Stream Stabilization Practices

Virginia Stream Restoration & Stabilization Best Management

Practices Guide

Resources

• User Friendly: – Virginia Stream Restoration & Stabilization Guide http://dcr.virginia.gov/stormwater_management/documents/streamguide.pdf – Maryland’s Waterway Construction Guidelines http://www.mde.state.md.us/assets/document/wetlandswaterways/mgwc.pdf – U.S. Forest Service: Soil Bioengineering Guide 2002 www.Fs.fed.us/publications/soil-bio-guide

• Technical:

– NRCS National Engineering Handbook Part 654 – NRCS Engineering Field Handbook Chapter 16 http://wildfish.montana.edu/manuals/EFH-Ch16.pdf

Considerations

• Goals and Objectives – Desired Land Use – Vegetation Compatibility – Aesthetics versus Function

• Scope of the Problem

– Lateral Migration (Widening of Channel) – Vertical Down Cutting (Deepening of Channel) – Localize Scour (Scallop Shaped or Overhanging Vegetation)

• Planning & Design

– Private Engineer/Consultant – Contractor Experience – Cost Benefit and Financial Assistance

Lateral Migration (Widening)

Vertical Down Cutting (Deepening)

Local Scour

Bank and Toe Protection Practices

• 1.1 Cedar Tree Revetments

• 1.2 Rootwad Revetments

• 1.3 Stacked Stone

• 1.4 Boulder Revetment

• 1.5 Rock-Toe Revetment

• 1.6 Live Crib-Wall

• 1.7 Interlocking Concrete Jacks

1.1 Cedar Tree Revetment

Limitation: - Material Availability - Wire Anchoring Must be

Installed Correctly - Not for Streams with Vertical

Instability - Sediment Loads are needed

Appropriate Uses: - Localized Areas of Toe Scour - Medium or Small Streams - Used in Conjunction with Bank

Stabilization Measures

1.2 Root-wad Revetment

Limitations: - Material Availability - Short Life Span - Not Always Aesthetically Pleasing - Smaller Streams Problematic - Vulnerable to Vertical Downcutting

Appropriate Uses: - Outside Bend - Used as a Component of an Integrated

Bank Treatment - Useful in Conjunction with Grade Control - Useful for Localized Scour Areas

1.3 Stacked Stone

Limitations: - Heavy Equipment Needed - Solid Stones Preferred - Solid Stone Difficult to Find - High Cost

Appropriate Uses: - Highly Durable Bank Protection

Required due to Soils - Stream Bank Slope Greater than 1:1 - Vegetative Establishment Low or

Undesired

1.4 Boulder Revetment

Limitations: - Heavy Equipment - Smaller Streams may be Constricted - Higher Costs than 1.5 Rock Toe Revetments

Appropriate Uses: - Rigid Toe Protection Desired - Local Supply Available - Toe Protection in Integrated

Bank Treatment - Toe of Steep Stream Banks

1.5 Rock Toe Revetment

Limitations: - Not used on Actively Incising Streams - Not Aesthetically Pleasing

Appropriate Uses: - Rigid Toe Protection Desired - Toe Protection in Integrated Bank Treatment - Easy Assess for Dump Truck

1.6 Live Crib-Wall

Limitations: - Maximum Height of 7-8 Vertical Feet - Not for Large Earth Stresses - Requires Additional Toe Protection - Accessible to Equipment - Suitable to Vegetation Growth - Requires Successful Establishment of

Vegetation

Appropriate Uses: - Steep Bank Slopes are Required - Both Structural and Vegetative Practice

Required - Stabilize Toe of Cut or Fill Slopes

1.7 Interlocking Concrete Jacks

Limitations: - Units Break During Transport - May Break if Impacted by Debris - Accessible to Heavy Equipment - Intensive Manual Labor

Appropriate Uses: - Permanent Rigid Toe Protection - Toe Protection Integrated with Bank Treatment - Site limits Dump Trucks - Can Incorporate Vegetative Plantings

Bank Stabilization Practices

• 2.1 Natural Fiber Rolls

• 2.2 Live Soil Lifts

• 2.3 Natural Fiber Matting

• 2.4 Live Fascines

• 2.5 Brush Mattress

• 2.6 Live Stakes

• 2.7 Branch Layering

Stream Bank Stabilization

What Zone is Eroding?

