Page 1
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
Page 2
… 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?
Page 3
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.
Page 4
Water Cycle Components:
Precipitation
Runoff
Infiltration
Evapotranspiration
Groundwater flow
Page 5
Average annual precipitation is highly variable and the timing of
rainfall each year is unpredictable
Page 7
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
Page 8
Watersheds include many
land uses affecting flow and
water quality
Page 9
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
Page 10
North Carolina River Basins
River basins include watersheds of varying sizes and shapes, each with a network of streams delivering water to an outlet
Page 11
Watershed Stream Network
Neuse River Basin, NC
Page 12
Watershed Functions:
Transport & Storage:
1. Water
2. Sediment
3. Dissolved Materials
Habitat:
1. Animals
2. Plants
3. Humans
Page 13
Water Transport to StreamsRainfall moves across the land as runoff or through the ground
toward streams to provide baseflow
Stream Corridor Restoration: Principles, Processes, and Practices.
1998. Federal Interagency Stream Restoration Working Group.
Page 14
Losing Stream Gaining StreamGroundwater Recharge Groundwater Discharge
Groundwater Influences Streamflow
Stream Corridor Restoration: Principles, Processes, and Practices.
1998. Federal Interagency Stream Restoration Working Group.
Page 15
Streamflow Duration and Frequency:Classification based on connection to groundwater
Intermittent(sometimes losing)
Perennial(gaining stream)
Ephemeral(losing stream)
Page 17
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
Page 18
Stream Functions
1. Transport water
2. Transport sediment
3. Habitat (aquatic & terrestrial)
4. Recreation
5. Aesthetics
6. Safe Water Supply
Page 19
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
Page 20
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
Page 21
Hydrograph Changes Due to Urbanization
Increased impervious surface results in more runoff and higher peak flow
Rural
Urban
Page 22
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
Page 23
Channel incision and bank erosion increase due to channelization
and increased stormwater runoff
Page 24
Urban streams have special challenges due to urban
infrastructure (storm sewer and sanitary sewer)
Page 25
In addition to stormwater and sewer systems, urban streams are
also challenged by confinement
Page 26
Fluvial Geomorphology:
study of landforms and the fluvial processes
that shape them
Page 27
Fluvial Processes:
associated with flowing water, including sediment
erosion, transport, and deposition
Page 28
• Channel (bed & banks)
• Floodplain
• Water
• Sediment
• Plants & animals
Stream: A system of
fluvial forms & habitats
Photo Credit: Eve Brantley, Auburn University
Page 29
Fluvial Forms• Bar
• Channel
• Confluence
• Cutoff channel
• Delta
• Floodplain
• Gorge
• Gully
• Meander
• Oxbow lake
• Pool
• Riffle
• Stream
• Valley
• Waterfall
• Watershed
Page 30
Fluvial Processes and Landforms
1. How do stream systems work?
2. What determines stream size & shape
(i.e. morphology)?
Page 31
• Communities of organisms and their physical,
chemical, and biological environments
Streams are ecosystems
Courtesy of Francois Birgand, NCSU
Page 32
Stream Ecosystems
• Mostly downstream
fluxes of energy
and matter
• Lateral and vertical
connections to the
riparian and
hyporheic zones
Courtesy of Francois Birgand, NCSU
Page 33
River Continuum
Concept
Connections
• Watershed to
Corridor to Stream
• Biological
communities
upstream and
downstream
Stream Corridor Restoration: Principles, Processes, and Practices.
1998. Federal Interagency Stream Restoration Working Group.
Page 35
Field Investigations
What is living in the
stream?
What are the physical and
chemical conditions of the
stream?
Page 36
Provisioning – food, energy, industry
Regulating – climate, waste, nutrients
Supporting – water quality, pest control
Cultural – recreation, inspiration
Preserving – species diversity
Ecosystem Services
Page 37
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)
Page 38
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?
