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Greg Jennings, PhD, PE

Professor, Biological & Agricultural Engineering

North Carolina State University

[email protected]

Jason Zink, PE

Zan Price, PE

Mike Shaffer, PE

Dave Penrose

Barbara Doll, PE

Kris Bass, PE

Karen Hall

Mitch Woodward

Stream Assessment

mailto:[email protected]

… 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?

Hydrologic (Water) Cycle: describes the

flow of water on the planet in response

to solar energy and gravity

Stream Corridor Restoration: Principles, Processes, and Practices.

1998. Federal Interagency Stream Restoration Working Group.

Water Cycle Components:

Precipitation

Runoff

Infiltration

Evapotranspiration

Groundwater flow

Average annual precipitation is highly variable and the timing of

rainfall each year is unpredictable

Extreme Weather!

Watershed:

“Area of land that drains water, sediment, and

dissolved materials to a common outlet at some

point along a stream channel”Dunne and Leopold, 1978

Watershed form is influenced by:

1. Climate

2. Geology & Soils

3. Fluvial Geomorphology

4. Vegetation

5. Land Uses

Watersheds include many

land uses affecting flow and

water quality

From Webster's Revised Unabridged Dictionary (1913) :

Watershed, n [Cf. G. wasserscheide; wasser water + scheide a place where two things separate, fr. scheiden to separate.]

1. The whole region or extent of country which contributes to the supply of a river or lake.

2. The line of division between two adjacent rivers or lakes with respect to the flow of water by natural channels into them; the natural boundary of a basin.

Other Terms: Catchment, Drainage basin, River basin

North Carolina River Basins

River basins include watersheds of varying sizes and shapes, each with a network of streams delivering water to an outlet

Watershed Stream Network

Neuse River Basin, NC

Watershed Functions:

Transport & Storage:

1. Water

2. Sediment

3. Dissolved Materials

Habitat:

1. Animals

2. Plants

3. Humans

Water Transport to StreamsRainfall moves across the land as runoff or through the ground

toward streams to provide baseflow



Losing Stream Gaining StreamGroundwater Recharge Groundwater Discharge

Groundwater Influences Streamflow



Streamflow Duration and Frequency:Classification based on connection to groundwater

Intermittent(sometimes losing)

Perennial(gaining stream)

Ephemeral(losing stream)

Strahler Stream Order:Classification system describing position within the drainage network

Stream Corridor Restoration: Principles, Processes, and Practices. 1998.

Federal Interagency Stream Restoration Working Group.

First order

streams may

be

ephemeral, inte

rmittent, or

perennial in

relation to

groundwater

connection

Stream Functions

1. Transport water

2. Transport sediment

3. Habitat (aquatic & terrestrial)

4. Recreation

5. Aesthetics

6. Safe Water Supply

Water Transport & Storage

Hydrology: The study of the flow of the earth’s waters through

the hydrologic cycle

Hydrograph: Displays change in flow (discharge, Q, over time)

www.Geology.com

Mean Daily Flow

Falling

Limb

Rising

Limb

Peak Flow

Hydrologic Responses to

Urbanization

1. Increased discharge

2. Increased peak discharge

3. Increased velocities

4. Shorter time to peak flow

5. More frequent bankfull events

6. Increased flooding

7. Lower baseflow

8. Less ground water recharge

Hydrograph Changes Due to Urbanization

Increased impervious surface results in more runoff and higher peak flow

Rural

Urban

0 10 20 30 40 50 60 70 80

% Impervious

Urban

Drainage

Network

Stream Condition Related to Impervious Surface

Water quality and stream health decline in relation to impervious surface percentage

Good

Fair

Poor

Impaired

Protected

Degraded

Source: Center for Watershed Protection

Channel incision and bank erosion increase due to channelization

and increased stormwater runoff

Urban streams have special challenges due to urban

infrastructure (storm sewer and sanitary sewer)

In addition to stormwater and sewer systems, urban streams are

also challenged by confinement

Fluvial Geomorphology:

study of landforms and the fluvial processes

that shape them

Fluvial Processes:

associated with flowing water, including sediment

erosion, transport, and deposition

• Channel (bed & banks)

• Floodplain

• Water

• Sediment

• Plants & animals

Stream: A system of

fluvial forms & habitats

Photo Credit: Eve Brantley, Auburn University

Fluvial Forms• Bar

• Channel

• Confluence

• Cutoff channel

• Delta

• Floodplain

• Gorge

• Gully

• Meander

• Oxbow lake

• Pool

• Riffle

• Stream

• Valley

• Waterfall

• Watershed

Fluvial Processes and Landforms

1. How do stream systems work?

2. What determines stream size & shape

(i.e. morphology)?

