Greg Jennings, PhD, PEProfessor, Biological & Agricultural EngineeringNorth Carolina State Universityjennings@ncsu.edu

Understanding and Restoring Streams

… a body of water with a current, confined within a bed and streambanks

Synonyms:  bayou, beck, branch, brook, burn, creek, crick, kill, lick, rill, river, rivulet, run, slough, syke

A stream is:• conduit in the water cycle• critical habitat• connected to a watershed

What is a Stream?

Fluvial Geomorphology:The study of landforms and fluvial processes

Fluvial processes are associated with flowing water, including sediment erosion, transport, deposition

Fluvial Forms• Bar• Channel• Confluence• Cutoff channel• Delta• Floodplain• Gorge• Gully• Meander• Oxbow lake• Pool• Riffle• Stream• Valley• Waterfall• Watershed

PoolRun

Point Bar (deposition)

Glide

Riffle

Meandering Stream: Alluvial Forms

Bankfull

Bankfull Stage“corresponds to the discharge at which channel maintenance is the most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work results in the average morphologic characteristics” (Dunne and Leopold,1978)

Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.

• Channel (bed & banks)• Floodplain• Water & Sediment• Plants & Animals

Stream Ecosystems

Photo Credit: Eve Brantley, Auburn University

Stream Functions & Services1. Transport water

2. Transport sediment

3. Habitat (aquatic & terrestrial)

4. Recreation & aesthetics

5. Safe Water Supply

Effects of Urbanization on Streams (US EPA)

Urban Stream Syndrome (USS)• Response to watershed changes

• Loss of natural functions & values

• Causes problems locally & downstream

• Requires systematic assessment & treatment

Symptoms of USS

• Erosion & incision• Water quality decline• Habitat loss• Ecosystem degradation• Flooding• Land loss• Infrastructure damage• Recreation impaired• Aesthetics impaired• Economic loss

Urban Stream: Incision & bank erosion

Causes of USS• Watershed impervious• Channelization• Impoundments• Diversions• Floodplain filling• Pollution discharges• Sedimentation• Stormwater runoff• Utilities & culverts• Buffer loss• Neglect & Ignorance

University of Central Florida

Urban Disturbances to Hydrologic Cycle

Hydrograph Changes Due to Urbanization

0 20 40 60 800

10

20

30

40

50

Time (hours)

Stre

am F

low,

Q (

cfs)

Rural

UrbanHigher Peak FlowMore Runoff VolumeFlashier ResponseLower Baseflow

Runoff: more

Infiltration: less

Flooding: more

Baseflow: less

Constraints: Utilities, Road, Bridges, Culverts

What Makes a Stream Healthy?1. Bed stability & diversity

2. Sediment transport balance

3. In-stream habitat & flow diversity

4. Bank stability (native plant roots)

5. Riparian buffer (streamside forest)

6. Active floodplain

7. Healthy watershed

1. Bed Stability & Diversity• Appropriate size sediments to

resist shear stress

• Riffle/Pool sequences in alluvial streams

• Step/Pool sequences in high-gradient streams

Photo Credit: Eve Brantley, Auburn University

Riffles• Steep slope• High velocity & shear stress• Large substrate• High porosity & groundwater

exchange

Pools• Flat slope• Low velocity & shear stress• Small substrate• Scour during high flow

Problems: Bed Stability & Diversity• Headcut and excess scour

• Plane bed – filling of pools

• Armoring

2. Sediment Transport Balance• Minor erosion & deposition

• Alluvial bars and benches

• Sufficient stream power to avoid aggradation

Problems: Sediment Transport Balance• Excess stream power – eroding bed

• Insufficient stream power – aggradation

Streams convey water and sediment

Channel Evolution Model (Schumm, 1984)

Lane’s Balance (Lane, 1955)