Page 39
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
Page 40
1. Bed Stability & Diversity – Problems
• Headcut and excess scour
• Plane bed – filling of pools
• Armoring
Page 41
2. Sediment Transport Balance
• Minor erosion & deposition
• Alluvial bars and benches
• Sufficient stream power to avoid aggradation
Page 42
2. Sediment Transport Balance
• Excess stream power – eroding bed
• Insufficient stream power – aggradation
Page 43
PoolRoots Wood
Leaf Pack
RiffleRocks
3. In-stream Habitat & Flow Diversity
Plants
Overhanging Bank
Page 44
Stream Habitats
Macrohabitats: riffles,
runs, pools, glides,
steps, side channels
Microhabitats: roots,
leaf packs, wood,
rocks, plants,
hyporheic zone
Page 46
Diversity of habitats
Page 47
What habitats do you see?
Pool
Roots
Wood
Leaf Pack
Riffle
Rocks
Page 48
3. In-stream Habitat – Problems
• Uniform flow – lack of diversity
• Lack of wood, leaves, roots
• Water quality – DO, nutrients, toxics
Page 49
4. Bank Stability
• Dense native
plant roots
• Low banks with
low stress
Page 50
4. Bank Stability – Problems
• Loss of vegetation
• High, steep banks – channelization
Page 51
5. Riparian Buffer (Streamside Forest)
• Diverse native plants
• Food and shade
Page 52
5. Riparian Buffer – Problems
• Mowers and moo’ers
• Invasive plants
• Armoring and impervious surfaces
Page 53
6. Active Floodplain
• Regular (every year) flooding to relieve stress
• Riparian wetlands
• Stormwater retention & treatment
Page 54
6. Active Floodplain – Problems
• Channel incision
• Floodplain fill and encroachment
Page 55
7. Healthy Watershed
• Stormwater management
• Wastewater management
• Upstream sediment control
Page 56
7. Healthy Watershed – Problems
• Stormwater energy and volume
• Point and nonpoint source pollution
• Erosion and sediment
Page 57
Stream Impairments
• Straightening & dredging
• Floodplain filling
• Watershed manipulation
• Sedimentation & stormwater
• Pollution discharges
• Utilities & culverts
• Buffer removal
• Disdain & neglect
Page 58
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
Page 59
Why Restoration?
• Water quality impairments
• Habitat loss
• Ecosystem degradation
• Land loss
• Safety concerns
• Infrastructure damage
• Flooding
• Aesthetics
Page 60
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
Page 61
Stream Functions
1. Transport water
2. Transport sediment
3. Habitat (aquatic & terrestrial)
4. Recreation & aesthetics
5. Safe Water Supply
Page 62
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.
Page 65
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
Page 66
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
Page 67
Stream Corridor Longitudinal Profile
Stream Corridor Restoration: Principles, Processes, and Practices.
1998. Federal Interagency Stream Restoration Working Group.
Page 68
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
Page 69
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
Page 70
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
http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/
fluvial_systems/geologic_work_of_streams.html
Page 71
Bedload is related to Discharge for Each River
Page 72
Deposition:
Aggradation: Raising the bed elevation
Bars: Depositional areas that may change flow directions
http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/
fluvial_systems/geologic_work_of_streams.html
Page 73
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
Page 74
Substrate
Characterization
Wolman Pebble Count
Page 75
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
High Slope Moderate Slope Low Slope
Page 76
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
Page 77
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)
Page 78
Stream Competence (www.epa.gov/WARSSS)
Page 79
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
Page 81
Sediment
Deposition:
• Point bar
• Lateral bar
• Mid-channel bar
• Transverse bar
• Delta bar
Page 82
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 83
Point Bars:
Inside meander
bends
Page 84
Lateral Bars:
Formed in
straight channels
Page 85
Lateral Bars:
Formed in
straight channels
Page 86
Mid-channel Bars:
Formed in over-
wide channels
Page 87
Transverse Bars:
Formed in straight
channels
Page 88
Meandering Stream: Alluvial Forms
Point Bar
ScarpBankfull Stage
Thalweg
Flow DownstreamFloodplain
Riffle
Pool
Right
Bank
Left Bank
Page 89
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.
Page 91
Channel
Evolution
(Succession)
Response to
incising forces
Stream Corridor Restoration:
Principles, Processes, and Practices.
1998. Federal Interagency Stream
Restoration Working Group.
