Streambank Protection

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Streambank Protection
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Stream Bank Stabilization

• Activities
• Removal of slide debris from the bank, channel,
  or roadway
• Terraces with willow walls or other bioengineered
  solutions
• Crib walls, rip rap, or retaining structures
• Back filling or reshaping the bank
• Re-establishing damaged roadway features
• Repairing or cleaning drainage systems
• Applying erosion controls
• Revegetation

Stream bank stabilization projects are necessary
to repair road related slip outs, washouts, and
slides on roads adjacent to stream channels.
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Stream Bank Stabilization BMPs
In planning a stream bank stabilization project,
it is important to consider bioengineering
alternatives in order to create stream bank
habitat that salmon need to survive.
Bioengineering involves integrating living woody
and herbaceous materials with organic and
inorganic materials to increase the strength and
structure of the soil.

• Observe General BMPs (Riparian and Water Quality)
• When possible, use bioengineering techniques over
  hardscape repairs to create natural stream bank
  environment
• Implement Erosion, Sediment, and Water Management
  BMPs
• Minimize disturbed area by only removing material
  needed to stabilize site and prevent sediment
  delivery to stream system
• Consider downstream effects of stabilization
  project
• If planted, plan for irrigation, maintenance, and
  monitoring

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Upstream Downstream Consequences of Streambank
Failure
Anytime a stream channel is modified through the
addition or removal of a stream component, there
is potential upstream and downstream
consequences. This includes adding or removing
sediment, woody debris, grade control structures,
fish habitat structures, stream crossing
structures, and bank stabilization. When
removing a logjam or woody debris with sediment
stored behind it, a natural resource scientist
should be consulted on potential upstream and
downstream consequences. Often the consequence
of streambank failure can be detrimental to fish
habitat and county or private facilities.
Failed Stream Crossings
Bank Erosion
Photos courtesy of US Forest Service
Loss of Fish Habitat
Photo courtesy of US Forest Service
Photo by Deb Freeman
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• Anytime a stream channel is modified through the
  addition or removal of a stream component, there
  is potential upstream and downstream
  consequences.

This includes adding or removing sediment, woody
debris, grade control structures, fish habitat
structures, stream crossing structures, and bank
stabilization.
Often the consequence can be detrimental to fish
habitat and county or private facilities.
When removing a logjam or woody debris with
sediment stored behind it, a natural resource
scientist should be consulted on potential
upstream and downstream consequences.
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Bioengineering Hardscape
Here is an example of stream bank stabilization
in an urban creek confined by development on
either side. Rock was used to stabilize the
lower section of the bank with trees planted to
stabilize the upper section. A coconut fiber
erosion control blanket was used to prevent
surface erosion.
Incorporate plantings of vegetation into
hardscape design
Attempt to limit hardscape protection to below
the ordinary high water mark
Consult specialist about size, placement, and use
of hardscape materials
Photo by Tyler Ledwith
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Stream Bank Bioengineering
Rock weirs (top right) with willow cuttings were
used to slow water velocities along the bank to
promote sediment deposition and prevent bank
erosion.
Incorporate bioengineering protection with
hardscape design
Willow mats were used to stabilize the bank above
the ordinary high water mark.
An example of bioengineering techniques used to
stabilize a stream bank along a river.
This site had been in place for one year at the
time of the photo.
Incorporate plantings of vegetation into
hardscape design
Attempt to limit hardscape protection to below
the ordinary high water mark
Photo by Tyler Ledwith
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Willow wall revetment for streambank
stabilization, using live willow stakes.
Click on the link for more information on
installing Willow Stakes http//www.urbancreeks.o
rg/Live_Staking_Joint_Planting.pdf
The willow roots will grow into the fill soil,
rebuilding the bank and protecting it from
further erosion.
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Stabilization of reconstructed Guadalupe Riverbed
and banks San Jose, CA
Stabilized banks and bed with erosion blankets
and seed
Condition after six months
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Creek, Drainage Swale and Channel Control BMPs
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Inadequate BMPs will result in discharge of
significant sediment, with associated impacts.
The contractor put too much reliance on one BMP
the silt fence. This discharge could have been
minimized by covering the banks with erosion
control blankets on the slopes.
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This disturbed drainage ditch is a disaster.
The rain event that caused this damage also
dislodged thousands of cubic yards of silt and
sediment into surface waters, and cost hundreds
of thousands of dollars in cleanup costs and
fines.
The damage could have been minimized by using
appropriate Erosion Control BMPs on the slopes,
such as erosion control blankets or hydroseeding.
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Swales and Drainage Ditch Protection

• Protection of disturbed swales and drainage
  ditches are important because of concentrated
  flow, creating high energy and high potential for
  sedimentation discharge.
• Stabilizing with effective erosion control
  measures will minimize such impact. The photo
  shows channel blankets used to stabilize the
  disturbed channel.