• Communities of organisms and their physical,

chemical, and biological environments

Streams are ecosystems

Courtesy of Francois Birgand, NCSU

Stream Ecosystems

• Mostly downstream

fluxes of energy

and matter

• Lateral and vertical

connections to the

riparian and

hyporheic zones

Courtesy of Francois Birgand, NCSU

River Continuum

Concept

Connections

• Watershed to

Corridor to Stream

• Biological

communities

upstream and

downstream



Hyporheic Zone

Field Investigations

What is living in the

stream?

What are the physical and

chemical conditions of the

stream?

Provisioning – food, energy, industry

Regulating – climate, waste, nutrients

Supporting – water quality, pest control

Cultural – recreation, inspiration

Preserving – species diversity

Ecosystem Services

Self-Design

The reorganization, substitution and shifting of an

ecosystem (dynamics and functional processes)

whereby it adapts to the environment superimposed

upon it. (Mitsch & Jorgensen, Ecological Engineering)

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

What makes a stream healthy?

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

1. Bed Stability & Diversity – Problems

• 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

2. Sediment Transport Balance

• Excess stream power – eroding bed

• Insufficient stream power – aggradation

PoolRoots Wood

Leaf Pack

RiffleRocks

3. In-stream Habitat & Flow Diversity

Plants

Overhanging Bank

Stream Habitats

Macrohabitats: riffles,

runs, pools, glides,

steps, side channels

Microhabitats: roots,

leaf packs, wood,

rocks, plants,

hyporheic zone

Food Web

Diversity of habitats

What habitats do you see?

Pool

Roots

Wood

Leaf Pack

Riffle

Rocks

3. In-stream Habitat – Problems

• 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

4. Bank Stability – Problems

• Loss of vegetation

• High, steep banks – channelization

5. Riparian Buffer (Streamside Forest)

• Diverse native plants

• Food and shade

5. Riparian Buffer – Problems

• 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

6. Active Floodplain – Problems

• Channel incision

• Floodplain fill and encroachment

7. Healthy Watershed

• Stormwater management

• Wastewater management

• Upstream sediment control

7. Healthy Watershed – Problems

• Stormwater energy and volume

• Point and nonpoint source pollution

• Erosion and sediment

Stream Impairments

• Straightening & dredging

• Floodplain filling

• Watershed manipulation

• Sedimentation & stormwater

• Pollution discharges

• Utilities & culverts

• Buffer removal

• Disdain & neglect

Stream Impairment

Causes (US EPA)

1. Pathogens

2. Sediment

3. Nutrients

4. Organic Enrichment

5. Habitat Alterations

6. PCBs

7. Metals

8. Flow Alterations

9. Temperature

10. Mercury

Why Restoration?

• Water quality impairments

• Habitat loss

• Ecosystem degradation

• Land loss

• Safety concerns

• Infrastructure damage

• Flooding

• Aesthetics

1. Watershed management

2. Floodplain reconnection

3. Channel morphology –

dimension, pattern, profile

4. Sediment transport balance

5. Habitat enhancements

6. Bank stabilization

7. Riparian buffer – native

plants

Restoring Stream Health

Stream Functions

1. Transport water

2. Transport sediment

3. Habitat (aquatic & terrestrial)

4. Recreation & aesthetics

5. Safe Water Supply

Q = V A = Discharge (cfs)

V = Velocity (ft/s)

A = Cross-Section Area (ft2)

V related to slope, channel shape, and channel

roughness

Velocity &

Discharge

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

Manning Formula

A = 40 sq ft

W = 22 ft

R = 1.7 ft

S = 0.010 ft/ft

n = 0.040

V = 5.0 ft/s

Q = 200 cfs

A = 220 sq ft

W = 55 ft

R = 3.5 ft

S = 0.004 ft/ft

n = 0.035

V = 6.1 ft/s

Q = 1350 cfs

R = 1.5 ft

S = 0.0012 ft/ft

n = 0.038

V = 1.8 ft/s

Q = 89 cfs

= 0.11 lb/sq ft

Competence = ~30 mm

Stream Corridor Longitudinal Profile



Sediment Transport

Flowing water does work:

• Erosion

• Transportation

• Deposition (of alluvium)

http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html

Erosion: Detachment of material from bed and banks

95% of stream energy used to overcome friction

Remaining energy used for Erosion Processes:

• Flowing water dissolves materials

• Hydraulic action dislodges materials

• Abrasion of heavy materials rolling on bottom

http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/

fluvial_systems/geologic_work_of_streams.html

Transportation: Movement of material by water

Stream Load includes:

dissolved + suspended + bed load

Capacity: maximum load that can be

transported for a given discharge

(increases with velocity and turbulence)

Competence: largest size material that

can be transported for a given discharge



Bedload is related to Discharge for Each River

Deposition:

