Erosion Control

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Erosion Control
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Erosion Control is the Key to Effective Storm
Water Management for Road Maintenance
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• Each raindrop in a storm event strikes the ground
  at a speed of over 20 miles per hour, dislodging
  far greater than its own weight in soil,
  depending on the type of ground it strikes.

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TYPES OF EROSION
Splash Erosion
From raindrops
From lots of raindrops gaining speed and moving
unchallenged
Sheet Erosion
Caving in under the pressure of splash and sheet
runoff
Rill Gully Erosion
Total surrender. Will be carried away to the
ocean creating a hazard for aquatic life.
Streambank Erosion
Courtesy of EPA
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Definitions
The Best Management Practices for road
maintenance falls into three categories

• Erosion Control Minimizing the movement of
  soil/dirt from its place on a slope.
• Sediment Control Catching sediment that is
  being transported by wind, water, or vehicle
  tires.
• Water Management Controlling the flow of water
  on and off a work site.

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Erosion Control vs. Sediment Control
Erosion Control means
Taking the necessary steps to minimize all forms
of erosion caused by human disturbance of land.
This is achieved by preserving vegetation,
hydroseeding, mulching, erosion control blankets
and other techniques. Erosion is minimized when
BMPs are applied properly.
Sediment Control means
Recovery of particles of soil or pollutants after
they have already been dislodged. This is much
more difficult and costly than prevention, and
MUST be used in concert with erosion control to
be effective.
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Sediment Discharge Prevention Key Elements for
Success

• Manage run-on and run-off. Keep run-off
  velocities low.
• Integrate effective combination of erosion and
  sediment control on all disturbed areas
  particularly during the rainy season.
• Train all staff and contractors on proper use of
  BMPs and installation.
• Inspect and maintain Erosion and Sediment Control
  BMPs.
• Inspect frequently pre- and post storm to assess
  effectiveness of BMPs installed.

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Rates of Erosion
Active surface mines and construction top the
list, causing 2,000 times as much erosion as is
normally present in a forest
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Example of Excessive Sediment Discharge due to
NO Erosion Control Measures
This photo shows a construction site during the
rough grading and underground work. The river of
muddy water, rills and gullies is a result of
poor planning, lack of run-on diversion and not
having the appropriate erosion control BMPs in
place. Preplanning and implementation of Erosion
Control measures would have minimized this muddy
discharge.
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FirstPreserve Vegetation to Extent Feasible.
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Erosion Control Measures

• Mulching Straw is the customary material used
  for mulching for erosion control BMP
• Erosion Control Blankets Woven of a chosen
  material (straw, coconut fiber) and used to slow
  the flow of water across the surface.
• Hydroseeding A planting process which utilizes a
  slurry of seed, tackifier and mulch. It promotes
  quick germination and inhibits soil erosion.
• Soil Stabilizers Materials applied as a spray
  to stabilize bare soil.
• Soil Tracking Roughening a bare soild surface
  to reduce runoff velocity and increase water
  infiltration.

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Erosion Control BMPMulch
Orange fence delineates property and/or work site
or sensitive area boundary
In this example, straw mulch is the primary
erosion control measure.
Silt fence is used for sediment control, not
erosion control.
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Mulching a slope using shredded straw bale for
erosion control the best use of straw bales!
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Proper Erosion Control Using Mulch Results
in Clear Runoff
Straw mulch on this flat area has absorbed the
erosive energy of the rain drops. The storm
water leaving this site is clear.
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Erosion Control BMPErosion Control Blankets

• Consist of degradable natural and/or synthetic
  components.
• Protect the newly seeded soil from erosion for 6
  to 60 months.
• Rely on vegetation alone for long term erosion
  protection.
• Provide erosion control by providing protective
  cover from rainfall impact and surface flows.
• Act as a mulch for seed beds.
• Retain structural integrity and effectiveness
  under severe conditions.

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Erosion Control Blankets
Whether blankets are installed by rolling down a
slope or rolled across a slope is partly a matter
of personal preference and safety which often
depends on the steepness of the slope. The most
important thing is to roll the blanket loosely to
avoid bridging terrain and proper overlapping
and keying in at the top of each roll.

• Properly installed erosion control blankets are
  recommended for more extreme conditions, where
  the slope is greater than 2 to 1

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Because this slope isnt very steep, the
installer also has the option of installing the
blankets perpendicular to the slope.
If youre starting the blanket at the top of the
slope, its best to overlap the next roll.
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EROSION CONTROL BLANKETS
These blankets were installed vertically due to
the steepness of the slope.
Hydro-seeding was applied to the flat area for
long term sediment and erosion control.
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Biodegradable netting
Erosion Control blankets made with biodegradable
netting have the advantage of being
environmentally sensitive to little critters that
might otherwise get tangled up in plastic netting.
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Look, Ma! One hand!
Notice that the blanket is being installed
perpendicular to the slope and starting at the
bottom. Because the slope is not steep this may
be an easier and more efficient way of laying the
blanket. By starting at the bottom the installer
is able to overlap as in shingling a roof.
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Notice that the installer is stapling or crimping
the blankets where they overlap.
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Criteria for Successful Use of Erosion Control
Blankets

• Select the proper blanket for the application.
• Proper key-in in 6 x 6 trench.
• LOOSE installation to maintain direct contact
  with soil.
• Use adequate staples depending on slope
  steepness.

