Bank Stabilization & Improvement

8/2/2019 Bank Stabilization & Improvement

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Bank Stabilization and Improvement of Huron Creek in the Kestner Waterfront Park Houghton, Michigan

Park Description The Kestner Waterfront Park is located within the city limits of Houghton, Michigan along Portage Lake. Due to its scenic location and ample facilities, the park is one of the most popular in the city. Facilities include a swimming beach, launch site for kayaks and sailboats, an extensive playground area, picnic tables, grills and a lakeside walking path. An RV park is located immediately to the west, and boat docking and launching facilities are located immediately to the east of the park proper. The park also has a pavilion and band shell, making it a prime location for many outdoor events and gatherings. A photo of the north side of the park is providedas Figure 1 below.

Figure 1 Kestner Waterfront Park Figure 2 Huron Creek in Park, September 2007

Purpose of the Project The primary goal of this project is to improve the channel of Huron Creek in Kestner Waterfront Park to provide slope stability and more attractive, naturalized streambanks. Huron Creek travels through the Kestner waterfront park for approximately 350 feet before flowing into the Portage waterway beneath a concrete walkway. Historically there have been repeated problems with the banks of Huron Creek washing out from erosion during storms. A severe storm in September 2007 caused several bank areas to completely fail (Figure 2) resulting in steep, undercut and unprotected slopes. Various methods have been used to attempt to stabilize the banks over the years including riprap, herbaceous plantings and erosion matting with lawn grass. Each method has eventually given way to bank erosion.

In an attempt to repair the banks and ideally stabilize them permanently, the City of Houghton is proposing to implement biotechnical stabilization along the bank areas in the park as shown in the attached Figure 3. The stabilization will consist of three components: (a) installation of rock filled gabions at the toe of the bank slopes to protect against erosion during high flow events; (b) re grading the bank slopes to grades of between 3H:1V and 2H:1V; and (c) planting the slopes and gabions with native trees, shrubs and grasses.

Essential Elements of Project The following items describe the biotechnical stabilization method proposed by the City of Houghton:

1. Excavate slopes back to a shallower angle; 3H:1V where possible, otherwise 2H:1V given a buffer strip width of 12 to 18 feet.

2. Install two levels of stone filled gabions at the toe of the slope. The bottom gabion is to be sunk into the creek bed to provide

protection against undercutting. Both the top and bottom gabions are to be installed at an angle to provide against the potential for sliding. A typical cross section of an improved slope is provided as Figure 4.

3. Plant native shrubs into bank on top of upper gabion to provide additional toe and bank stabilization. This measure, along with the lower gabion being sunk into the creek bed will help cover the gabions to add a more natural look to the creek while sufficiently stabilizing it. Figure 5 shows typical native shrub placement on top of the gabions.

4. Plant a mixture of native grasses, shrubs and trees within a 12 to 18foot buffer strip along biotechnical stabilization areas. This will contribute to bank stabilization, help cover and prevent access to the gabions, and help create a more natural creek corridor. Planting locations and details are provided on Figures 6 and 7. Native plant species are included in drawing notes and an attachment.


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The City of Houghton acknowledges that the Michigan Coastal Management Program generally does not support the use of hard shore protection such as gabions. However, after several tries at stabilization, and discussions with local experts such as Natural Resource Conservation Service (NRCS) representatives, it is our conclusion that hard stabilization at the toe of the banks is necessaryfor longterm success. Velocities of Huron Creek in the Kestner Waterfront Park can exceed those allowed as maximum for soft measures such as coir logs or lone vegetative stabilization. These high velocities can be attributed to steep topographies (surface slopes exceed 10%15% in some locations) and a significant amount of urban development upstream.

Relationship to Larger Projects This proposed project is also being completed in support of the Huron Creek Watershed Management Plan (MDEQ grant trac king

#2006 0162) which is being funded by the Michigan Department of Environmental Quality. The Michigan Technological University (MTU) Center for Water and Society (CWS) is responsible for developing the watershed management plan. A watershed advisory committee (WAC) was formed in 2006 as part of the watershed management planning efforts. Since the Kestner Waterfront Park provides one of the few places in the watershed where visitors can interact with the creek, it is a goal of the Huron Creek WAC that this location be utilized to spread awareness of the creek and watershed management. The Huron Creek WAC has recommended that improving the banks of the creek would provide a healthy, visually appealing creek would and encourage support to protect and restore the remainder of the Creek. An interpretive sign describing the Huron Creek watershed and watershed health was installed in the park adjacent to the creek in 2007.

The MTU CWS has provided designs, calculations, cost estimates and drawings for submittal with this proposal as well as for inclusion in the watershed management plan.

Improvements to Huron Creek in the Kestner Waterfront Park have been suggested in the City of Houghtons Recreation Plan

2008 2013 (see http://www.cityofhoughton.com/news/45.pdf ). Relationship to Existing Facilities In the Kestner Waterfront Park, Huron Creek is located centrally between a popular swimming area and another small beach and boat launching area. After some storm events, eroded sediment and debris can be seen along the banks and discharging from the mouth of the creek into Portage Lake towards these areas. This can create visually displeasing conditions at these locations, as well as negatively affect the water quality.

Project Budget

Gabion materials and installation $48,000

Bank grading $15,000

Grass, shrubs, trees, fertilizer and installation $12,500

Erosion mat, stakes and installation $6,500

TOTAL $82,000

Funding Source Local match for this project includes funds appropriated by the City of Houghton for the city recreation plan and inkind labor.


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A: 120 ft

outlet

NStabilize

B: 130 ft

Stabilize Plall

C: 30 ft - Stabilize

D: 50 ft - Open

sca

arkin

E: 80 ft - Open

G: 50 ft - Stabilize

lot

sidewalks

F: 50 ft - Stabilize

I: 55 ft - StabilizeH: 50 ft -Stabilize

road


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Stak

set second

gure :

Typical BankCross-Section plant slopes with nativegrass, shrubs and trees

annew

> 2:1

gabionback ~ 9 in

all dimensions areapproximate

finisgabibed

creek

~ 5 ft

Two (2) ~3 ft x 3 ft galvanized gabions6 . Fill with 4 to 8

excavate~

below bed

filter cloth placed underand behind gabions


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Figure 5:

Examples of Shrub Placement in or on Gabions

Shrubs to be planted 2 perstack of 6-foot long gabions

creek

s ope(see detail)

bed

Shrub Planting Detail (view from creek or bank)

2 2 2 Ball-stock shrubs (w/ root ball included)

http://www.epa.gov

Gabions


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Figure 6: Vegetation Detailsrefer to Figures 3 and 8 for location

T ical Ve etative Buffer Stabilize Typical Vegetativ

All dimensions are approximate. Shrub and tree placement shown is not exact - for figurative purShrubs can be live stakes or balled stock (root ball included). See notes for more planti

12-18 ft

OpenErosion matover entirebuffer

Plant nativegrasses and

shrub density:~ 1 shrub per3-5 sq. ft

forbs only

Native grasses and

forbs intermixedamong shrubs andtrees (hatching not

trees

shrubs

grassess own

scale: approx. 25 ft /in

gabions & forbs


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A

outlet

BPlImseedetD,

scaarkin

DE

lot

sidewalksF

G

H

road


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NOTES:1. Bank planting & grading areas should be kept to a maximum12-foot width near sidewalk

(Areas E and F).

2. Bank slopes shall be graded to 3H:1V where possible, otherwise 2H:1V.3. If sediments from the creek bed are mechanically removed as part of regular park

,keep them in place.

4. GABIONS:Nearest supplier of Macaferri gabions is CSI Geoturf Contact: David Ringle.Phone: 231 943-4002657 W. Blue Star Drive, Traverse City, Michigan 49684

Technical support and CAD drawings (sometimes for free for public projects):Macaferri GabionsKen Hughes/Tersea Lynch 2351 Versailles Rd., Ste. 302 Lexington, KY 40504

- a : o ce macca err -usa.com e ep one: 859.255.1343

See attached Macaferri specification sheet for gabions sizing and installation informatio

5. See attached U.S. Army Corps of Engineers document SR-22, Gabions for Streambank.

6. Cost provided for gabions is for galvanized gabions only (not PVC-coated). Cost includshipping and enough wire for gabion assembly. Can also purchase hog rings for connethat can be easier to use/install- additional cost for 90 gabions ~ $700.00.

