Introduction to Stream Restoration - Hydro-Environmental Analysis: Freshwater Environments - page 229

FIGURE 8.15 Dry dredge operation in backwater restoration of the Illinois River. (From Marlin, J.C.,
Potential Use of Innovative Dredge Technology and Beneicial Use of Sediment for River Restoration , Waste
Management and Research Center, Illinois Department of Natural Resources, Champaign, IL, 2001.)
than mechanical dredging. Dry dredges (high solids dredges; Figure 8.15) lift sediment from the
bottom and use a displacement pump to move it without adding water.
8.4.3 b ank or c HanneL r eSHapInG
Bank or channel reshaping is a component of channel reconiguration or alignment and loodplain
reconnection activities. The reshaping is intended to reintroduce or create a stable coniguration,
such as in channels that are incised and/or eroding, straightened (channelized), over wide, or have a
loss of loodplain function or connection. Channel reshaping may also be necessary for the creation
or maintenance of riparian buffers.
One case for channel reshaping is for incising channels. Deeply incised channels are often
unstable, with accelerated bank erosion, land loss, aquatic habitat loss, lower water tables, reduced
land productivity, and accelerated downstream sedimentation. In addition, in an incised condition,
the river may have lost access to the loodplain and is therefore no longer receiving the beneits
from overbank looding. Riprap is commonly used to reduce the consequences of channel inci-
sion. However, riprap generally results in negative values for ish and wildlife. An alternative may
be to excavate and construct a new loodplain at the incised channel elevation or higher (but not at
the original level), which is a proactive acceleration of the natural progression of incised channels.
Where reach alterations are the primary cause of incision, another alternative would be to restore
the historic channel grade and elevation to reestablish a connection with the loodplain by raising
the channel bed or moving the channel to a new or former location on the old loodplain surface
(Saldi-Caromile et al. 2004).
Channel or bank reshaping is also an intervention method for over-widened rivers, which are
common in western states in low-depleted streams due to a reduction in the stream power and an
increase in sedimentation and consequently bank erosion. Reshaping usually requires the use of
heavy equipment and is usually a very publicly visible restoration methodology. Reshaping is also
commonly completed in conjunction with other structural measures to restore and maintain stream
stability, as described by Rosgen (1997).
8.4.4 b ouLderS a dded
The addition of boulders is a commonly used method of enhancing instream habitats. The pools
and eddies around the boulders create ish habitats and the boulder surface is important to clinging
invertebrates, periphyton, and other organisms.