The Effectiveness of Bank

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The Effectiveness of Bank Stabilization
Techniques for Reducing Erosion
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Initiated in 1996 by ARCO Environmental
Remediation, L.L.C. (AERL) and the Riparian and
Wetland Research Program (RWRP) at the University
of Montana.
Paul Hansen, Donna DeFrancesco, Stephen Clayton,
Patricia Hettick, Timothy Weisenberger, Brendan
Moynahan, and Ken Miller
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UPPER CLARK FORK RIVERMONTANA
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Typical bank segment of the Clark Fork River
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Objective
To evaluate the effectiveness of various
streambank stabilization techniques for reducing
bank erosion on the upper Clark Fork River.


Focus on bioengineering and the use of native
riparian vegetation instead of traditional
hard treatments such as riprap.
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Study areas
5,708 ft treated and monitored 21 different bank
stabilization treatments 24 treatment areas
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Treatment elements

• Vegetative plantings
• Log barbs,
• Root wads,
• Douglas fir revetments
• Coir fascines
• Rock barbs
• Sod mats
• Rocky Mountain juniper revetments
• Willow/red-osier dogwood fascines
• Layered and non-layered coir (coconut husk)
  fabric

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Treatment elements
Vegetative plantings

• Container vegetation
• Willow cuttings
• Mature willow transplants

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Treatment Combinations Installed
Fall 1996 Spring 1997 Summer 1997 Fall 1998
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9,505 ft monitored as controls 7 control reaches
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Representative control reach
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Field Methods
Channel cross-sections
Surface volume measurements
Vegetation survival
Treatment cost analyses
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Measured 140 permanent cross-sections
Post-ice flow Post peak flow
1996 1997 1998
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General cross-sectional results
All treatments experienced a higher rate of
erosion as a result of the 1997 peak flow event
than due to the 1998 peak flow event or the 1997
or 1998 ice events.
There was no significant lateral erosion as
result of ice events in either 1997 or 1998.
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Rate of bank erosion 1996-1998
Reference reach -0.02 ft/yr
Control reaches -1.1 ft/yr (-5.9
to 0.5)
Treatment reaches -1.5 ft/yr
(-4.6 to 0.8)
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Treatment Reach Volumetric Changes
Losing Treatments lateral erosion
Container plantings -5.9 Juniper
revetments/willow stakes -3.7 Coir
fabric/willow poles -2.1 Coir
fascine/container plants -1.8 Container
plantings -1.8 Coir fabric/willow
poles/log barbs -1.6
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Container plantings treatment 1997
1998
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Gaining/Static Treatment
(ft/yr) Coir fabric/rock barbs/rock
toe/container plants 0.1 Coir
fabric/coir fascine/container plants
0 Coir fabric/willow-dogwood fascine
toe/ container plantings
0 Coir fabric/willow poles 0.5
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(pre-construction)
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8/1997
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5/1998
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Surface profiles
Volumetric analysis of treatment and control
areas Utilizes electronic surveying tools and
GIS capabilitie (ArcInfo, ArcView, and Spatial
Analyst) Used to detect change in volume of
eroding bank over time First completed in this
study in 1998
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100 bank surface profiles (13,000 ft of
riverbank) monitored with an electronic total
station
March 1998
August 1998
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Depiction of X,Y, and Z riverbank coordinates
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Bank visually constructed using Spatial Analyst
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Before construction
After construction
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Before treatment
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Change in volume after treatment 529 cu yds
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Riverbank volume changes 1998
Reference reach 3 cu yds 0.14cu
yds/sq yd
Control reaches -56 cu yds average
-0.13 cu yds/sq yd (6) (-402 to 162
cu yds)
Treatment reaches -4 cu yds average
-0.03 cu yds/sq yd (14) (-117 to 98
cu yds)
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Treatment Reach Volumetric Changes
Losing Treatments Overall volume
vol/area Container plantings -59 cu
yds -0.30 Mat. transplants/ willow stakes
-117 cu yds -0.26 Coir fascine/container plants
-64 cu yds -0.17 Coir fabric/willow
poles/log barbs -36 cu yds -0.15 Rock
barbs/mat. transplants -16 cu yds -0.05
Cr. fabric/cr fascine/cntainr plants -14 cu
yds -0.04 Coir fabric/willow poles -39
cu yds -0.02
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Treatment Reach Volumetric Changes
Gaining Treatments Overall volume
vol/area Douglas fir revetments/willow
stakes 98 cu yds 0.53 Juniper
revets/willow stakes 67 cu
yds 0.15 Coir fabric and willow poles
53 cu yds 0.14 Cr. fabric/rock barbs/rock
toe/contner plants 23cu yds 0.05 Cr.
Fabric/willow-dogwood fascine/container
plants 13 cu yds 0.04 Root
wads/mat. transplants/container plants 26 cu
yds 0.03 Container plantings
3 cu yds 0.02
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Revetment treatment Downstream end of
treatment (-45 cu yds) Upstream end of
treatment (72 cu yds)
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Some Conclusions
There was little lateral erosion attributed to
ice events in either 1997 or 1998. Majority of
erosion is attributed to peak flow events. Peak
flow in 1997 caused signifcantly more erosion
than 1998.
As expected, all treatments where vegetation was
planted on the terrace away from the immediate
bank (as in container plantings alone) and the
bank was not adjusted (e.g. sloped), the bank
continued to erode.
Each cross section of bank is affected by varying
factors that contribute to its rate of erosion.
Therefore, it may not be appropriate to directly
compare control areas to treatment
areas. However, it may be more appropriate to
compare treatment banks to the same bank at
pretreatment levels of erosion.