7. GRASSES:a) A suggested mesic (tolerant to dry and wet conditions) seed mix is attached. Th

seed mix has been provided by Borealis Seed Co., Marquette, MI. (906) 226-850b) Suggested application rate = 1 lb/3,000 sq.ft. Plant throughout vegetated area


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NOTES (continued):8. SHRUBS:

red-osier dogwood (Cornus stolonifera) ninebark (Physocarpus opulifolius) upland willow (Salix humilis) pussy willow (Salix discolor)

b *Shrubs lanted on to of abions should be balled stock for best establishment. planted on bank can be balled stock or live stakes. Live stakes are less expensive, bstock establishes more quickly. Also live stakes look, initially less visually appeali

9. TREES:a) Suggested species of trees:

red maple (Acer rubrum) quaking aspen (Populus tremuloides)

white or paper birch (Betula papyrifera)

10. EROSION BLANKET & STAKES: .

b) 6 wire stakes are recommended for fastening to bank. See manufacturer instructioproper installation.

c) Erosion blanket to be installed and secured after seeding and fertilization.

11. Su liers of Trees Shrubs and Erosion Mat:a) Lake Superior Tree Farm, Chassell,MI, 906-523-6200 (Contact: David Crouch)b) Great Lakes Nursery, Watervliet, MI, 269-468-3323, www.greatlakesnurserycc) Cold Stream Nursery, Free Soil, MI, 231-464-5809, www.coldstreamfarm.net/d) Engels Nursery, Fennville, MI, 296-543-4123, www.engelsnursery.com/ e) *Follow vegetation supplier instructions for planting, fertilization and care.

10. Fertilizer should be applied to bank area when planting vegetation. 3/10/10 fertilizer isrecommended. Slow-release fertilizers are not recommended. Follow manufacturer applicinstructions closely.


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ERDC TN-EMRRP SR-22 1

Low Moderate High

Complexity

Low Moderate High

Environmental Value

Low Moderate High

Cost

Gabions for StreambankErosion Controlby Gary E. Freeman 1 and J. Craig Fischenich 2 May 2000

1 River Research and Design, Inc., 1092 N. 75 E., Orem, UT 840572 USAE Waterways Experiment Station, 3909 Halls Ferry Rd., Vicksburg, MS 39180

OVERVIEWGabions are cylinders that are filled with earthor stones, which are used in building structuressuch as dams or dikes. Gabions have been

used for several millennia in Egypt and China.Prior to 1879, gabions were constructed withplant materials, which severely limited theiruseful life. In about 1879 a firm in Italy isthought to have first used wire mesh in theconstruction of gabion baskets. This ispossibly the first use of the modern wire meshbaskets as used today. Gabions are now usedthroughout the world for bed protection, bankstabilization, retaining walls, and numerousother purposes.

Gabions come in three basic forms, the gabionbasket, gabion mattress, and sack gabion. Allthree types consist of wire mesh baskets filledwith cobble or small boulder material. The fillnormally consists of rock material but othermaterials such as bricks have been used to fillthe baskets. The baskets are used to maintainstability and to protect streambanks and beds.

The difference between a gabion basket and agabion mattress is the thickness and the aerialextent of the basket. A sack gabion is, as the

name implies, a mesh sack that is filled withrock material. The benefit of gabions is thatthey can be filled with rocks that wouldindividually be too small to withstand theerosive forces of the stream. The gabionmattress is shallower (0.5 to 1.5 ft) than thebasket and is designed to protect the bed orbanks of a stream against erosion.

Gabion baskets are normally much thicker(about 1.5 to 3 ft) and cover a much smallerarea. They are used to protect banks where

mattresses are not adequate or are used tostabilize slopes (Figure 1), construct dropstructures, pipe outlet structures, or nearly anyother application where soil must be protectedfrom the erosive forces of water. References togabions in this article refer generally to bothmattresses and baskets. Sack gabions arerarely

Figure 1. Gabion baskets installed forslope stabilization along a stream

used in the United States and are not within thescope of this technical note.Gabion baskets can be made from eitherwelded or woven wire mesh. The wire isnormally galvanized to reduce corrosion butmay be coated with plastic or other material toprevent corrosion and/or damage to the wiremesh containing the rock fill. New materials


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2 ERDC TN-EMRRP SR-22

such as Tensar, a heavy-duty polymer plasticmaterial, have been used in some applicationsin place of the wire mesh. If the wire basketsbreak, either through corrosion, vandalism, ordamage from debris or bed load, the rock fill inthe basket can be lost and the protective valueof the method endangered.

Gabions are often used where available rocksize is too small to withstand the erosive andtractive forces present at a project site. Theavailable stone size may be too small due tothe cost of transporting larger stone fromremote sites, or the desire to have a projectwith a smoother appearance than obtainedfrom riprap or other methods. Gabions alsorequire about one third the thickness ofmaterial when compared to riprap designs.Riprap is often preferred, however, due to thelow labor requirements for its placement.

The science behind gabions is fairly wellestablished, with numerous manufacturersproviding design methodology and guidance fortheir gabion products. Dr. Stephen T. Maynordof the U.S. Army Engineer Research andDevelopment Center in Vicksburg, Mississippi,has also conducted research to develop designguidance for the installation of gabions. Twogeneral methods are typically used todetermine the stability of gabion baskets instream channels, the critical shear stresscalculation and the critical velocity calculation.A software package known as CHANLPRO hasbeen developed by Dr. Maynord (Maynord etal. 1998).

Manufacturers have generated extensivedebate regarding the use and durability ofwelded wire baskets versus woven wirebaskets in project design and construction.Project results seem to indicate thatperformance is satisfactory for both types of

mesh.

The rocks contained within the gabions providesubstrates for a wide variety of aquaticorganisms. Organisms that have adapted toliving on and within the rocks have an excellenthome, but vegetation may be difficult toestablish unless the voids in the rockscontained within the baskets are filled with soil.

If large woody vegetation is allowed to grow inthe gabions, there is a risk that the baskets willbreak when the large woody vegetation isuprooted or as the root and trunk systemsgrow. Thus, it is normally not acceptable toallow large woody vegetation to grow in thebaskets. The possibility of damage must beweighed against the desirability of vegetationon the area protected by gabions and thestability of the large woody vegetation.

If large woody vegetation is kept out of thebaskets, grasses and other desirablevegetation types may be established andprovide a more aesthetic and ecologicallydesirable project than gabions alone.

PLANNING

The first step in the planning process is toascertain whether gabions are the appropriatetool to meet project objectives and constraintsrelated to stability and habitat. Team membersconducting this assessment should includehydraulic engineers, biologists, geologists,landscape architects, and others that have anunderstanding of stream restoration, fluvialgeomorphology, and vegetation and habitatrequirements.Numerous questions must be addressed by theteam including, but not limited to, the following

interrelated items:1) Are gabions the appropriate tools given

the magnitude of the erosion problem?2) Are stream velocities and shear stresses

permissible?3) Is there danger to the wire mesh from

floating debris, sharp bed load, or fromvandalism?

4) Will site conditions during constructionpermit installation?

5) Have consequences of failure been

considered and what are they, e.g., whathappens if one or several basketsbecomes dislodged and move downstreamor break open?

6) Can and will the sponsor repair thebaskets in a timely manner whennecessary?

7) Are there areas that must be protected toprevent erosion damage from the upperbank areas behind the gabions?


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8) Are the project costs acceptable?

Costs for gabion projects are among thehighest for streambank erosion and bankstabilization techniques. Costs for the basketsvary by size and depth but are on the order of$1.50 to $3.20/ft 2 (all figures in 1999 dollars) for3-ft-deep baskets, $1.25 to $2.00/ft 2 for18-in.-deep baskets, and $1.10 to $1.75/ft 2 for12-in.-deep baskets. Closure items for thebaskets are normally included and prices alsovary with the gauge of the wire, with heavierwire being more expensive. Baskets can beordered in custom sizes for a higher price.Keys or tiebacks, if required, stone, backfill,and vegetation plugs, if any, add to materialcosts but vary with design and availability.

Total project cost is estimated at about $150.00to $450.00/yd 3 of protection. This includes thebaskets, assembly and filling the baskets,stone fill (may vary depending on location andavailability), and basket closure.

Basket installation does not always requireheavy equipment but the filling and closure ofthe baskets can be very labor-intensive and agood crew should be planned to completeinstallation in a timely manner.

SITE CONSIDERATIONSGabions are suited to a variety of siteconditions. They can be used in perennial orephemeral streams, and installation can occurin dry or wet conditions with the properequipment. The main concern is the deliveryand handling of the baskets and rock fill. If wetconditions exist for long periods of time in thearea surrounding the site, the delivery of rockmaterials may be impossible or extremelyproblematic.

The most important consideration for theinstallation of gabions is the stability of thestream. If the stream is undergoing rapidchanges in base elevation (down- cutting ordeposition) or extreme lateral movement, plansshould be made to correct the larger problemsthat are contributing to the local problem. If thelarger problems are not addressed, localprotection measures may be overwhelmed orflanked.

