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129LOW-VOLUME ROADS BMPS:

Chapter 13

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EROSION CONTROL on roads is fundamental forthe protection of water quality (Photo 13.1).Soil stabilization and erosion control practicesare needed and should be used in areas where soil isexposed and natural vegetation is inadequate. Bareground should be covered, typically with grass seedand some form of matting or mulch. This will helpprevent erosion and subsequent movement ofsediment into streams, lakesand wetlands. This movementof sediment can occur duringand after road construction,after road maintenance, duringlogging or mining activities, asthe road is being used, if a roadis closed but not stabilized, orfrom poor land managementpractices near the road (Photo13.2). Roughly half of theerosion from a loggingoperation, for instance, comesfrom the associated roads.Also, most erosion occursduring the first rainy seasonafter construction.

Erosion control measuresneed to be implemented im-mediately following construc-

Erosion control -- one of the best, most inexpensive waysto protect the road and the environment. Just do it!

Photo 13.1Photo 13.1Photo 13.1Photo 13.1Photo 13.1 Do not leave disturbed or barren areas exposed to rain-drops and runoff. Use erosion control measures to protect the area andprotect water quality.

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tion and every time an area is disturbed. Soil erosionprediction models such as the Water Erosion Pre-diction Project (WEPP) or Unified Soil Loss Equa-tion (USLE) can be used to quantify erosion andcompare the effectiveness of various erosion con-trol measures. Concentrated water flow can beginas minor sheet flow, produce rills, and eventually re-sult in major gully formation (See Chapter 14).

LOW-VOLUME ROADS BMPS:130

Photo 13.2Photo 13.2Photo 13.2Photo 13.2Photo 13.2 Erosion on a slope adjacent to a highway due to lack ofvegetation or poor land use practices. Note that vegetation ispreventing erosion next to the highway.

Erosion control practices in-clude surface armoring andground cover with netting (Photo13.3), vegetative material or slash(Photo 13.4), rock, and so on; in-stalling water and sediment con-trol structures; and mulching,seeding, and various forms ofrevegetation, as seen in Figures13.1 through Figure 13.4. Effec-tive erosion control requires at-tention to detail, and installationwork requires inspection andquality control.

Physical methods includesuch measures as armored ditches(Photo 13.5), berms, wood chips,ground cover mats, and silt orsediment fences (Photo 13.6).These control or direct the flowof water, protect the ground sur-face against erosion, or modify thesoil surface to make it more resis-tant to erosion (Photo 13.7).

Vegetative methods, usinggrasses, brush, and trees, offer

ground cover, root strength, andsoil protection with inexpensiveand aesthetic natural vegetation,as well as help control water andpromote infiltration (Photo 13.8).Ideally, vegetation should be se-lected for good growth proper-ties, hardiness, dense groundcover, and deep roots for slope

stabilization. Local native specieshaving the above mentioned prop-erties should be used. Howeversome grasses, such as Vetiver,have been used extensively world-wide because of their strong, deeproots, adaptability, and non-inva-sive properties (Photo 13.9).

Biotechnical methods suchas brush layering, live stakes, andcontour hedgerows (Figure 13.4)offer a combination of structureswith vegetation for physical pro-tection as well as additional long-term root support and aesthetics(Photo 13.10).

An Erosion Control Plan anduse of erosion control measuresshould be an integral part of anyroad construction or resource ex-traction project. Most disturbedareas, including landings, con-struction storage areas, skidroads, road fills, some road cuts,drainage ditches, borrow pits, theroad surface and shoulders, andother working areas should re-

Photo 13.3Photo 13.3Photo 13.3Photo 13.3Photo 13.3 Cover fill slopes, work areas, and other exposed soilareas with straw, netting, rock, or other material to protect theground and promote vegetative growth.


A. Description of Project1. Project Objectives2. Project Location3. Description of Local Environment

B. Planning1. Site Analysis

a.Climate and Microclimateb.Vegetation Optionsc.Soils and Fertility

2. Developing the Revegetation Plana.Suitable Plant Speciesb.Soil and Site Preparationc.Aesthetics vs. Erosion Control Needsd.Use of Local Native Species

C. Implementation1. Planting MethodsCuttings and Transplants

a.Tools and Materialsb.Planting Holes and Methods

2. Planting MethodsSeeding and Mulchinga.Hand Broadcasting or Hydroseedingb.Range Drillsc.Type / Quantity of Seedd.Type / Quantity of Mulch and Fertilizere. Holding Mulch with Tackifiers or Netting