2.1 Natural Fiber Rolls

Limitations: - Avoid Streams with Unstable Beds - Vegetation Establishment Required - Avoid Bedrock Streams - Minimize Channel Encroachment - Not used in Outer Bends

Appropriate Uses: - Toe Stabilization for Small Streams - Aesthetic Treatment Preferred - Toe Protection in Ponds and Lakes - Can be Stacked - Used in Combination with 2.3 Fiber Matting - Used Above Rigid Toe-Protection

2.2 Live Soil Lifts

Limitations: • Fill Slopes Steeper than 1.5:1 (H:V) • Requires Toe Protection • Establishment of Vegetation Critical

Appropriate Uses: • Rebuilding Stream Bank • Stream Bank Fill is poorly graded

sand • Internal Seepage and Sloughing is a

Concern • As component of Stream Bank

Protection

2.3 Natural Fiber Matting

Limitations: • Not for Large or Steep Fill sections • Biodegrades over time, vegetation is vital

component • High velocity and stress banks may require

Geosynthetic Slope Stabilization • Straw and Jute Matting Limited to outside

active channel • Should not be used where Livestock access

Stream

Appropriate Uses: • Stabilization on Graded Stream Banks • Graded Banks with Slopes of 2:1 or less • Upper Bank Treatment in combination with

Lower Bank Treatment • A Component of 2.2 Live Soil Lifts • Combined with 2.1 Fiber Rolls and 2.6 Live

Stakes

2.4 Live Fascines

Limitations: • Rocky Soils, Well Drained Slopes

and Shade limit Growth • Planted in Dormant Season • Avoid High Flow Areas • Stable Toe Slope Needed • Not for Over widened Channels

Appropriate Uses: • Create Breaks on Long Slopes (Parallel to

Stream Flow) • Combined with 1.5 Rock Toe Revetment,

2.1 Fiber Rolls, and 2.3 Fiber Matting • Toe Protection in Low Flow Streams • Used above Base Flow Elevation

2.5 Brush Mattress

Limitations: • Not for Over Widening Slopes • Requires Stable Toe • Watering may be needed • Installed in Dormant Season • Drains needed if Seepage is problem

Appropriate Uses: • Protect Slopes for Vegetative Cover • Total Vegetative Cover on Slope is

Desired • Slopes less than 2:1 (H:V) • Slope Length less than 10 feet

2.6 Live Stake

Limitations: • Need contact with Water Table • Planted Late Fall or Early Spring • Vegetation Growth Slower • Not for Shaded Areas • Wet Tolerant Species Preferred

Appropriate Uses: • Stabilize Graded or Eroding Stream Banks • Can be a Component of All Practices • Stand Alone Practice on Slopes of 4:1 (H:V) • Used Above Toe Protection

2.7 Branch Layering

Limitations: • 2.2 Soil Lifts used in Larger Areas • Requires Stable Toe • Vegetation Establishment Vital • Not for Shaded areas • Not Suited for Well Drained Soils

Appropriate Uses: • Repair of Slumps Less than 4 feet deep

and 5 feet wide • Repair of Gullies less than 1 foot deep

and 2 feet wide and 15 feet long

Grade Control Structures

• 3.1 Rock Cross Vanes

• 3.2 Rock W Weirs

• 3.3 Rock Vortex Weirs

• 3.4 Step Pools

• 3.5 Log Drops and V Log Drops

Head cuts and Cutoff Channels

3.1 Rock Cross Vane

Limitations: • Accurate Understanding of Channel Morphology • Sandy Streams requires filter fabric • Large Rock Difficult in small streams • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Grade Control of unstable stream bed • To Direct stream flow towards center of channel • Fish Habitat Enhancement • To Narrow a over widening channel

3.2 Rock W Weir

Limitations: • Accurate Understanding of Channel Morphology • Sandy Streams requires filter fabric • Large Rock and Shape difficult in small streams • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Protection of Bridge Piers • Channels with widths greater than 40 feet • Grade Control of unstable stream bed

3.3 Rock Vortex Weir

Limitations: • Difficult to construct Parabolic Shape • Litter and Debris may clog gaps • Accurate Understanding of Channel

Morphology • Sandy Streams requires filter fabric • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Useful in Small Streams where Cross Vane is needed • Grade Control of unstable stream bed • To Direct Stream Flow Towards the Channel Center • Fish Habitat Enhancement

3.4 Step Pool

Limitations: • Limited Design Guidance • Sandy Streams requires filter fabric • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Confined Channels with Slopes > 3% • Grade Control requiring drops > 6 inches • Connect two reaches with different elevation • Backwater a culvert to provide fish passage • Fish Habitat Enhancement

3.5 Log Drops

Limitations: • Flatter Streams < 0.5% • Biodegrade over time • Barriers to fish passage possible

Appropriate Uses: • Used in Small Streams where Step-Pool Required • Streams with Slopes > 3% • Where Woody Debris are natural grade controls • For Small Erosional Gully Repairs to Provide Grade

Control

Flow Deflection Structures

• 4.1 Rock Vane

• 4.2 J Hook Vane

• 4.3 Wing Deflectors

• 4.4 Log Vanes

• 4.5 Cut-Off Sills

When to Manage Channel Migration?

Obstructions?