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The reason for this success lies in the
implementation of appropriate erosion control
BMPs used to protect the banks, such as channel
blankets.
Even though this is a concentrated high energy
flow, there is very little sedimentation in the
water, and no erosion of the drainage ditch.
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Multiple methods for critical drainage ditch
situations !

• Here, a combination of nylon filament blanket
  (lining the ditch) and fiber rolls were used to
  protect the drainage ditch and the surrounding
  flat lots.

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Swale and drainage ditch protection is especially
critical, because the function of a drainage
ditch is to concentrate flow. This drainage
ditch is protected by straw fiber erosion control
balnkets, and is well designed and maintained.
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An example of well stabilized drainage ditch
using a combination of effective erosion control
blanket and large rock as an energy dissipater.
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Large rock serves as an energy dissipater for
this outlet
Without the rock the run off would flow
unchecked, creating rills and gullies to
transport sediment and damaging the adjacent land.
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Water flow velocity is reduced by using the fiber
rolls in a chevron pattern.
The application of straw mulch protects from
erosion and sedimentation.
The steeper slope is protected from erosion by
vegetation .
Blankets are not necessary in this situation
because of the small slope pitch.
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Clean Water!
The disturbed banks of the ditch have been
protected with mulch and silt fences were
installed for sediment control during grading.
The ditch was stabilized with vegetation prior to
adjacent land disturbance.
Erosion Control BMP Straw mulching on disturbed
banks.
Sediment Control BMP Silt fence installed
adjacent to graded area.
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Check Dams
Such check dams provide channel grade stability
and help to trap sediment, but should be used
only in small upland drainages and gullies, not
in streambeds.
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Fiber rolls can also be used, but need to be
staked well. Another option is to cover fiber
roll and with 4 aggregate.
Spacing of the Check Dams will depend on the
pitch of the grade.
They should be heavy enough to withstand rapid
water flow but not so high or wide as to create
damming or flooding of the road or erosion of the
adjacent slope.
Check Dams are used to slow the rate of water to
help avoid overloading downhill culverts and
drainage ditches.
Some of the materials used for Check Dams include
straw bales, large rock, gravel bags, sand bags,
or reusable products as in the picture below.
They also reduce sediment flow.
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The use of check dams to slow the flow of water
is also a sediment control BMP.
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Large Woody Material

• Large woody material (LWM) is defined as stumps,
  rootwads, and logs having a diameter greater than
  6 inches and length greater than 10 ft

Photo courtesy of Kristen Kittleson
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Why is Large Woody Material important in a creek?

• Ecological Function of LWM

• Stores fine sediment
• Retains spawning gravel
• Forms pools

• Provides cover and nutrients
• Provides habitat for invertebrates

• Recruitment of LWM
• Tree mortality
• Channel migration
• Bank erosion
• Landslides
• Snow avalanches

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Woody Material BMPs

• Consult resource staff and DFG
• Remove only when road or facilities are
  threatened
• Consider modifying before removing
• Limit modification/removal to wood 2 ft above
  stream bed
• Consider upstream and downstream consequences
• Use removed wood for stream bank repairs

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Woody material plugging box culvert
Cut Log
Log Blocking Culvert
No heavy machinery entered the creek for this
project, thus leaving the riparian area
undisturbed. However, relocation of the entire
log within the channel would have provided more
ecological benefit to the stream system.
Removed Sediment
The stored sediment behind the log was not
modified and the upstream and downstream
consequence are unknown.
Instead of removing the entire log, it was chain
sawed into pieces small enough to pass through
the culvert.
Here is an example of a logjam modification
project.
Cut Log
Photos courtesy of the California Department of
Fish and Game
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Streambank Protection

• FishNet Roads Manual BMP Toolbox
• Streambank Protection BMPs
• Biotechnical
• Hardscape