Streambank Protection Methods Bio-Engineering Techniques

Streambank Protection Methods
Bio-Engineering Techniques
Instructor:
David T. Williams, Ph.D., P.E.
David T. Williams and Associates, Engineers
david@dtwassoc.com

Bioengineering
**? What Are You Trying To Do? **
Did I Mention, Function-based Design?
PROBLEMS: For rills & gullies from overland flow, strong and
dense rooted ground covers or grasses might function well.
Use pioneer species that will stabilize the bank and evolve into
a climax forest?
Plant specific plants for use by specific fauna?
Do you need an understory, mid-story and overstory? Or not?

Do you need no mid-story for woodpecker flyways?
Will the overstory shade out the understory?
Vegetative roughness or living dikes to reduce flow
velocities & catch sediment?
Do you need shade and canopy over the stream?
Microhabitats?
Insect production for the stream?
Tall vegetation and canopy to keep cool moist air over the
stream?
Flood concerns? Use herbaceous plants!?!?

Bioengineering Planting Considerations
First look up, then look down, (up to analyze for amount of light
and overhead power lines, down for suitable soil & pipeline right-ofways),
then look around for exotic plant competition, and where (or
if) the plants of choice are growing naturally.
Plants on opposite banks might grow in different elevation bands.
If plants are not found naturally, why?
Plant materials obtained through commercial growers, NRCS plant
material centers, grown in-house, or harvested from the wild.
Harden-off rooted-stock plants (place outside greenhouse) before
planting.

Bioengineering Planting Considerations
Harvested cuttings should be kept moist/out of direct sunlight.
Some cuttings benefit from soaking (up to 31 days for Black
Willow). Water that plants are soaked in should be fresh.
Very important to have good soil-to-stem contact, this must be
carefully specified in contracts
Plantings need to be closely monitored for insect infestation and
mortality, some replanting can be expected during the second
growing season.
Is irrigation needed? Weed control? Browsing control?

Advantages of Vegetation
Filters runoff
Safer than riprap - less chance of contact injury
Aesthetically pleasing
Improved wildlife habitat

Advantages of Vegetation
Improved fish habitat (cover food, shade)
Enhanced passive recreational activities
Source of carbon matter to the stream system
Canopy helps to lower water temperatures and reduce
soil erosion
No graffiti (actually not always)

Environmental Functions of
Vegetative Bank Protection Structures
Provide cover.
Stabilize or lower water and air temperatures .
Trap cool moist air moving (traveling) immediately above water.
Maintain dissolved oxygen levels.
Supply carbon material to the stream (leaf litter, debris, SWD &
LWD).
Provide habitat, food and shelter for insects and other critters,
nesting areas, migration corridors, cover from predators, & other
good riparian buffer zone features.

Environmental Functions of
Vegetative Bank Protection Structures
Provide nutrient uptake and long-term storage of nutrients &
contaminants
Trap sediment, reducing sediment load to stream
Reduce water content of bank, drier banks are usually more
stable
NOTE: Stream stabilization might not necessarily be good for
terrestrial habitat diversity. With time, all riparian areas could
become climax communities & vegetative diversity and
complexity would be reduced.

Uncontrolled Variables
That Affect Vegetation
Soil types - highly erodible, acidic, anaerobic, etc.
Soil heterogeneity
Climate
Rainfall distribution - space and time
Temperature
Season

Elevation
Uncontrolled Variables
That Affect Vegetation
Competition from other plants and noxious weeds
Vegetative succession
Maintenance
Stream variables - flood events, stages, durations, velocities
IMPORTANT NOTE: Engineers and others need to
understand that growing vegetation is complex and not
every plant will live and grow.

Urban Soils
In many cases reclamation, not revegetation (no vegetation
to begin with, only bare soils).
Soils are typically disturbed.
Relatively sterile - little or no organic material.
Composed of subsoils, not top soils.
pH can be high, low, or neutral.
Can be located in very inhospitable areas (chemical
pollution, thermal pollution, etc.)

Why Some Folks Are
Reluctant to Use Vegetation
Both plant biological needs and hydraulic design parameters for
plants must be met.
Knowledge of hydraulic design parameters or limits for plants is
currently incomplete.
Known hydraulic parameters change with experience/failures
Vegetation is not always immediately effective.
Everything listed on the "Uncontrolled Variables that Affect
Vegetation" slide.
Participating agencies, designers, contractors, and/or inspectors
might not have much, or any, experience with vegetative fixes.

How Vegetative Treatments
Stabilize Banks
Foliage slows floodwaters on and near the eroding bank.
Root network helps to bind soil together.
Trunks and stems can trap debris and upslope failed material.
Vegetation removes soil moisture through transpiration.
Larger branches/trunks planted deep can sometimes
mechanically stabilize soil and could pin shallow failure faults.
Can induce sedimentation.
Most importantly, the resulting stable bank allows for the
establishment of volunteer plant growth and subsequent
vegetative succession.