Foundation conditions are also important in siteselection because the gabions must have afirm foundation. If the substrate is noncohesivematerial, such as sand or silt, the material maybe removed through the gabions and causesettlement or flanking to occur. Installation of afilter material or filter fabric should beconsidered in every project. Filter materialshould only be omitted if it is clearly notneeded. Some projects may require a filterfabric as well as a gravel filter material toprevent erosion of the underlying bank and bedmaterial. An additional and extremely importantconsideration is the calculation of the amountof erosion to be expected in a project. Thisshould be calculated to ensure that thefoundation for the gabions is not undercut dueto scour.

DESIGNPrimary design considerations for gabions andmattresses are: 1) foundation stability; 2)sustained velocity and shear-stress thresholdsthat the gabions must withstand; and 3) toe andflank protection. The base layer of gabionsshould be placed below the expected maximumscour depth. Alternatively, the toe can beprotected with mattresses that will fall into anyscoured areas without compromising thestability of the bank or bed protection portion of

the project. If bank protection does not extendabove the expected water surface elevation forthe design flood, measures such as tiebacks toprotect against flanking should be installed.

The use of a filter fabric behind or under thegabion baskets to prevent the movement of soilmaterial through the gabion baskets is anextremely important part of the design process.This migration of soil through the baskets cancause undermining of the supporting soilstructure and failure of the gabion baskets and

mattresses.Primary Design ConsiderationsThe major consideration in the design of gabionstructures is the expected velocity at the gabionface. The gabion must be designed towithstand the force of the water in the stream.


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Since gabion mattresses are much shallowerand more subject to movement than gabionbaskets, care should be taken to design themattresses such that they can withstand theforces applied to them by the water. However,mattresses have been used in applicationwhere very high velocities are present andhave performed well. But, projects usinggabion mattresses should be carefullydesigned.

The median stone size for a gabion mattresscan be determined from the following equation:

5.2

1

5.0

= gdK V

d C C Sd ws

wvs f m

(1)

The variables in the above equation aredefined as:

C s = stability coefficient (use 0.1)C v = velocity distribution coefficient

= 1.283-0.2 log ( R/W ) (minimumof 1.0) and equals 1.25 at endof dikes and concrete channels

d m = average rock diameter in gabionsd = local flow depth at V g = acceleration due to gravityK 1 = side slope correction factor

(Table 1)R = centerline bend radius of main

channel flowS f = safety factor (1.1 minimum)V = depth-averaged velocityW = water surface width of main

channel s = unit weight of stone w = unit weight of water

Table 1. K1 versus Side Slope Angle

Side Slope K11V : 1H 0.461V : 1.5H 0.711V : 2H 0.881V : 3H 0.98


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Table 2. Stone Sizes and Allowable Velocities for Gabions (courtesy of and adapted fromMaccaferri Gabions)

Type Thickness (ft) Filling StoneRange

D50 Critical*Velocity

Limit**Velocity

Mattress 0.50.50.750.75

11

3 - 4"3 - 6"3 - 4"3 - 6"3 - 5"4 - 6"

3.4"4.3"3.4"4.7"

4"5"

11.513.814.814.813.616.4

13.814.816201821

Basket 1.51.5

4 - 8"5 - 10"

6"7.5"

1921

24.926.2

When the data in Table 2 are compared toEquation 1, if V = 11.5, C s = 0.1, C v = 1.0, K 1 =

0.71, w = 150 and S f = 1.1, the local flow depthmust be on the order of 25 ft in order to arriveat the stone diameter of 3.4 in. shown in Table2. Designers should use Equation 1 to take thedepth of flow into account. Table 2 does,however, give some general guidelines for fillsizes and is a quick reference for maximumallowable velocities.

Maccaferri also gives guidance on the stabilityof gabions in terms of shear stress limits. Thefollowing equation gives the shear for the bed

of the channel:

Sd wb = (2)

with the bank shear m taken as75 percent of the bed shear, i.e. m = 0.75 b .(S is the bed or water surface slope through thereach.) These values are then compared to thecritical stress for the bed calculated by thefollowing equation:

( ) mwsc d = 10.0 (3)

with critical shear stress for the banks given as:

4304.0sin

12

= cs (4)

where = the angle of the bank rotated up from

horizontal.

A design is acceptable if b < c and m < s . ifeither b > c or m > s , then a check must bemade to see if they are less than 120 percentof b and s . If the values are less than 120percent of b and s , the gabions will not besubject to more than what Maccaferri definesas acceptable deformation. However, it isrecommended that stone size be increased tolimit deformation if possible.

Research has indicated that stone in thegabion mattress should be sized such that thelargest stone diameter is not more than abouttwo times the diameter of the smallest stonediameter and the mattress should be at leasttwice the depth of the largest stone size. Thesize range should, however, vary by about afactor of two to ensure proper packing of thestone material into the gabions. Since themattresses normally come in discrete sizes, i.e.0.5, 1.0, and 1.5 ft in depth, normal practice isto size the stone and then select the basket

depth that is deep enough to be at least twotimes the largest stone diameter. The smalleststone should also be sized such that it cannotpass through the wire mesh.

Stability of Underlying Bed and BankMaterials. Another critical consideration is thestability of the gabion foundation. This includesboth geotechnical stability and the resistance ofthe soil under the gabions to the erosive forces


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of the water moving through the gabions. Ifthere is any question regarding the stability ofthe foundation, i.e. possibility of rotationalfailures, slip failures, etc., a qualifiedgeotechnical engineer should be consultedprior to and during the design of thebank/channel protection. Severalmanufacturers give guidance on how to checkfor geotechnical failure (see MaccaferriGabions brochure as an example).

Stacked gabion baskets used for bank stabilityshould be tilted towards the soil they areprotecting by a minimum of about 6 deg fromvertical. Gabions are stacked using twomethods. These are shown in Figure 3. Whilethe gabions can be stacked with no tilt, it isrecommended that some tilt into the soil beingprotected be provided.

Figure 3. Front step and rear step gabionlayout (courtesy of Maccaferri Gabions)

One of the critical factors in determining

stability is the velocity of the water that passesthrough the gabions and reaches the soilbehind the gabion. The water velocity underthe filter fabric, i.e. water that moves throughthe gabions and filter fabric, is estimated to beone-fourth to one-half of the velocity at themattress/filter interface. (Simons, Chen, andSwenson 1984) The velocity at themattress/filter interface ( V b ) is estimated to be

2 / 13 / 2

2

486.1S

d

n

V m

f

b

= (5)

where n f = 0.02 for filter fabric, 0.022 for gravelfilter material and S is the water surface slope(or bed slope) through the reach. If theunderlying soil material is not stable, additionalfilter material must be installed under thegabions to ensure soil stability. Maccaferri alsoprovides guidance on the stability of soil underthe gabions in terms of velocity criteria.

The limit for velocity on the soil is different foreach type of soil. The limit for cohesive soils isobtained from a chart, while maximumallowable velocities for other soil types areobtained by calculating V e , the maximumvelocity allowable at the soil interface, andcomparing it to V f , the residual velocity on thebed, i.e. under the gabion mattress and underthe filter fabric.

V e for loose soils is equal to 16.1 d 1/2 while V f iscalculated by:

2 / 13 / 2

2486.1

am

f f SV

d n

V

= (6)

where V a is the average channel velocity andd m is the average rock diameter.

If V f is larger than two to four times V e , a gravelfilter is required to further reduce the watervelocity at the soil interface under the gabionsuntil V f is in an acceptable range. To check forthe acceptability of the filter use the averagegravel size for d m in Equation 6. If the velocityV f is still too high, the gravel size should bereduced to obtain an acceptable value for V f .

Other Design ConsiderationsIt may be possible to combine gabions withless harsh methods of bank protection on theupper bank and still achieve the desired resultof a stable channel. Provisions for large woodyvegetation and a more aesthetically pleasingproject may also be used on the upper banksor within the gabions (Figure 4). However, thestability of vegetation or other upper bankprotection should be carefully analyzed toensure stability of the upper bank area. Afailure in the upper bank region can adverselyaffect gabion stability and lead to projectfailure.

CONSTRUCTIONA gabion project is installed by first smoothingthe area to be protected to the desired finalslope. The filter fabric and any required gravelfilter are then installed according to the designplans.


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Figure 4. Woody vegetation used withinthe gabion architecture (Coppin andRichards 1990)

The gabions are next assembled and tiedtogether, folded flat, stacked, and bundledby the supplier. They are bent into thedesign form, and all ends and diaphragmsare laced into place. The assembledgabions are then placed in their properlocation and laced (tied) to all surroundinggabions. It is important that all adjacentgabions be laced together. This preventsmovement and the failure of a project dueto the loss of one basket out of a protectedarea. Lacing should occur in accordancewith the manufacturer's recommendations.