Macrohabitats: riffles, runs, pools, glides, steps, side channels, scour holes

Microhabitats: roots, leaf packs, wood, rocks, plants, hyporheic zone

3. In-stream Habitat & Flow Diversity

Problems: In-stream Habitats• Uniform flow – lack of diversity

• Lack of wood, leaves, roots

• Water quality – DO, nutrients, toxics

4. Bank Stability• Dense native

plant roots

• Low banks with low stress

Problems: Bank Stability• Loss of vegetation

• High, steep banks – channelization

5. Riparian Buffer (Streamside Forest)• Diverse native plants

• Food and shade

Problems: Riparian Buffer• Mowers and moo’ers

• Invasive plants

• Armoring and impervious surfaces

6. Active Floodplain• Regular (every year) flooding to relieve stress

• Riparian wetlands

• Stormwater retention & treatment

Problems: Active Floodplain• Channel incision

• Floodplain fill and encroachment

7. Healthy Watershed• Stormwater management

• Wastewater management

• Upstream sediment control

Problems: Healthy Watershed• Stormwater energy and volume

• Point and nonpoint source pollution

• Erosion and sediment

Ecosystem Restoration:

“activities that initiate or accelerate the recovery of ecosystem health, integrity, and sustainability”(SER, 2004)

Planning a Stream Project:

• Goals? Stability, Habitat, Recreation?• Constraints? Access, Land Availability, Utilities?• Feasibility? Will it Work?• Constructability? Equipment, Materials, Time/$?

Case Study: Long Creek (1995-2005)• Dairy Farm: Fencing, Bank Stabilization, Planting

10 years later

Roaring River, Stone Mt State Park (2000-10)• Trout Stream: Channel Realignment, Structures, Planting

10 years later

Rocky Branch, NCSU Campus• Urban Stream: Channel Realignment, Structures, Planting

1. Channel morphology

2. Floodplain structure

3. Hydrologic & hydraulic analysis

4. In-stream structures

5. Habitats & vegetation

6. Site & watershed conditions

7. Monitoring, maintenance, education

Restoration Components

1. Channel Morphology• Dimension (baseflow, bankfull, flood flows)

• Pattern (meandering, straight, braided)

• Profile (bedform – riffle, run, pool, glide, step)

2005 South Fork Mitchell River 2006

Photo Credits: Darrell Westmoreland, North State Environmental, Inc.

2011 South Fork Mitchell River

2011 South Fork Mitchell River

High-quality “reference” streams serve as design templates

Wbkf

dbkfAbkf

Bankfull Width, Wbkf = 9.3 ft; Bankfull Area, Abkf = 13.9 ft2

Mean Depth, dbkf = Abkf / Wbkf = 13.9 / 9.3 = 1.5 ft

Width to Depth Ratio, W/d = Wbkf / dbkf = 9.3 / 1.5 = 6.2

Morphologic Stream Classification Systems• Schumm (1977)

– Alluvial channels– Meandering, straight, braided– Type related to channel stability & sediment transport

• Montgomery & Buffington (1993)– Alluvial, colluvial, bedrock channels– Channel response related to sediment inputs– 6 classes of alluvial channels: cascade, step-pool,

plane-bed, riffle-pool, regime, and braided• Rosgen (1994)

www.wildlandhydrology.com

Rosgen Classification of Natural Rivers• Based on physical

characteristics (empirical)• Requires field

measurements• Requires bankfull

dimensions

www.wildlandhydrology.com

www.wildlandhydrology.com

G4 Eastern NC

2003

2000

2003

2001

2. Floodplain Structure• Regular (every year) flooding to relieve stress

• Floodwater retention & riparian wetlands

• Stormwater discharge retention & treatment

Entrenchment RatioER = Wfpa / Wbkf

Bankfull2 x dmbkf

above thalweg

Wfpa

Wbkf

dmbkf

Wfpa = Width of Flood Prone Area measured at the elevation twice bankfull max depth above thalwegWbkf = Width of Bankfull Channel

2006 Town Creek Tributary 2007

Priority 1: Raise channel to existing valley and construct new meandering channel

Rain will come during and immediately following construction!

ER = 15; W/d = 12

2008 Town Creek Tributary

Priority 1:lift channel

Incised Stream

Priority 2 & 3:lower floodplain

Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.