Bioengineering Methods
Consider integrating when stone is placed or retrofitting existing
projects: Soil "choked" & seeded riprap with rooted stock plants in
interstecies
Live Staking and Joint Planting
Brush Layering, Brush Layering with Rock Toe
Bent Willow Pole Method
Live Wattles (branches every which-a-way), Live Fascines (branches
bundled in one direction only), and Reinforced Wattles and Fascines
Turf Reinforcement Mats (TRM’s) and Erosion Control Blankets (ECB’s)

Bioengineering Methods
Coir Fiber Rolls and Mats (including pre-seeded and pre-grown)
Brush Mattress
Tree Revetments (Cedar Tree Revetments)
Live Siltation combined with LPSTP
Dormant Willow Post Method
Willow Poles and Willow Curtains
Debris Dikes and Living Dikes (sediment catchers and velocity
reducers)

Soil-Choked
RIPRAP
From John McCullah’s
www.E-SenSS.com

Live Staking
(Also Called "Sprigging", Pencils" or "Whips")
Description: Manual vertical insertion of small sharpened
willow cuttings (branches 18 to 30 inches in length, 1/2 to 3/4
inch diameter) in the lower sections of stream banks. Can either
be pushed in by hand or a tile probe can be used to poke a hole
in the bank with the branch inserted in the hole. Can be placed
in and around bioengineering projects or "hard" structures.
No mechanized support needed.
Inexpensive, simple, versatile, and quick!
No material cost items.
Two man crew can install up to 500 sprigs a day.
Can be planted from on-bank or canoe.

Joint Planting is the
same as Live Staking
except it is driven
through or integrated
into the riprap or other
armor (through the
joints or interstecies of
the armor material)

Weighted toe, designed to
self-adjust into scour hole
Joint Plantings
VEGETATED RIPRAP
w/ BRUSHLAYERING,
POLE PLANTING,
& JOINT PLANTING

Individual poles pulled up & growing
This method
invented by
Chris Hoag

The Bent Willow Pole Method
A John McCullah invention
This technique is used to integrate large willow poles behind
(landward of) a riprap protection scheme
Poles can be laid on the bank (butt ends in water or vadose
zone), covered with riprap, the upper ends bent to a vertical
position, then rocks wedged behind pole to keep pole oriented
vertically
Allows willows to grow in some areas (UP BANK) where naturally
might be too dry for vigorous willow growth

This method
invented by John
McCullah!

Riprap can also be choked with
soil for better rooting
Self-Adjusting, Self-
Filtering Stone can
also be used in this
application

LIVE FASCINES
Always placed on a
slope, branches in
fascine bundle are all
oriented in the same
direction, tips angled
upslope, butt ends
positioned downslope

Note sediment
landward of
coir roll just
days after
construction,
note pre-grown
black willow
trees in roll, all
drowned due
to DS beaver
dam backwater

Bioengineering Top 11 Cheat Sheet
1. Dig a hole, plant a pole!!! McCullah’s mantra for the bioengineer.
2. For unrooted stock, plant 80% in soil, 20% out.
3. Good stem to soil contact is critical, tamp and WATER
MATERIAL IN!!
4. Use a variety of techniques and plant materials and material sizes
5. No starter rills, mulch if needed
6. Plant the keys with both large and small material.

Bioengineering Top 11 Cheat Sheet
7. No “Droopers” - all plantings should be angled at 10-20 degrees
above horizontal or more.
8. Use dense rows of plants to trap sediment and/or act as "living
dikes“
9. What type and where was historical vegetation located in the
system?
10. Consider herbaceous plants (sedges, reeds, emergent aquatics,
etc.)
11. If needed, and if possible, use BIODEGRADABLE Turf
Reinforcement Mats and Erosion Control Blankets.

The Dormant
Willow Post
Method, and
Willow Poles
(Various Styles)

Advantages of Planting Willows
Early or Late in the Dormant Season
EARLY
Willows put energy into growing roots (at least until ground
temperature reaches approximately 45 degrees or colder)
Ground not frozen.
Consider interaction of plants with ice (shear and lifting)
LATE
Less chance of ice damage.
Less chance of beaver damage.
NOTE: Carefully weigh advantages and disadvantages for your
particular situation and area of the country.

The Willow Curtain Method
Description: Horizontal placement of anchored willow tree trunks in a
shallow trench positioned near water's edge. Can be placed on benched
areas at heights just above the low-flow water surface elevation or on the
point bar (in low sections or near the edge) to increase flow resistance and
reduce the impact of concentrated flow on the eroding outer bank.
Can be accomplished with no mechanized support.
Very inexpensive, simple to understand and execute, and quick!
Anchor with dead stout stakes or live stakes.
Five 20 ft. long willows will cover 100 ft of stream bank.
A two man crew installed 300 lineal ft. of curtains in 3 hours.
Need to be installed in areas with sufficient moisture.
This WES developed technique is currently considered experimental.
From Dave Derrick, USACE, ERDC

Inexpensive, simple, and quick!
Willow Pole Method
Description: Anchored willow tree trunk placed with the butt end buried
below the water surface at the toe of the eroding bank, trunk positioned upbank
in a shallow trench. Water is supplied at base, roots grow from trunk
which is in contact with the soil all the way up the bank, with branches
sprouting along the entire length of the "up" side of the trunk.
On eroding banks should be used in combination with redirective methods or
toe protection.
Can be accomplished with no mechanized support, excellent for areas
where equipment access is limited or prohibited.
Expensive auguring equipment is not needed.
Anchor with dead stout stakes or live stakes.
This WES developed technique is currently considered experimental.
From Dave Derrick

Be Aware of Vegetative
Maintenance Regulations
COE ETL 1110-2-571: Guidelines for Landscape
Planting and Vegetation Management at Levees,
Floodwalls, Embankment Dams, and Appurtenant
Structures (2009)
State and Local Regulations