After a sufficient number of gabions areassembled, filling can start. The fill should beplaced carefully in the gabions to preventdamage to the diaphragms and edges. Fillingshould be done in lifts of no more than 12 in.and some hand adjustment may be required toobtain a smooth attractive face. For gabionbaskets with heights greater than 12 in., tiewires or stiffeners are recommended after eachlift to prevent exposed faces from bulging (seeFigure 5).

Figure 5. Stiffener installation to prevent bulging faces (courtesy Hilfiker Retaining Walls)

After filling, the covers are placed on thegabions and secured with tie wires (laced).The gabions can be seeded with grass or othercover vegetation if the soil is intermixed with

the lifts of stone and if the hydrology is notlimiting. Again, large woody vegetation shouldbe avoided in the area protected by gabions.


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Care should be taken to determine soilproperties if the gabions are to be covered. Ifthe soil is saline or acidic, deterioration of thegabion wire can occur rapidly, leading toproject failure.

If the soil has a lower permeability than theunderlying bank material, water may not beable to move readily through the gabions,resulting in hydrostatic pressure behind thegabions. This can cause a sliding or rotationalfailure of the gabions. If the soil that is placedon the gabions is porous enough to allow easypassage of water through the gabion, it maynot retain enough water to support the desiredvegetation.

If a grass cover can be established overgabions, it is possible that the grass will remainstable during high flows since the root systemwill be firmly attached to the gabion mesh andunderlying rock fill. The problems of adequatemoisture and sufficient permeability of the soilneed to be carefully investigated.

While gabions may be able to support sometypes of vegetation, care should be used whenrecommending covering and filling the gabionswith intermixed soil and rock to supportvegetation.

OPERATION AND MAINTENANCEGabions need to be checked for broken wiresand repaired if necessary to protect stonecontained in the gabions from being removedby the force of water passing the cage.

Any large woody vegetation that has started togrow in the gabions should be removed andany damage to the gabions repaired. This mayinclude replacing lost stone and repairing anydamaged wire with wire similar to that used inthe construction of the cages.

The project area should be monitored for signsof erosion. If erosion is occurring at the toe ofthe gabion structures, measures should betaken to protect the gabions from undercuttingand subsequent failure. If water is eroding soilfrom behind a gabion wall, either the waterneeds to be diverted or measures need to betaken to eliminate the erosion of soil frombehind the gabions. This often occurs where

surface runoff enters the stream at a locationthat is protected by gabions.

The project should be monitored for any signsof geotechnical failure. If any of the gabionshave shifted or appear to be bulging away fromthe bank, measures should be taken toevaluate the seriousness of the problem. Ifproper geotechnical evaluations and measuresare taken during the design and constructionstages, there should be little chance of a majorproblem due to geotechnical failures.

APPLICABILITY ANDLIMITATIONSThe aesthetics of gabions are not as desirableas some other types of protective measuressuch as re-vegetation, but where the damages

and dangers associated with failures is high, orwhere serious erosion problems exist thatcannot be controlled with other methods,gabions are a viable alternative.

Caution should be exercised in using gabionsin areas where there is a high likelihood ofvandalism or damage from in-stream debrisincluding moving cobble, etc., that can harmthe wire by impact and scour. Under theseconditions, the wire containing the rock fill canbe damaged and the protection lost. Gabions

must also be protected against impact fromlarge woody debris and sharp objects. Thesematerials tend to distort and break the gabions.

If large woody vegetation is desired in an areato be protected by gabions, it may be possibleto use gabions or other methods such aspeaked stone toes to protect the lower bankand a vegetative treatment on the upper banks.This can provide for large woody vegetation onthe upper bank and yet provide highly effectiveprotection of the toe of the bank.

ACKNOWLEDGEMENTResearch presented in this technical note wasdeveloped under the U.S. Army Corps ofEngineers Ecosystem Management andRestoration Research Program. Technicalreviews were provided by Messrs. Jerry L.Miller and Hollis H. Allen, both of theEnvironmental Laboratory.


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POINTS OF CONTACTFor additional information, contact Dr. J.Craig Fischenich, (601-634-3449,[email protected] ), or the manager ofthe Ecosystem Management andRestoration Research Program, Dr. RussellF. Theriot (601-634-2733,[email protected] ). This technical noteshould be cited as follows:

Freeman, G. E., and Fischenich, J.C.(2000). "Gabions for streambank erosioncontrol," EMRRP Technical NotesCollection (ERDC TN-EMRRP-SR-22),U.S. Army Engineer Research andDevelopment Center, Vicksburg, MS .www.wes.army.mil/el/emrrp

REFERENCESCoppin, ., and Richards, . (1990). Use of vegetation in civil engineering. Butterworths,London.

Maynord, S., Hebler, M., and Knight, S. (1998).Users manual for CHANLPRO, PC programfor channel protection design, TechnicalReport CHL-98-20, U.S. Army EngineerWaterways Experiment Station, Vicksburg, MS.

Simons, D.B., Chen, Y.H., and Swenson, L.J.(1984). Hydraulic test to develop designcriteria for the use of reno mattresses, Reportprepared for Maccaferri Steel Wire Products,Ltd., Ontario, Canada. Civil Eng. Dept.,Colorado State Univ., Fort Collins, CO.

U.S. Army Corps of Engineers. (1994).Hydraulic design of flood control channels,Engineer Manual 1110-2-1601, Change 1, 30June, 1994, Washington, DC.

ABOUT THE AUTHORSGary E. Freeman is President of RiverResearch and Design, Inc. He holdsbachelor's and master's degrees in Agriculturaland Irrigation Engineering from Utah StateUniversity and a Ph.D. in Civil Engineering from

Texas A&M University. His research hasfocused on hydraulics, sedimentation, andhydraulic uncertainty.

J. Craig Fischenich is a Research CivilEngineer at the U.S. Army Engineer Researchand Development Center. He holds bachelor'sand Master of Science degrees, respectively, inCivil and Environmental Engineering fromSouth Dakota School of Mines andTechnology, and a Ph.D. in Hydraulics fromColorado State University. His research has

focused on stream and riparian restoration,erosion control, and flood damage reduction.


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TECHNICAL DATA SHEET Rev: 01, Issue Date 06.01.2007

GABIONGALVANIZED

Product DescriptionGabions are baskets manufactured from 8x10 double twistedhexagonal woven steel wire mesh, as per ASTM A975-97 (Figs.1, 2). Gabions are filled with stones at the project site to formflexible, permeable, monolithic structures such as retainingwalls, channel linings, and weirs for erosion control projects.The steel wire used in the manufacture of the gabion is heavilyzinc coated soft temper steel. The standard specifications ofmesh-wire are shown in Table 2.The gabion is divided into cells by diaphragms positioned atapproximately 3 ft (0.9 m) centers (Fig.1). To reinforce thestructure, all mesh panel edges are selvedged with a wirehaving a greater diameter (Table 3). Dimensions and sizes ofgalvanized gabions are shown in Table 1.Gabions shall be manufactured and shipped with allcomponents mechanically connected at the production facility.

WireAll tests on wire must be performed prior to manufacturing themesh. All wire should comply with ASTM A975-97, style 1coating. Wire used for the manufacture of Gabions and thelacing wire, shall have a maximum tensile strength of 75,000 psi(515 MPa) as per ASTM A641/A641M-03, soft temper steel.

Woven Wire Mesh Type 8x10The mesh and wire characteristics shall be in accordance withASTM A975-97 Table 1, Mesh type 8x10. The nominal meshopening D = 3.25 in. (83 mm) as per Fig. 2.The minimum mesh properties for strength and flexibility should

be in accordance with the following: Mesh Tensile Strength shall be 3500 lb/ft (51.1 kN/m)

minimum when tested in accordance with ASTM A975-97section 13.1.1.

Punch Test resistance shall be a minimum of 6000 lb (26.7kN) when tested in compliance with ASTM A975-97 section13.1.4 .

Connection to Selvedges should be 1400 lb/ft (20.4 kN/m)when tested in accordance with ASTM A975-97.

Lacing, Assembly and InstallationGabion units are assembled and connected to one anotherusing lacing wire specified in Table 3 and described in Fig. 4.MacTie preformed stiffeners or lacing wire can be used asinternal connecting wires when a structure requires more thanone layer of gabions to be stacked on top of each other. Internalconnecting wires with lacing wire shall connect the exposedface of a cell to the opposite side of the cell. Internal connectingpreformed stiffeners shall connect the exposed face of a cell tothe adjacent side of the cell. Preformed stiffeners are installedat 45 to the face/side of the unit, extending an equal distancealong each side to be braced (approximately 1 ft. (300 mm)). Anexposed face is any side of a gabion cell that will be exposed orunsupported after the structure is completed.Galvanized steel ring fasteners can be used instead of, or tocomplement, the lacing wire (Fig. 5).