Page 93
Incised System: Floodplain Creation
Floodplain
Terrace
Page 94
Stream Morphology:
size and shape of channel & floodplain
(dimension, pattern, profile)
Page 96
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
Page 97
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
Page 98
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
Page 99
Stream Corridor Lateral Profile
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 100
Floodplains: Critical Stream Components
Page 101
Floodplain Functions
• Floodwater storage
• Reducing peak flows
• Erosion prevention
• Water quality
• Groundwater recharge
• Food & shade
• Habitats
Page 103
Floodplain
Left BankRight Bank
Downstream
Terrace
Streambed
Thalweg
Page 104
FloodplainLeft Bank Right
Bank
Downstream
Terrace
Streambed
Thalweg
Page 105
Pool Cross-Section (Meandering Stream)
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 106
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)
Page 107
Dimension (cross-section)
• Area
• Width
• Depth
• Width/Depth Ratio
• Entrenchment Ratio
• Bank Height Ratio
Page 108
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)
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 109
Bankfull
Terrace
Page 110
Dimension: Cross-Section
Page 111
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
Page 112
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
Page 113
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
Page 114
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
Page 115
ER = Wfpa / Wbkf = 75 / 15 = 5.0
Page 116
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
Page 117
Rocky Branch Phase II Reach 1:
Priority 3 (floodplain excavation, Bc channel)
Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2
Page 118
Bank Height Ratio
BHR = LBH / dmbkf
BankfullLBH
dmbkf = Max Depth from bankfull stage to thalweg
dmbkf
LBH = Low Bank Height (Max Depth to thalweg)
Page 119
BHR = 5.3 / 2.5 = 2.1
Page 120
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
Page 121
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
Page 122
Alluvial (low-gradient) streams
naturally meander across a
valley with a somewhat
predictable pattern
Pattern (plan form)
Page 123
Pool
Run
Point Bar
(deposition)
Glide
Riffle
Meandering Stream: Alluvial Forms
Page 124
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 125
Oxbow
Formation in
Meandering
Streams
Stream Corridor Restoration:
Principles, Processes, and Practices. 1998.
Federal Interagency Stream Restoration Working
Group.
Page 126
Chute cutoff across tight meander bend
Page 129
Sinuosity = stream length / valley length
K = 1850 / 980 = 1.9
Valley Length
Page 130
Plan Form Relationships
Page 131
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
Page 132
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
Page 133
Stream Bedform Variability:
Slope Substrate size
Velocity Oxygenation
Shear stress Habitats
Page 134
Riffles
• Steep slope
• High velocity
• High shear stress
• Large substrate
• High porosity
Page 135
Importance of Riffles
• Areas of oxygenation
• Highly diverse substrate and habitat
• Diverse macroinvertebrate population
Page 136
Pools
• Flat slope
• Low velocity
• Low shear stress
• Small substrate
• Scour during high flow
Page 137
Importance of Pools
• Refuge for fish during
low flow, drought
periods
• Rest stop and food
area for fish
• Predator refuge for
young fish
Page 138
River Dimensions
Page 139
Velocities:
Low flow and
Flood flow
Little Garvin
Creek, Clemson, SC
Page 140
Channel dimensions in a meandering stream
www.uwsp.edu/gEo/faculty/lemke/geomorphology/lecture_outlines/04_fluvial_landforms.html
Page 141
Profile is related to Pattern
Page 142
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 143
Step Pool Streams
(high gradient)
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Page 144
Grade Controls
Nickpoints
Page 145
Flow diversity
improves habitat:
• Riffles
• Steps
• Pools
Page 146
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)
Page 147
Equilibrium Controlling Variables
• Width
• Depth
• Slope
• Velocity
• Discharge
• Flow resistance
• Sediment size
• Sediment load
Leopold et al (1964)
Page 148
Channel Forming
Discharges
and Regional
Curves
Page 149
Channel-forming (dominant) discharge
Estimated using:
• Effective discharge
• Bankfull discharge
• Discharge associated with
recurrence interval
(typically 1 to 2 year)
Page 150
Effective Discharge
Transports the
most sediment
over a long time
Page 151
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
Page 152
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.
Page 154
Bankfull Indicators
• Top of streambank (floodplain)
• Break in slope on streambank
• Top of point bar
Bankfull
Bankfull
Page 159
Channel
Evolution
(Succession)
Response to
incising forces
Stream Corridor Restoration:
Principles, Processes, and Practices.
1998. Federal Interagency Stream
Restoration Working Group.
Page 160
Bankfull
Terrace