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Proper installation is very important. Notice the
blanket is being undermined and failing because
it was not anchored, or properly keyed in at
the top.
One solution is to anchor the blanket at the top
of the grade by properly installing fiber rolls
on top of it. Simply staking the blanket will not
last for long.
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Example of how to anchor the blankets on the top
of the slope using fiber rolls
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Erosion Control Blankets should be installed
loosely to hug the slope without creating
bridging over uneven terrain. You can see how the
blanket almost wraps around the rocks and
boulders.
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Erosion Control BMPSoil Stabilizers
Hydroseeding
There are a number of different kinds of soil
stabilizers on the market. They are a temporary
BMP solution for erosion, sediment and/or dust
control. Click on the link for more
information http//www.cabmphandbooks.com/Documen
ts/Construction/EC-5.pdf
Close-up
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• Question This guy is
• Spraying fruit flies
• Hydro-mining for gold
• Applying a soil stabilizer

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Three step hydroseeding with mulch
Step One Apply seed and fertilizer Step Two
Apply mulch (2 tons per acre) Step Three Apply
tackifier (glue)
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Bonded Fiber Matrix - BFM

• Stabilizing of completed slope using a bonded
  fiber matrix (BFM) hydro seeding process with a
  liquid tackifier. In the foreground the completed
  slope has been tracked correctly to decrease the
  velocity of runoff and allow the seeds to take
  hold properly.

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These are examples of Bonded Fiber Matrix
application as an Erosion Control BMP on the road
side drainage system.
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Soil tracking creates pockets for rain and
seeds to collect.Tracking across slopes
increases erosion, while tracking up and down the
slope creates mini-terraces, or serrations
Erosion Control BMPSurface Roughening/ Soil
Tracking
c
Courtesy San Francisco Estuary Project and
SFBRWQCB
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Stepped or terraced slopeProper terracing and
contouring of graded slopes slows the velocity of
running water, and therefore reduces erosion.
c
Courtesy San Francisco Estuary Project and
SFBRWQCB
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Proper Tracking of Slope

• Do not use this BMP
• On slopes with a rock surface
• Unless simultaneous revegetation/ seeding is
  planned

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Examples of Erosion Control BMPs Mulch, Bonded
Fiber Matrix, and Erosion Control Blankets
Bonded Fiber Matrix
Erosion Control Blankets for steep slopes
Mulch and Tackifier
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These slopes were blanketed, but applying mulch
or Bonded Fiber Matrix could also work.
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Erosion Control for Cutslope Failure
Cutslope failure is a common occurrence during
winter storms.
Debris slides and surface erosion can contribute
sediment to the stream system via the inboard
ditch.
Photos by Tyler Ledwith
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Cutslope Stabilization Options
(Below left) An erosion control blanket can
provide immediate temporary mitigation. It should
also be accompanied by sediment control BMPs
(coir log, silt fence, straw bale) to minimize
any sediment that might get carried by the
inboard ditch that empties into the stream
network.
There are several options available in treating
cutslope failures, from engineered hardscaping
(i.e. revetment walls) to simple bioengineering
techniques.
Hydroseeding the slope (below right) is another
remedy for longer term mitigation. It is best to
seed in conjunction with laying erosion control
blankets, and should be accompanied by the
sediment management BMPs.
A few Erosion Control BMPs that can easily be
installed by maintenance crews are erosion
control blankets, seeding, mulching, and/or rock
placement at the base of a slide.
Hydroseed
Coir/geotextile Fabric
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Cutslope Stabilization Options
A large rock base will probably be the quickest
temporary fix for a slide like this.
Sediment Control BMPs (i.e., coir log, straw
bale, silt fence) should also be installed to
trap any sediment carried by the inboard ditch
that empties into the stream network.
Rock
Sediment Control BMPS
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The Final Word on erosion control for any road
construction or maintenance project...
Straw Mulch is for Erosion Control!
Straw bales are for horses!
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Erosion ControlRefer to the FishNet Roads Manual
BMP Toolbox

• Erosion Control BMPs
• Blankets/Geotextiles
• Coir Fabric Netting
• Coir logs/Straw rolls
• Broadcast seeding
• Hydro-seeding
• Mulching
• Planting

• Surface Roughening and Soil Tracking
• Stepped or Terraced Slope
• Plastic Covering
• Rock Breast Wall
• Vegetated Geoberm Toe Wall