Figure 1

Figure 2

The tolerance on the openingof mesh D being thedistance between the axis oftwo consecutive twists, isaccording to ASTM A975-97

Figure 3Example of gabion wall

Diaphragm

Back

Lid

End

End

Front

W

H

L

D

American Units


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Table 2Standard mesh-wire

Type D in. (mm) Tolerance Wire Dia in. (mm)

8x10/ ZN 3.25 (83) 10% 0.12 (3.05)

Figure 6

A

B

C

PneumaticSpenaxtool

Manual tool

All sizes and dimensions are nominal. Tolerances of 5% of the width,height , and length of the gabions shal l be permit ted.

Maccaferri reserves the right to amend product specifications without notice and specifiers arerequested to check as to the validity of the specifications they are using.

Lid closer

Figure 4

Figure 5

Lacing wire Rings

M a x

6 i n

.

( 1 5 0 m m

)

Open Closed

1.75 in.(44 mm)

0 . 7 5

i n .

( 1 9 m

m )

Nominal overlap of 1 in.(25 mm) after closure

Quantity RequestWhen requesting a quotation, please specify: number of units, size of units (length x width x height, see Table 1), type of mesh, type of coating.EXAMPLE: No. 100 gabions, 6x3x3, Mesh type 8x10,

Galvanized steel rings for galvanized gabions shall be inaccordance with ASTM A975-97 section 6.3.Spacing of the rings shall be in accordance with ASTM A975-97 Table 2, Panel to Panel connection, Pull-Apart Resistance.In any case, ring fasteners spacing shall not exceed 6 in. (150mm) (Fig. 4).The rings can be installed using pneumatic or manual tools(Fig. 6). For full details, please see the Gabion ProductInstallation Guide.

Table 3Standard wire diameters

LacingWire

MeshWire

Mesh Diameter in. (mm)

0.087(2.20)

0.120(3.05)

0.153(3.90)

Wire Tolerance() in. (mm)

0.004(0.10)

0.004(0.10)

0.004(0.10)

Minimum Qty/Zincoz/ft 2 (g/m 2)

0.70(214)

0.85(259)

0.90(275)

Selvedge Wire /PreformedStiffeners

L=Length ft (m) W=Width ft (m) H=Height ft (m) # of cells

6 (1.8) 3 (0.9) 3 (0.9) 2

9 (2.7) 3 (0.9) 3 (0.9) 312 (3.6) 3 (0.9) 3 (0.9) 4

6 (1.8) 3 (0.9) 1.5 (0.45) 2

9 (2.7) 3 (0.9) 1.5 (0.45) 3

12 (3.6) 3 (0.9) 1.5 (0.45) 4

6 (1.8) 3 (0.9) 1 (0.3) 2

9 (2.7) 3 (0.9) 1 (0.3) 3

12 (3.6) 3 (0.9) 1 (0.3) 4

4.5 (1.4) 3 (0.9) 3 (0.9) 1

Table 1Sizes for Gabions

Area Offices:

AZ, Phoenix KY, Lexington NM, AlbuquerqueCA, Sacramento MD, Williamsport PR, CaguasFL, Coral Gables NJ, Ramsey TX, Lewisville

website: www.maccaferri-usa.com

Headquarters:10303 Governor Lane BoulevardWilliamsport, MD 21795-3116Tel: 301-223-6910Fax: 301-223-6134email: [email protected]

MACCAFERRI INC.

2007 Maccaferri, Inc. Printed in USA


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Curlex

Staple Pattern GuideFor 8' wide Curlex Erosion Control BlanketsAdjust horizontal staple spacing for 4', 12', and 16' wide Curlex Erosion Control Blankets

= Staple Placement

B

3'

1.5'

3'

1.1 Staples/yd 2

A

3'

6'4'

0.6 Staples/yd 2

6'

C

4'

3'

2' 4'

4'

Critical channel points are circled.

1.9 Staples/yd 2

1. Recommended staples are a minimum 4biodegradable E-Staple , as provided by AmericanExcelsior Company, or 6 wire for cohesive soils and 6biodegradable E-Staple , as provided by AmericanExcelsior Company, or 8 wire for non-cohesive soils.

2. Adjust staple pattern so staples are placed in criticalchannel points (e.g. slope interface, channel bottom)as illustrated below:

Notes:

Slope ChannelApplication

4:1 3:1 1:1 6.0 lb/ft 2 (288 Pa) Shear Stress 15 ft/sec (4.6 m/sec) Velocity

Staple Pattern A B C C

3'

850 Avenue H East / Arlington, Texas 76011Phone 1-800-777-SOIL / Fax 817-385-3585 / www.Curlex.com

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Curlex

High Velocity

EROSION CONTROL BLANKETSPECIFICATION

PART I - GENERAL

1.01 Summary

A. The erosion control blanket contains excelsior wood fiber for the purpose of erosion control andrevegetation as described herein.

B. This work shall consist of furnishing and installing the erosion control blanket; including finegrading, blanketing, stapling, and miscellaneous related work, in accordance with these standardspecifications and at the locations identified on drawings or designated by the ownersrepresentative. This work shall include all necessary materials, labor, supervision, and equipmentfor installation of a complete system.

C. All work of this section shall be performed in accordance with the conditions and requirements of the contract documents.

D. The erosion control blanket shall be used to prevent surface erosion and enhance revegetation.Based on a project-by-project engineering analysis, the blanket shall be suitable for the followingapplications:

1. Slope protection2. Channel and ditch linings3. Reservoir embankments and spillways4. Culvert inlets and outfalls5. Dikes, levees, and riverbanks

1.02 Performance Requirements

A. Erosion control blanket shall provide a temporary, biodegradable cover material to reduce slopeand/or channel erosion and enhance revegetation.

B. Blanket performance requirements:

C factor: .022Shear Stress: 3.25 lb/ft 2 (156 Pa)Velocity: 11 ft/sec (3.4 m/sec)Functional Longevity*: 36+ months

*Functional Longevity varies from region to region because of differences in climatic conditions.


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1.03 Submittals

A. Submittals shall include complete design data, Product Data Sheets, Product Netting Information,MSDS, Staple Pattern Guides, Installation Guidelines, Manufacturing Material Specifications,Manufacturing Certifications, CAD details, and a Manufacturing Quality Control Program. Inaddition, the Manufacturer shall provide reference installations similar in size and scope to thatspecified for the project.

1.04 Delivery, Storage, and Handling

A. Erosion control blanket shall be furnished in rolls and wrapped with suitable material to protectagainst moisture intrusion and extended ultraviolet exposure prior to placement. Each roll shall belabeled with a date code identification, which allows for sufficient tracking of the product back todate of manufacturing and for quality control purposes.

B. Erosion control blanket shall be of consistent thickness with fibers distributed evenly over the entirearea of the blanket.

C. Erosion control blanket shall be free of defects and voids that would interfere with proper installation or impair performance.

D. Erosion control blanket shall be stored by the Contractor in a manner that protects them fromdamage by construction activities.

PART II - PRODUCTS

2.01 Erosion Control Blanket

A. Erosion control blanket shall be Curlex High Velocity (HV), as manufactured by AmericanExcelsior Company, Arlington, TX (1-866-9FIBERS).

B. Curlex HV erosion control blanket consists of a specific cut of 100% weed seed free Great LakesAspen curled wood excelsior with 80% of the fiber 6 inches in length. It is of consistent thicknesswith fibers evenly distributed throughout the entire area of the blanket. The top and bottom of each

blanket is covered with heavy duty UV stabilized polypropylene netting. Curlex HV is alsoavailable as QuickGRASS (Dyed Green), which also adds approximately four pounds to the totalweight of the blanket.