Aggradation: Raising the bed elevation

Bars: Depositional areas that may change flow directions



Bed Material (Substrate)

Silt/Clay: < 0.062 mm

Sand: 0.062 – 2 mm

Gravel: 2 – 64 mm

Cobble: 64 – 256 mm

Boulder: 256 – 2048 mm

Substrate

Characterization

Wolman Pebble Count


High Slope Moderate Slope Low Slope

Velocity & Particle Size Determine Process

http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html

V = 5 ft/s

V = 1 ft/s

Shear Stress: fluid force per unit area

acting on the streambed

= Rs = Shear Stress (lb/ft2)

= Unit Weight of Water = 62.4 lb/ft3

R = Hydraulic Radius (ft) = A / P

S = Average Water Surface Slope (ft/ft)

A = Riffle Cross-Section Area (ft2)

P = Wetted Perimeter (ft)

P = Wbkf +2*Dbkf (approx)

Stream Competence (www.epa.gov/WARSSS)

A = 40 sq ft

W = 22 ft

R = 1.7 ft

S = 0.010 ft/ft

= 1.0 lb/sq ft

Competence = ~250 mm

A = 220 sq ft

W = 55 ft

R = 3.5 ft

S = 0.004 ft/ft

= 0.8 lb/sq ft

Competence = ~200 mm

Sediment

Deposition:

• Point bar

• Lateral bar

• Mid-channel bar

• Transverse bar

• Delta bar

Point Bars:

Inside meander

bends

Lateral Bars:

Formed in

straight channels

Mid-channel Bars:

Formed in over-

wide channels

Transverse Bars:

Formed in straight

channels

Meandering Stream: Alluvial Forms

Point Bar

ScarpBankfull Stage

Thalweg

Flow DownstreamFloodplain

Riffle

Pool

Right

Bank

Left Bank

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)


Bankfull

Channel

Evolution

(Succession)

Response to

incising forces

Stream Corridor Restoration:

Principles, Processes, and Practices.

1998. Federal Interagency Stream

Restoration Working Group.

Bankfull

Terrace

Incised System: Floodplain Creation

Floodplain

Terrace

Stream Morphology:

size and shape of channel & floodplain

(dimension, pattern, profile)

Colluvium is loose sediment

transported by gravity and

deposited at the bottom of a

slope.

Alluvium is sediment deposited

by a river in the channel or

floodplain

Alluvial valleys occur where

sediment particles are dropped

by slow-moving water.

Valley type affects

stream morphology

Valley Types: (www.epa.gov/watertrain/stream_class)

Valley Type II

Moderately steep, gentle sloping side

slopes often in colluvial valleys

From EPA Watershed Academy: Fundamentals of the Rosgen Stream Classification System

Valley Types: (www.epa.gov/watertrain/stream_class)

Valley Type VIII

Wide, gentle valley slope with well-developed

floodplain adjacent to river terraces

From EPA Watershed Academy: Fundamentals of the Rosgen Stream Classification System

Stream Corridor Lateral Profile


Floodplains: Critical Stream Components

Floodplain Functions

• Floodwater storage

• Reducing peak flows

• Erosion prevention

• Water quality

• Groundwater recharge

• Food & shade

• Habitats

Floodplain

Left BankRight Bank

Downstream

Terrace

Streambed

Thalweg

FloodplainLeft Bank Right

Bank

Downstream

Terrace

Streambed

Thalweg

Pool Cross-Section (Meandering Stream)


Natural Stream Channel Stability

(from Leopold)

• River has a stable dimension, pattern and profile

• Maintains channel features (riffles, pools, steps)

• Does not aggrade (fills) or degrade (erodes)

Dimension (cross-section)

• Area

• Width

• Depth

• Width/Depth Ratio

• Entrenchment Ratio

• Bank Height Ratio

Bankfull Stage: “incipient flooding”“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 & Leopold,1978)


Bankfull

Terrace

Dimension: Cross-Section

Riffle Dimensions

Bankfull

Wbkf

Abkf

Measure Bankfull Width (Wbkf) and Bankfull Area (Abkf)

Mean Depth, dbkf = Abkf / Wbkf

Width to Depth Ratio, W/d = Wbkf / dbkf

dbkf

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

Bankfull Width, Wbkf = 36 ft; Bankfull Area, Abkf = 112 ft2

Mean Depth, dbkf = Abkf / Wbkf = 112 / 36 = 3.1 ft

Width to Depth Ratio, W/d = Wbkf / dbkf = 36 / 3.1 = 11.5

Entrenchment Ratio

ER = Wfpa / Wbkf

Bankfull

2 x dmbkf

above thalweg

Wfpa

Wbkf

dmbkf

Wfpa = Width of Flood Prone Area measured at the

elevation twice bankfull max depth above thalweg

Wbkf = Width of Bankfull Channel

ER = Wfpa / Wbkf = 75 / 15 = 5.0

Flood water flows onto floodplain

several times each year

Rocky Branch Phase II Reach 2:

Priority 2 (floodplain excavation, C channel)

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

Rocky Branch Phase II Reach 1:

Priority 3 (floodplain excavation, Bc channel)

Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2

Bank Height Ratio

BHR = LBH / dmbkf

BankfullLBH

dmbkf = Max Depth from bankfull stage to thalweg

dmbkf

LBH = Low Bank Height (Max Depth to thalweg)

BHR = 5.3 / 2.5 = 2.1

1

10

100

1000

10000

0.1 1 10 100

Ba

nk

full

D

isch

arg

e,

Q (

cfs

)

Drainage Area (sq mi)

Hydraulic Geometry Regional Curves

NC Piedmont

NC Mtn

MD Alleghany

MD

NY

VT

OH 01

OH 05

OK

SW OR

Pacific NW

AZ

AZ & NM

1

10

100

1000

0.1 1 10 100

Cro

ss-s

ect

ion

Are

a (

sq f

t)

Drainage Area (sq mi)

Hydraulic Geometry Regional Curves

NC Piedmont

NC Mtn

MD Alleghany

MD

NY

VT

OH 01

OH 05

OK

SW OR

Pacific NW

AZ

AZ & NM

Alluvial (low-gradient) streams

naturally meander across a

valley with a somewhat

predictable pattern

Pattern (plan form)

Pool

Run

Point Bar

(deposition)

Glide

Riffle

Meandering Stream: Alluvial Forms

Oxbow

Formation in

Meandering

Streams


Principles, Processes, and Practices. 1998.

Federal Interagency Stream Restoration Working

Group.

Chute cutoff across tight meander bend

Oxbows

Sinuosity = stream length / valley length

K = 1850 / 980 = 1.9

Valley Length

Plan Form Relationships

Meander Length Ratio = meander length / width = 78/15 = 5.2

Meander Width Ratio = belt width / width = 57/15 = 3.8

Radius of Curvature Ratio = radius / width = 23/15 = 1.5

Meander

Length

Belt

Width

Glide Slope

Riffle Slope

Run Slope

Pool Slope

Water Surface

Thalweg

Pool Spacing, Lp-p

Profile (bedform)

Riffle Slope Ratio, Srif / Sav

Pool Slope Ratio, Spool / Sav

Pool-to-Pool Spacing Ratio, Lp-p / Wbkf

Stream Bedform Variability:

Slope Substrate size

Velocity Oxygenation

Shear stress Habitats

Riffles

• Steep slope

• High velocity

• High shear stress

• Large substrate

• High porosity

Importance of Riffles

• Areas of oxygenation

• Highly diverse substrate and habitat

• Diverse macroinvertebrate population

Pools

• Flat slope

• Low velocity

• Low shear stress

• Small substrate

• Scour during high flow

Importance of Pools

• Refuge for fish during

low flow, drought

periods

• Rest stop and food

area for fish

• Predator refuge for

young fish

River Dimensions

Velocities:

Low flow and

Flood flow

Little Garvin

Creek, Clemson, SC

Channel dimensions in a meandering stream

www.uwsp.edu/gEo/faculty/lemke/geomorphology/lecture_outlines/04_fluvial_landforms.html

Profile is related to Pattern

Step Pool Streams

(high gradient)


Grade Controls

Nickpoints

Flow diversity

improves habitat:

• Riffles

• Steps

• Pools

Natural Stream Channel Stability

(from Leopold)

• River has a stable dimension, pattern and profile

• Maintains channel features (riffles, pools, steps)

• Does not aggrade (fills) or degrade (erodes)

Equilibrium Controlling Variables

• Width

• Depth

• Slope

• Velocity

• Discharge

• Flow resistance

• Sediment size

• Sediment load

Leopold et al (1964)

Channel Forming

Discharges

and Regional

Curves

Channel-forming (dominant) discharge

Estimated using:

• Effective discharge

• Bankfull discharge

• Discharge associated with

recurrence interval

(typically 1 to 2 year)

Effective Discharge

Transports the

most sediment

over a long time

Bankfull Discharge

Return Period typically 1 to 2 years

Flow fills active channel and spreads onto floodplain

Represents break between channel & floodplain processes

For channel in equilibrium, assumed to equal the effective discharge

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)


Bankfull

Bankfull Indicators

• Top of streambank (floodplain)

• Break in slope on streambank

• Top of point bar

Bankfull

Bankfull

Bankfull

Channel

Evolution

(Succession)

Response to

incising forces


Principles, Processes, and Practices.

1998. Federal Interagency Stream

Restoration Working Group.

Bankfull

Terrace

Bankfull

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