3. Plant Protectiona.Wire Caging around Plantsb.Fencing Around the Entire Site

4. Maintenance and Care After Plantinga.Irrigationb.Weed Controlc.Fertilization

5. Biotechnical Planting Methodsa.Wattlingb.Brush Layering or Brush Mattingc.Live Stakes

D. Obtaining Plants and Handling of Plant Materials1. Timing and Planning

a.Fall versus Spring Plantingb.Summer Plantings

2. Types of Plant Materialsa.Cuttingsb.Tublingsc.Other Container Plants

3. Hardening-off and Holding Plants (Acclimatizing)4. Handling Live Plants and Cuttings

TTTTTaaaaabbbbble 13.1le 13.1le 13.1le 13.1le 13.1

Key Elements of an Erosion Control andRevegetation Plan for Road Projects

ceive erosion control treatment. Itis more cost effective and efficientto prevent erosion than to repairthe damage or remove sedimentfrom streams, lakes, or ground-water.

Elements of an Erosion Con-trol and Revegetation Plan includeproject location and climate, soiltypes, type of erosion controlmeasures, timing of implementa-tion of the vegetative erosion con-trol measures, source of seeds andplants, and planting methods.Table 13.1 presents the many as-pects of planning, implementation,and care involved in an ErosionControl Plan for roads projects.

PRACTICES TOAVOID

Disturbing unnecessarilylarge areas.

Leaving native soil un-protected against ero-sion after new construc-tion or ground distur-bance.

Earthwork and road con-struction during periodsof rain or the winter.


Grass seedand mulch

Aggregatesurfacedroadbed

Old landing orconstructionwork area

Sedimentcatchmentbasin

Logging slashor woodymaterial spreadover the area

Various erosion control ground coversinclude seeding and straw mulch,grasses and other mulch, vegetation,rock, slash, chips, and leaves.

Deep rootedvegetation forslope stabilization

Woody slash

Grasses

Aggregate roadsurfacing orscarification, seedand mulch forclosed roads

Vegetative ground cover

Grasses or othervegetation

Cross-section

Perspective View

Vegetative contourhedgerow or wattles

FFFFFigurigurigurigurigure 13.1 e 13.1 e 13.1 e 13.1 e 13.1 Use of vegetation, woody material and rock for erosion control and ground cover.(Adapted from Wisconsins Forestry BMP for Water Quality, 1995)


Photo 13.4 Photo 13.4 Photo 13.4 Photo 13.4 Photo 13.4 A disturbed workarea covered with woodymaterial such as brush fromclearing or logging slash forerosion control . Ensure thatthe material is well mashedonto the ground.

Photo 13.5 Photo 13.5 Photo 13.5 Photo 13.5 Photo 13.5 A roadside ditcharmored with graded rock(riprap) for erosion control.

Photo 13.6 Photo 13.6 Photo 13.6 Photo 13.6 Photo 13.6 Sediment controlfences (silt fences), live vegeta-tive barriers, or brush fencescan all be used to controlsediment movement on slopes(also see Photo 6.6).


Photo 13.7 Photo 13.7 Photo 13.7 Photo 13.7 Photo 13.7 Rock armoring,placed on a very erosive soil fillslope adjacent to a creek, usedfor durable, permanent erosioncontrol.

Photo 13.8 Photo 13.8 Photo 13.8 Photo 13.8 Photo 13.8 Seed and mulch(cover for seed protection andmoisture retention) applied tothe ground surface to promotegrass growth on barren areas,closed roads, and on erosivesoils.

Photo 13.9 Photo 13.9 Photo 13.9 Photo 13.9 Photo 13.9 Use of Vetivergrass for slope stabilization anderosion control. Choose vegeta-tion that is adapted to the site,has strong roots, and providesgood ground cover. Ideally, usenative species.


a. Hay Bales (or bundles of grass)

b. Silt Fences

Leave no gapsbetween bales.

Staked and entrenchedstraw bale. (Use twostakes per bale.)

Bales keyed(buried )10 cm deepinto soil.

Overland

Flow(runo

ff)

Tampedsoil

Runoff

Filter fabricsilt fence

Compactedbackfill intrench

10cm

Runoff

FFFFFigurigurigurigurigure 13.2ae 13.2ae 13.2ae 13.2ae 13.2a Sediment control structures using hay bales or silt fences. Note that hay bales mustbe installed correctly and keyed into the ground! (Adapted from Wisconsins Forestry BMP forWater Quality)

10 cm

Filter fabricsilt fence

Stake

Note: Problems can develop from water running between and underhay bales. Install them carefully. Long-term structures must be periodi-cally cleaned and maintained.


c. Brush Barrier

Brush Fence (buried 10 cm deep into soil).

Outlet for Cross-Drain

or Outsloped road

Barrier constructed of smallbrush and limbs pushed tothe ground at the toe of thefill slope

OverlandFlow

FFFFFigurigurigurigurigure 13.2b e 13.2b e 13.2b e 13.2b e 13.2b Sediment control structures using brush barriers and brush fences.