850 Avenue H East Arlington, Texas 76011Phone 1-800-777-SOIL Fax 817-385-3585 www.Curlex.com

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C. Erosion control blanket shall have the following material characteristics:

Width 4.0 ft (1.2 m) 8.0 ft (2.4 m)Length 100.0 ft (30.5 m) 50.0 ft (15.2 m)

Area 44.4 yd 2 (37.1 m 2) 44.4 yd 2 (37.1 m 2)Weight* 71.9 lb (32.6 kg) 71.9 lb (32.6 kg)

Fiber Count 15,500 per yd 2 ( 18,600 per m 2)

15,500 per yd 2( 18,600 per m 2)

Fiber Length (80% min.) 6.0 in ( 15.2 cm) 6.0 in ( 15.2 cm)Mass per Unit Area

( 10%)1.62 lb/yd 2

(0.88 kg/m 2)1.62 lb/yd 2

(0.88 kg/m 2)Net

OpeningsPolypropylene 0.75 in x 0.75 in(19.1 mm x 19.1 mm)

0.75 in x 0.75 in(19.1 mm x 19.1 mm)

TYPICAL INDEX VALUES**Index Property Test Method ValueThickness ASTM D 5199/ECTC 0.54 in (13.72 mm)Light Penetration ECTC Procedure 20%Resiliency ASTM D 1777/ECTC 53%Mass per Unit Area ASTM D 5261/ECTC 1.55 lb/yd

2

(841 g/m2

)MD-Tensile Strength Max. ASTM D 5035/ECTC 230.40 lb/ft (3.36 kN/m)TD-Tensile Strength Max. ASTM D 5035/ECTC 124.80 lb/ft (1.82 kN/m)MD-Elongation ASTM D 5035/ECTC 28.6%TD-Elongation ASTM D 5035/ECTC 36.7%Swell ECTC Procedure 48%Water Absorption ASTM D 1117/ECTC 194%Bench-Scale Rain Splash ECTC Method 2 SLR = 5.6 @ 2 in/hr Bench-Scale Rain Splash ECTC Method 2 SLR = 9.2 @ 4 in/hr Bench-Scale Rain Splash ECTC Method 2 SLR = 15.4 @ 6 in/hr Bench-Scale Shear ECTC Method 3 3.1 lb/ft 2 @ 0.5 soil lossGermination Improvement ECTC Method 4 616%

* Weight is based on a dry fiber weight basis at time of manufacture. Baseline moisture content of Great Lakes Aspen excelsior is 22%.

** SLR is the Soil Loss Ratio, as reported by NTPEP/AASHTO. Bench-scale index values should not be used for design purposes.

2.02 Staples

A. Staples shall be a minimum 4 biodegradable E-Staple , as provided by American Excelsior Company, or 6 wire for cohesive soils and 6 biodegradable E-Staple , as provided by AmericanExcelsior Company, or 8 wire for non-cohesive soils. All staples shall have a U-shaped top.

PART III - EXECUTION

3.01 Blanket Supplier Representation

A. Contractor shall coordinate with the blanket supplier for a qualified representative to be present at

the job site on the start of installation to provide technical assistance as needed. Contractor shallremain solely responsible for the quality of installation.

3.02 Site Preparation

A. Before placing erosion control blanket, the Contractor shall certify that the subgrade has been properly compacted, has been graded smooth, has no depressions, voids, soft or uncompacted areas,is free from obstructions such as tree roots, protruding stones or other foreign matter, and is seededand fertilized according to project specifications. The Contractor shall not proceed until all


W0707R1207

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unsatisfactory conditions have been remedied. By beginning construction, the Contractor signifiesthat the preceding work is in conformance with this specification.

B. Contractor shall fine grade the subgrade by hand dressing where necessary to remove localdeviations.

C. No vehicular traffic shall be permitted directly on the erosion control blanket.

NOTE: Topsoiling, seeding, and fertilizing is not included in this specification.

3.03 Slope Installation

A. Erosion control blanket shall be installed as directed by the owners representative in accordancewith manufacturer's Installation Guidelines, Staple Pattern Guides, and CAD details. The extent of erosion control blanket shall be as shown on the project drawings.

B. Erosion control blanket shall be orientated in vertical strips and anchored with staples, as identifiedin the Staple Pattern Guide. Adjacent strips shall be abutted or overlapped to allow for installation

of a common row of staples that anchor through the nettings of both blankets. Horizontal joints between erosion control blankets shall be sufficiently overlapped with the uphill end on top for acommon row of staples so that the staples anchor through the nettings of both blankets.

C. Where exposed to overland sheet flow, a trench shall be located at the uphill termination. Erosioncontrol blanket shall be stapled to the bottom of the trench. The trench shall be backfilled andcompacted. Where feasible, the uphill end of the blanket shall be extended three feet over the crestof the slope.

D. Slope erosion control blanket shall be overlapped by the channel erosion control blanket sufficientlyfor a common row of staples to anchor through the nettings of both blankets when terminating into achannel.

3.04 Channel Installation

A. Erosion control blanket shall be installed as directed by the owners representative in accordancewith manufacturer's Installation Guidelines, Staple Pattern Guides, and CAD details. The extent of erosion control blanket shall be as shown on the project drawings.

B. Erosion control blanket shall be installed parallel to the flow of water. The first roll shall becentered longitudinally in mid-channel and anchored with staples as identified in the Staple PatternGuide. Subsequent rolls shall follow from channel center outward and be overlapped to allowinstallation of a common row of staples so that the staples anchor through the nettings of both

blankets.

C. Successive lengths of erosion control blanket shall be overlapped sufficiently for a common row of staples with the upstream end on top. Staple the overlap across the end of each of the overlappinglengths so that staples anchor through the nettings of both blankets.

D. A termination trench shall be located at the upstream termination. Erosion control blanket shall bestapled to the bottom of the trench. The trench shall be backfilled and compacted.


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3.05 Quality Assurance

A. Erosion control blanket shall not be defective or damaged. Damaged or defective materials shall bereplaced at no additional cost to the owner.

B. Product shall be manufactured in accordance to a documented Quality Control Program. At aminimum, the following procedures and documentation shall be provided upon request:1. Manufacturing Quality Control Program Manual2. First piece inspection and documentation of products produced to assure component

materials and finished product tolerances are within manufacturer specifications.3. Additional inspections for product conformance shall be conducted during the run after the

first piece inspection.4. Moisture content readings recorded for each manufacturing day.5. Recorded weight of every erosion control blanket manufactured.6. Each individual erosion control blanket shall be inspected, weighed, and documented prior

to packaging for conformance to manufacturing specifications.7. Documentation and record retention for at least two years.

3.06 Clean-up

A. At the completion of this scope of work, Contractor shall remove from the job site and properlydispose of all remaining debris, waste materials, excess materials, and equipment required of or created by Contractor. Disposal of waste materials shall be solely the responsibility of Contractor and shall be done in accordance with applicable waste disposal regulations.

3.07 Method of Measurement

A. The erosion control blanket shall be measured by the square yard of surface area covered. Nomeasurement for payment shall be made for overlaps, fine grading, trenching, staples, or other miscellaneous materials necessary for placement of the erosion control blanket.

3.08 Basis of Payment

A. The accepted quantities of erosion control blanket shall be paid for at the contract unit price per square yard, complete in place.

Payment shall be made under:

Pay Item Pay UnitErosion Control Blanket Square Yards

Disclaimer: Curlex is a system for erosion control and revegetation on slopes and channels. American Excelsior Company (AEC) believes that the information contained herein to be reliable and accurate for use in erosion control and

re-vegetation applications. However, since physical conditions vary from job site to job site and even within a given jobsite, AEC makes no performance guarantees and assumes no obligation or liability for the reliability or accuracy of information contained herein for the results, safety, or suitability of using Curlex, or for damages occurring in connectionwith the installation of any erosion control product whether or not made by AEC or its affiliates, except as separately andspecifically made in writing. These specifications are subject to change without notice.


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Live Stake and JointPlanting for StreambankErosion Controlby Robbin B. Sotir and J. Craig Fischenich November 2007

Low Moderate High

Complexity

Low Moderate High

Environmental Value Cost

Low Moderate High

OVERVIEWThe live stake (LS) and joint planting (JP)soil bioengineering systems are unitsfabricated from live, woody plant materialbranches. Over time, the LSs are effective

for erosion control and the JP systemprovides reinforcement to slopes uponwhich rock has been placed. The LS and JPlive cut branches are expected to grow rootsand top growth, with the roots providingadditional soil reinforcement and surfacecover providing protection from runoff andstreamflow. The LS and JP units are usedfrom the baseflow elevation up the face ofthe streambank, acting principally to protectthe bank toe and face. In the case of theJPs, the root soil reinforcement serves to

augment bank protection. The LSs and JPsare also useful to improve erosion controland infiltration and support the riparianzone. Once top growth has developed, bothsystems have the potential to accumulatesediment (Figures 1-7).

Figure 1. Fabricating a live stake or jointplanting unit

Figure 2. Installing a live stake

Figure 3. Installing a joint planting

1 ERDC TN-EMRRP-SR-35


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Figure 4. An establishing live stake area

Figure 5. An establishing joint plantingarea

Figure 6. Development of a live stakeinstallation

Figure 7. Illustration of the developmentof a joint planting installation

The LS and JP may improve aquatic habitatby providing food and cover in the riparianzone and over the water when they areused in close proximity to the edge of thestream. Stone used at the base of the LS orwith JP produces substrates suited for an

array of aquatic organisms. Some of theseorganisms adapt to living on and within therocks and some attach to the leaves andstems. The leaves and stems may alsobecome food for shredders.