4.1 Rock Vane

Limitations: • Channel Slopes greater than 3% • Accurate Understanding of Channel

Morphology • Sandy Streams requires filter fabric • Large Rock Difficult in small streams • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Deflect Erosional Forces from Stream Bank • Deflect stream at upstream end of

meander bend • Used in gravel streams • Fish Habitat Enhancement

4.2 J-Hook Vane

Limitations: • Spans more than half the Channel width • Problematic in Deep Channels • Accurate Understanding of Channel Morphology • Sandy Streams requires filter fabric • Large Rock Difficult in small streams • Heavy Equipment and Skilled Operator • Additional Foundation Design Needed

Appropriate Uses: • Deflect Erosional Forces from Stream Bank • Deflect stream at upstream end of meander bend • Used in gravel streams • Fish Habitat Enhancement

4.3 Wing Deflector

Limitations: • Large Sediment and Debris Loads • Not useful in Bedrock Channels with no

Scour Pool potential • Proper Analysis needed to prevent

adjacent stream bank erosion

Appropriate Uses: • Overly Wide Base Flow Channel • Increased Depth and flow velocity desired • Provides Meanders in Straight Gravel Channels • Channel Slopes < 3% • Stable Channels with no Defined Base Flow

Channel

4.4 Log Vane

Limitations: • Not used in Channel Slopes > 3% • Limited Lengths, may not be suitable in larger

streams • Degrades over time and may need replacement • Accurate Understanding of Channel Morphology

Appropriate Uses: • Deflect Erosional Forces from Stream Bank • Useful in sandy/ silty stream with a desire

for woody debris • Fish Habitat Enhancement

4.5 Cut-Off Sills

Limitations: • Ineffective in Bedrock Channels • Requires sediment load to

encourage deposition behind sills

Appropriate Uses: • Overly Wide Base Flow Channel • Straight or riffle sections of Gravel Channels • Channel Slopes < 3% • Stable Channels with no Defined Base Flow Channel • Linear Deflector defines edge of sill • Vegetative Sill used in sandy streams

Temporary Flow Diversion

• 5.1 Pump-Around Diversion

• 5.2 Sandbag/Stone Diversion

• 5.3 Diversion Pipe

• 5.4 Portable Dams/Barriers

• 5.5 Temporary Diversion Channel

5.1 Pump-Around Diversion

Limitations: • Stream Flow determines Pump Capacity

and Height of Barriers • Pumps can Break • Storm Surges

Appropriate Uses: • Where a Segment needs to be dewatered • Wateshed less than 1 square mile

5.2 Sandbag/Stone Diversion

Limitations: • Smaller Area of Stream access • May Fail during Storm Surges • Best for small channels

Appropriate Uses: • To construct or repair small localized areas

of stream bank and bed

5.3 Diversion Pipe

Limitations: • Can reduce equipment access and

maneuverability • Difficult to use with Grade Control

Structures • Difficult to Adjust Pipe after Installation

Appropriate Uses: • Where a Segment needs to be

dewatered • When Flow Required to divert is small • Watershed less than 1 square mile

5.4 Portable Dam/Barrier

Limitations: • Difficult to Adjust after Installation

Appropriate Uses: • Use in Larger Rivers with depths up to 7 ft • Alternative to 5.2 Stone or Sandbag • When conditions of dewatering

encourage use of alternative

5.5 Temporary Diversion Channel

Limitations: • Cannot be adjusted or moved • May reduce equipment access and

maneuverability • May not be practical in Large Channels

Appropriate Uses: • When entire stream channel needs to be

dewatered • When Stream Flow diverted cannot be done

with a pump or pipe • When adequate floodplain width is available

Riparian Forested Buffer

• Is a natural Filter located between upland landscape and waterways.

• Is an area of land that is maintained to protect stream banks and improves water quality

• This Best Management Practice (BMP) is cornerstone for long term protection of the Chesapeake Bay and Forest is the natural cover for most streams in this region.

Riparian Management

• Zone 1: Protection Zone – The area adjacent to the stream bank or edge of water – No Disturbance zone with minimum maintenance to control invasive

species and remove snags

• Zone 2: Management Zone – The transition area from open turf or pavement to forest – Minor Maintenance to control invasive species and permit passive

recreation

• Zone 3: Erosion Control Zone – The area of managed turf adjacent to the forested buffer – Higher Maintenance to maintain uniform, mature turf that can inhibit

erosion

Riparian Management

Forested Buffer Benefits

• Stabilize and Protect the Stream Bank from Channel Erosion

• Protects the Floodplain by preventing cutoff channels • Reduce Sediment Loads from surface runoff and flood

flows • Capture and Filter Surface Runoff • Intercept and Process Air Pollutants • Provides Shade and Regulates Stream Temperatures • Provides Wildlife and Aquatic Habitat

Costs

Cost for a 500 linear foot Project *Does not include additional Labor Costs for Plantings