Priority 2: Excavate lower floodplain and construct new meandering channel

2008 White Slough 2010

ER = 6; W/d = 11

White Slough 2010

Wfpa

Wbkf

Entrenchment Ratio = Wfpa / Wbkf = 90/15 = 6

Priority 2: Excavate lower floodplain and construct new meandering channel

2004 NCSU Rocky Branch 2005

Flood water flows onto floodplain several times each year

Wfpa

Wbkf

Rocky Branch Phase II Reach 2:Priority 2 (floodplain excavation, C channel)

Entrenchment Ratio = Wfpa / Wbkf = 90/20 = 4.5

2005 NCSU Rocky Branch 2006

Priority 3: Excavate narrow floodplain benches in confined systems

ER = 2.2; W/d = 12

Wfpa

Wbkf

Rocky Branch Phase II Reach 1:Priority 3 (floodplain excavation, Bc channel)Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2

2008 NCSU Rocky Branch

Priority 3: Excavate narrow floodplain benches in confined systems

2009 Little Shades Creek 2010

ER = 1.6; W/d = 15

Wfpa

Wbkf

Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6

Little Shades Creek 2010

In-Stream Structures (Logs & Rocks)• Streambank protection• Habitat enhancement (pools, aeration, cover)• Grade control• Sediment transport

Structure Criteria:• Natural materials• Habitats & passage for aquatic organisms• Natural sediment transport (alluvial systems)

Do you like these?

Boulder J-Hook Vane

Runaway Truck Ramp

Boulder J-Hook Vane• 3-5 % arm slopes

• 20-25 degree arm angles

• Boulder footers & non-woven geotextile

• 0.5 ft drops over j-hook inverts

Boulder Vane20-25 degree angles

3-5 % arm slopes

20-25 degrees

3-5 % arm slopes

Boulder

J-Hook Vane

Log Vane• 2-4 % arm slopes

• 20 degree arm angles

• Sealed with woven geotextile & backer logs

Log J-Hook Vane• Direct flow away from bank around bend• Grade control and scour pool• Brush toe buried under log vane• Backer logs & geotextile

Log J-Hook Vane• Hook boulders control grade• Footer boulders and geotextile• Boulder sills

Log J-Hook Vane• Hook boulders control grade• Footer boulders and geotextile• Boulder sills

Log J-Hook Vane

Multiple Log Vanes

Saugahatchee Creek

2007

2008

Multiple Log Vanes

Saugahatchee Creek

2009 January

2009 JulyPhoto Credit: Dan Ballard, Town of Auburn

Multiple Log Vanes: Saugahatchee Creek

2012 April Photo Credit: Dan Ballard, Town of Auburn

Boulder Cross Vane

Cross Vane• Direct flow in new channel alignment• Grade control and scour pool• Footer boulders & geotextile

• Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood

• Cut thalweg 0.5 ft deep

Cross Vane (logs embedded)

Double-Drop Boulder Cross Vane

Photo Credit: Darrell Westmoreland, North State Environmental, Inc.

Double-Drop Boulder Cross Vane

Offset Boulder Cross Vane at a Bridge

Boulder W-Vane

Boulder Double Wing Deflector

Constructed Riffle

1st Order Streambed Transplant• Substrate transfer from old channel to new channel

Constructed Riffle• Undercut bed 2 ft and backfill with gravel, cobble,

boulders, wood• Cut thalweg 0.5 ft deep

• Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood

• Cut thalweg 0.5 ft deep

Constructed Riffle

Riffles with Bouder/Log Steps

Wood• Food sources• Cover• Scour pools• Flow diversity

Brush Toe• Layers of logs and brush under water in pools• Live cuttings above water (silky dogwood, elderberry)• Matting, seed, transplanted alders on top

Brush Toe• Layers of logs and brush under water in pools• Live cuttings above water (silky dogwood, elderberry)• Matting, seed, transplanted alders on top

1. Plan for floods -- immediately & often

2. Plan for dry weather

3. Plan for vegetation maintenance

4. Understand constraints

5. Expect the Unexpected

Summary: Plan for Success