Species for LS and JP systems can beselected to provide color, texture, and otherattributes that add a pleasant, naturallandscape appearance. Such plants for LSand JP systems include willow ( Salix spp.),which tends to be the best from an

adventitious rooting perspective and isnormally an excellent choice. However otherspecies such as poplar (Populus spp. ),Viburnum spp., Hibiscus spp. , shrubdogwood (Cornus spp. ) and buttonbush(Cephalanthus ), also work well. Afterestablishment, the LS and JP systems canreduce non-point pollution by interceptingsediment and attached pollutants thatotherwise enter the stream from overbankflow areas.

PLANNINGThe first step in the planning process is todetermine whether an LS or JP system is anappropriate alternative to address theobserved and projected mechanisms ofbank loss. Questions that must beaddressed include the following inter-relateditems (not exhaustive):



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1. Is an LS or JP system an appropriatealternative given the magnitude of theerosion problem, e.g. its geomorphicand morphological characteristics?

2. Will the hydrology of the streamaccommodate an LS or JP system that

produces woody growth?

3. Are stream velocities and shearstresses permissible, and is the risk ofice and debris damage acceptable?

4. Will sediment accumulation be apositive or negative result for plantestablishment and survival?

5. Will there be enough sunlight and waterto support the desired system?

6. Are there riparian woody plants in areference reach or nearby similarsystem that can be used as a template(and perhaps material source) for theconstruction of an LS or JP system?

7. Will site conditions during constructionpermit installation?

8. Have risks, and specifically theconsequences of failure, beenconsidered and what are they (e.g.,what happens if the LS or JP systembecomes dislodged and materials movedownstream)?

9. What other erosion control devices ormaterials will be needed, such as gradecontrol in the bed, a filter fabric or stonein the JP or an erosion control fabric(ECF) on the bank?

10. Is the required construction seasonavailable?

11. Is depredation a potential problem, orcan it be controlled?

12. Are the costs acceptable?

CONSTRUCTION COSTSCosts for LS and JP projects arecomparable to those for other bank

stabilization techniques. Following are Year2001 cost ranges for LS and JP projectsbased on the authors experiences. Theseinclude profit margins and contingencyfactors on contractor bid projects.

The LS costs range from $3 to $10 each,

while the JP costs range from $6 to $15each. These prices include harvesting,transportation, handling, fabrication, andstorage of the live cut branch materials.Costs for other system elements (e.g.riprap) and bank reshaping are not included.Costs may vary with access, availability oflive material, time of year and prevailinglabor rates. Fabrication of the LS or JP issimple and is performed either just prior toinstallation in moist climates and a weekprior in dry areas. In dry areas, soaking the

living stakes for a week in water improvessurvival. Both LS and JP structures may befabricated in custom length for specialneeds. Installation is also relatively easy, aslarge equipment is not required except toslope back the bank. Fabrication andinstallation costs are usually low.

SITE CONSIDERATIONSA site suited to LS or JP treatments requiresa hydrologic regime that 1) keeps the invertof the stake wet during most of the growingseason where the establishment of woodyplants are desirable; 2) allows the roots toreach the water table or vadose zone duringmost of the growing season; and 3) sustainsflows sufficient to keep woody plantsgrowing well but not large and long-durationof flows so as to exceed the plants floodtolerance. Given these requirements,streams best suited have perennial flowsand are small to moderate in size, althoughthe authors have successfully applied thesetreatments on a wide range of systems.

Some variation in water surface elevationassociated with baseflow is acceptable.However, the roots must have access towater.

The second most important factor in siteselection is choosing a site that is notsubject to massive amounts of sedimentmovement that could smother plantsestablishing on the bank. After they become



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established, however, LS and JPs areeffective in trapping soils from stream flows.They also establish conditions forsubsequent colonization or planting, mostoften within the captured sediment. WhenLS's are used along a stream system,installation should follow the stabilization ofthe upper bank face using an appropriateerosion control fabric.

A site suited to LS or JP treatments musthave adequate soil (growing medium)available to allow for root penetration. Leanclays and highly compacted soils inhibit rootgrowth and generally result in poor success.Soil pH should be in the range of 68, andthe soils should have sufficient nutrients orbe augmented with a slow release fertilizer.Inoculation of the soils with mychorrizae to

stimulate root growth is often helpful.

Other important considerations in siteselections are shade conditions, type ofsubstrate in which they will be placed, andtheir relation to the channel thalweg. Mostplants that are desired for establishment areshade intolerant and require some sunlight.As a general rule, moderate sunlightexposure should exist for LS and JPstructures. There are exceptions whereshade-tolerant plants (e.g. viburnum) can be

used , but success is often poor. Consult theNatural Resources Conservation Serviceoffices for information on local plantssuitable for the area of interest.

A cobble substrate or one laden withinterspersed rock can require specialequipment or materials to achievepenetration. LSs and JPs may be installed1.5 to 4 ft deep and diameters in the 1- to2-in. range are typically most successful, sodriving these stakes into a hard substrate

can be problematic. For highly erodiblebank materials, LS should be protected witha stone toe buttress to prevent scour andundercutting and an erosion control materialto prevent surficial erosion.

DESIGNPrimary Design Considerations Depth of erosion must be in the range of 1to 3 in. for the LS system to be an effectiveimmediate erosion control method whenused with erosion control fabric. Elevation ofthe LS and JP systems must be suited tothe vegetation for which they providesubstrate. In general, the LS or JP must beat an elevation that permits absorption ofwater from groundwater seepage from thebank to prevent desiccation of thevegetation. However, it must not be placedso low as to inundate the vegetation beyondits flood tolerance. When willow branches orother woody plants are used in LS or JPconstructions, their basal ends are insertedwell into a moist zone within the bank(Figures 2 and 3). There is no requirementfor periodic wetting. In these cases, LS's areintended primarily to provide sediment anderosion control after the woody vegetationhas become established.

The LS's or JPs are typically installed in arandom pattern or in rows and spaced apartaccording to slope and soil conditionsillustrated in Tables 1 and 2. On moistseeping banks, more LS's may be used toassist in moisture depletion.

Table 1. Live Stake Spacing

Spacing feet O.C.

SoilsSlope Steepness Cohesive Non-Cohesive

1:1 2 to 3 N/A2:1 3 to 4 2 to 33:1 or flatter 4 to 6 3 to 5

O.C. = On Center Assumes stable slopeNote: Recommended to be used with an erosioncontrol fabric



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Table 2. Joint Planting Spacing

Spacing Feet O.C.

SoilsSlope Steepness Cohesive Non-Cohesive

1.5:1 N/A N/A2:1 1.5 to 3 1.5 to 2

3:1 or flatter 3 to 5 2 to 4 O.C. = On Center Assumes stable slopeNote: All are recommended to be used with loosedumped riprap or evenly placed no deeper that 18with filter fabric or filter stone in non-cohesive soils.

Only limited data have been collected forshear or velocity tolerances of LS and JPstructures. Available data come largely fromempirical information collected from

constructed projects (Tables 3 and 4).Designers should exercise caution inconsidering limiting velocity or shear stresscriteria. Failure of LS or JP structures canbe attributed to several mechanisms,notably flanking, and undercutting.

Table 3. Live Stakes in Bare Soil BeforeEstablished

Soils Velocity, ft/sec Shear, lb/ft

Silts .05 .001Sands .5 .01

Large Gravel 2 .5Large Cobble 4 2Firm Loam 2.5 .08Stiff Clays 3 - 4 .2512 RoundedRiprap

6 4

Table 4. Live Stakes with Erosion ControlFabrics Prior to and After Establishment

Fabric Velocity, ft/sec Shear, lb/ft

JuteBefore Est. 1 2.5 .45After Est. 3 7 2.1 3.1

Woven Coir 700gm wt.Before Est. 3 5 2 2.5After Est. 3 - 10 2.1 3.1

Success for both LSs and JPs requires thatprotection be provided against undercuttingand flanking of the treatment. For toe andflank protection, rock protection should bedesigned for velocities and shear stressesexceeding allowable limits for the soils androck underlying and within the LS or JP.Fischenich (2001) presents these limits.Angular rock is recommended and shouldbe sized in accordance with the U.S. ArmyCorps of Engineers (1994) specificationsdepending on anticipated velocities andshear stress.

Flank protection can also be aided bykeying the ends of the LS or JP systemsinto the banks at both ends and protectingthe flanks with a rock protection. Key endswell into the bank with rock on the upstream

side, which is also keyed into the bank. Forbanks susceptible to significant erosion,keys or refusals extend farther into thebank.

