channel morphology, and native or other approved
vegetation that provides better protection for fish life than that which
previously existed in the old channel.
(4)
Channel relocation and realignment
construction:
(a) During construction,
a person must isolate the new channel from the flowing watercourse.
(b) Before water is diverted into a permanent
new channel(s), a person must install approved habitat components and bed and
bank protection materials to prevent erosion as specified the approved
design.
(c) When filling the old
channel(s), water discharging from the fill must not adversely affect fish
life.
(d) The angle of the
structure used to divert the water into the new channel(s) must allow a smooth
transition of water flow.