Ground protected withgrasses

Ditch armoredwith rock,concrete,masonry or grass

Berm protected withgrasses and brush

30-50 cmDeep

30 cmWide

a. Water Control with Ditches and/or Berms

FFFFFigurigurigurigurigure 13.3 e 13.3 e 13.3 e 13.3 e 13.3 Water control structures.

NO YESMasonry orrock walls

Broken byrunoff

Vetiver grasscontour hedgesand rockwalls

b. Water Control with Vegetative Barriers(and Terracing) (Adapted from Vetiver, 1990)

Road

Road

Fieldcrops

Fieldcrops

Fieldcrops

Masonrywall

Field crops orroad

Vetiver grass hedge

(Detail)

Deep roots forstabilization


Photo 13.10 Photo 13.10 Photo 13.10 Photo 13.10 Photo 13.10 Use of grasses,planted on contour, to providesurface slope stabilization anderosion control on a steep roadcut.

Photo 13.11 Photo 13.11 Photo 13.11 Photo 13.11 Photo 13.11 Live vegetativebarriers (contour hedgerows),using Vetiver, other grasses, orvegetation, located on contourto prevent down-slope erosionfrom barren or disturbed areas.

Photo 13.12 Photo 13.12 Photo 13.12 Photo 13.12 Photo 13.12 A local nursery,developed in conjunction with aconstruction project, to providea source of plants and growappropriate (preferably native)vegetation for the erosioncontrol work.


Develop a project ErosionControl Plan to addressinterim and final erosioncontrol needs, specificmeasures, and how toimplement or install thosemeasures. Develop typicaldrawings for sediment traps,sediment fences, brushbarriers, ground cover,check dams, armoredditches, and biotechnicalmeasures.

Disturb as little ground areaas possible, stabilize thatarea as quickly as possible,control drainage through thearea, and trap sediment on-site.

Conserve topsoil with its leaflitter and organic matter, andreapply this material to localdisturbed areas to promotethe growth of local nativevegetation.

Apply local, native grassseed and mulch to barrenerosive soil areas or closedroad surfaces. Mulchmaterial may be straw, woodchips, bark, brush, leavesand limbs, shredded paper,or gravel. (Figure13.1).

Apply erosion controlmeasures before the rainyseason begins and after each

season of construction,preferably immediatelyfollowing construction.Install erosion controlmeasures as each roadsection is completed.

Cover disturbed or erodingareas with limbs, tree topsand woody debris such aslogging slash placed oncontour and mashed down toachieve good contact withthe soil (Figure 13.1).

Install sediment controlstructures where needed toslow or redirect runoff andtrap sediment until vegeta-tion is established. Sedi-ment control structuresinclude windrows of loggingslash, rock berms, sedimentcatchment basins, strawbales, brush fences, and siltfencing (see Figures 13.1,13.2a and 13.2b).

Control water flow throughconstruction sites or dis-turbed areas with ditches,berms, check structures, livegrass barriers, and rock(Figure 13.3).

Place windrows of loggingor clearing slash along thetoe of roadway fill slopes(See Low-Volume RoadsEngineering, Figure 4.2).

Stabilize cut and fill slopes,sliver fills, upland barrenareas, or gullies with brushlayers, rock structureswith live stakes, vegetativecontour hedgerows (Photo13.11), wattling, or otherbiotechnical measures(Figure 13.4).

Maintain and reapplyerosion control measuresuntil vegetation is success-fully established. Do soilchemistry tests if necessaryto determine available soilnutrients.

Use fertilizers in areas ofpoor, nutrient deficientsoils to promote fastergrowth and better erosioncontrol. Fertilizer shouldbe used only if needed.Add water or irrigationonly if necessary to ini-tially establish vegetation.

Develop local plantsources and nurseries forvegetative erosion controlmaterials. Use local nativespecies whenever possible(Photo 13.12). Selectspecies appropriate for theuse, the site, and thebioregion.

RECOMMENDED PRACTICES


Vetiver grasscontour hedges

a. Contour HedgesFor Erosion Control andSlope Stabilization (Adaptedfrom Vetiver, 1990)

b. Brush Layering(for Stabilization of Gullies and Slides)

Live stakes1.5-5.0 cmdiameter placedin layers

Compacted fill15-20 cm thicklayers

Road

Sprouts with roots

Fill

Rock wall and face1.5-3.0 m high

Live stakes 1-3 cmin diameterRoad bed

0.3-0.5 m

c. Live Retaining WallsConstructed with Rock orGabions and Vegetation

Base of a gullyor slump area

FFFFFigurigurigurigurigure 13.4e 13.4e 13.4e 13.4e 13.4 Biotechnical slope stabilization measures.

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