Table 5. Threshold Conditions

ClassName

DS (IN)

(DEG) C

C (LB/SF)

VC (FT/S)

Boulder

Very large >80 42 0.054 37.4 25

Large >40 42 0.054 18.7 19Medium >20 42 0.054 9.3 14

Small >10 42 0.054 4.7 10Cobble

Large >5 42 0.054 2.3 7

Small >2.5 41 0.052 1.1 5

Gravel

Verycoarse

>1.25 40 0.050 0.54 3

Coarse >0.63 38 0.047 0.25 2.5

Other Design Considerations Other design considerations, including thelength of bank and face width being eroded,will determine the length of the treatmentneeded.

Eroded banks are not always conducive toimmediate LS or JP installation and typicallyrequire reshaping or filling treatment toaccommodate the use of LS or JPinstallation. If fill is required, rock fill mixedwith other substrate suitable for plant growth



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will be needed for LS. Rock alone is oftenused to prevent undercutting. Fill will needto be calculated based on cross-sectionalarea of the bank times the length of reach.Size of rock and appropriate gradationshould be determined from U.S. ArmyCorps of Engineers (1994).

FABRICATIONLSs and JP's are fabricated using fresh,live cut branch material that roots easilyfrom cuttings, typically harvested from anatural stand within 40 miles of the projectsite. The materials should be dormant andfree of splits, rot, disease, and insectinfestation. The rootable material that is tomake up the stakes should be selected withconsideration given to the type that existson adjacent areas. Native naturally growingplants such as willow or shrub dogwoodspecies work well and are usually available.

Material should be harvested from plantsthat are at least 2 years old. Harvesting oflive material should leave at least one thirdof the parent plant intact. Live cut branchesshould be from 0.5 to 1.5 in. in diameter, 1.5to 3 ft in length for LSs, and 0.75 to 2 in. indiameter and 2.5 to 3.5 ft in length for JPs.Cleanly remove all side branches. Thebottom or basal end of the cuttings shouldbe cleanly cut at an angle and the top endshould be cut square (flat).

The LSs are prepared in bundles of 10 to25 with the growing tips oriented in thesame direction. Age, size, and speciesshould be mixed when bundling to reflectthe desired distribution of installed plants.Harvested material should not be allowed todry. If it is necessary to harvest materialsignificantly before installation, the stakesshould be stored in wet burlap at

approximately 33 to 40 deg F. Alternatively,one third of the basal end could be stored incold water.

CONSTRUCTIONThe primary considerations concerningconstruction with an LS and JP are bankpreparation, soil types, moisture availability,and physical handling and installation of livestakes. Stakes should be soaked for a

minimum of 24 hr in cool, aerated waterprior to installation. Rocks or burlap sackscan be used to anchor the material in thestream to prevent it from floating away.Optimum time for soaking is 5 to 7 days butthey can also be planted the same day asharvested if they are watered.

Installing LSs or JPs may be as simple astamping the live cutting directly into theground with a dead blow hammer. If theground is hard or rocky, it may require apunch bar or stake to create a pilot hole.The hole should be two-thirds to three-fourths the length of the stake and ofapproximately the same diameter. If thearea is dry, it may be advisable to water thehole prior to installing the stake. Stakesmust be installed with the basal end down.

Stakes that are split during installationshould be removed and replaced. Careshould be taken not to damage thecambium layer of the stakes.

At least two buds or bud scars should bepresent above the ground, so an installedLS generally has 3 to 6 in. left exposedabove ground. Greater lengths of exposedstakes increase desiccation and reducesurvival. Good soil-to-stem contact isrequired for proper rooting, so it may be

necessary to add soil slurry to pilot holes.The ground around the LS is typically foottamped to ensure good soil contact. JPsmay be installed leaving a few inches abovethe riprap rock, but are generally cut flushwith the top of the riprap. When live stakesare installed into erosion control fabric, thewoven threads must be spread apart or asmall hole cut/punched into the fabric. Thehole should be as small as possible topreserve the fullest bank protectionavailable from the erosion control fabric.

Time of Year LS or JP need to be harvested in thedormant season for the best results and forthe most cost-effective project. They aregenerally best installed during the dormantseason as well, but can be installed anytime of the year if the cuttings are properlystored (at 3040 deg F, in a low moistureenvironment, and with no direct sunlight



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exposure). Installation into frozen or heavilyfrosted soils is difficult, at best, so late falland early spring are the preferredinstallation times throughout most of theUnited States.

OPERATION ANDMAINTENANCEOperation and maintenance requirements ofany soil bioengineering treatment will varydepending on the stream system and itsassociated parameters, such as velocity,flood frequency, flood stage, timing, andfuture planned use. In any case, beprepared, at least early in the project life, torepair or augment the systems until thevegetation becomes well established.Minimally, inspection should occur aftereach of the first few floods and/or at leasttwice a year the first year and once a yearthereafter, preferably after the predominantflood season.

Immediately repair observed undercuttingand flanking of the treatment and any othersubstantial scour evidence. Examine thelive cuttings in the LS or JP for adequatesurvival and growth and absence ofdisease, insect, or other animal damage(e.g., grazing, trampling, digging, eating,and cutting). Successful plants will growvigorously and spread their roots into thesurrounding substrate.

If animal or human trampling damage isevident or the plants are being removed oreaten by waterfowl or beavers, preventativemeasures such as exclosures may berequired. Such exclosures, especially forwoody plants, may only need to be useduntil the vegetation is well established (1 to3 years).

Assuming the LS and/or JP remains inplace and vegetation becomes establishedthrough the development of growth from thelive cutting or through plant developmentfrom natural invasion, maintenancebecomes less over time.

Fish and aquatic invertebrate sampling isalways recommended both beforeinstallation to gather base information and

after the installation has becomeestablished (1 to 3 years), to determinehabitat improvement effectiveness.

APPLICABILITY ANDLIMITATIONSTechniques described in this technical noteare generally applicable where primaryobjectives for streams include habitatdiversity, erosion control, water qualityimprovement, and aesthetics, including adiversity of riparian plants along thestreambank. LS or JP systems are expectedto establish on a wide range of streamshaving fairly constant and consistent baseflows as well as ephemeral stream systems.However, vegetation may tend to dry outand die in extreme conditions and whereinstallations are not deep enough to allowroots to reach adequate moisture. This maybe especially true for JPs. Streams shouldnot have excessive sediment loads that maycompletely cover and smother theestablishing LS or JP. Some caution is alsoneeded when selecting the species for LSor JP.

Exercise caution in using JP or LS without arock protection or other hard material whenstream velocities at the bank exceed criticalthresholds for underlying soils.

Trampling and grazing of LS can bedetrimental from a living perspective. Usemay be limited in areas where cattle grazingis not restricted. Note that due to safety, livestakes are not recommended over the bankin high traffic areas where people may tripand fall on them.

Consider the time of year when installingLSs or JPs as well as water elevation.Consider consequences of failure if an LSor JP is flanked and washed downstreamand if the failure is likely to create hazardsthat otherwise would not occur (e.g.,trapping debris and causing undesired localscour, current deflection, and damming).



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ACKNOWLEDGEMENTSResearch presented in this technical notewas developed under the U.S. Army Corpsof Engineers Ecosystem Management andRestoration Research Program. Technicalreviews were provided by Messrs. JimHenderson and Jock Conyngham of theEnvironmental Laboratory, U.S. ArmyEngineer Research and DevelopmentCenter.

POINTS OF CONTACTFor additional information, contact theauthors, Robbin B. Sotir (770-424-0719),[email protected] ) or Dr. J. CraigFischenich, (601-634-3449,[email protected] ),or the manager of the EcosystemManagement and Restoration ResearchProgram, Glenn Rhett (601-634-3717,[email protected] ). Thistechnical note should be cited as follows:

Sotir, R. B., and J. C. Fischenich.2007. Live stake and joint planting for streambank erosion control .EMRRP Technical Notes Collection.ERDC TN-EMRRP-SR-35.Vicksburg, MS: U.S. Army EngineerResearch and Development Center.www.wes.army.mil/el/emrrp.

REFERENCESFischenich, C. 2001. Stability thresholds for stream restoration materials . EMRRPTechnical Notes Collection. ERDC TN-EMRRP-SR-29. Vicksburg, MS: U.S. ArmyEngineer Research and DevelopmentCenter. www.wes.army.mil/el/emrrp .

U.S. Army Corps of Engineers. 1994.Hydraulic design of flood control channels .Engineer Manual 1110-2-1601, Change 1,30 June 1994. Washington, DC.
mailto:[email protected]://www.wes.army.mil/el/emrrphttp://www.wes.army.mil/el/emrrpmailto:[email protected]

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