Post on 05-Jun-2020
Sediment and River Features
Where does sediment come from?
Why do we care about sediment?
Overview of river features
US Army Corps of Engineers
Detroit District
Great Lakes Hydraulics and Hydrology Office
US Army Corps of Engineers
Detroit District
Sediment Sources
• River Bank Erosion
• Overland Runoff Erosion
Source: Iowa State Extension
Source: Geograph.org.uk
US Army Corps of Engineers
Detroit District
From U. of Nebraska-Lincoln, 2008
Overland Runoff Erosion Detachment
US Army Corps of Engineers
Detroit District
On mild slopes, raindrop impact is the dominant mode of displacement.
As slope increases, detachment due to overland flow increases.
US Army Corps of Engineers
Detroit District
Soil Erodibility
Texture and Particle Size Affect Erodibility
• Silt is most easily eroded component. Loess sediments are
particularly susceptible. (0.004mm - 0.062mm)
• Clays are cohesive and tend to remain bound to the soil
structure; however, once detached they remain in in suspension
(<0.004mm)
• Sand is relatively large and difficult to entrain. Sand also
promotes infiltration (0.062mm - 2mm)
• Organic matter increases infiltration and builds soil structure
(blocky or platy nature)
US Army Corps of Engineers
Detroit District
Factors Affecting Soil Loss
Rainfall – intensity, duration and energy
Soil Erodibility – texture, structure, organic matter content
Topography – slope length and steepness
Surface Condition – bare soil, vegetated, mulched
Erosion Control Practices – sediment basin, silt fences, terracing,
contour planting
Source: Michigan State University, IWR
ErosivityyErodibilitErosionBank
Lateral
Movement of
bank.
Measured in
feet/year
Resisting Force
Intrinsic property
of bank.
Function of:
Soil
Vegetation
Bank Angle
Etc.
Eroding Force
Property of the
hydraulics.
Function of:
Near Bank Shear
Stress
Stream Bank Erosion
US Army Corps of Engineers
Detroit District
Stream Bank Erosion
Source: Rosgen 1996
US Army Corps of Engineers
Detroit District
Activities that produce sediment
1. Landuse
Agriculture
Forest Management (logging)
Urban and Construction
2. Channel Incision/erosion
3. Dam Removal
US Army Corps of Engineers
Detroit District
Agricultural Sediments
• Bare soil is biggest producer
• Spring is critical time due to:
Degraded crop residue
Recent tillage
Lack of crop canopy
US Army Corps of Engineers
Detroit District
Forest Sediments
• Very low sediment yield in closed forest
• Sediment sources are:
Logging roads
ATV trails
Flashier hydrograph (bank erosion)
Bare soil due to logging activities
US Army Corps of Engineers
Detroit District
Urban Sediments
• Urbanization armors the watershed and reduces the
sediment production from upland sources
• Increases peak flows, accelerating bank and bed
erosion
Source: Selegean, USACE
US Army Corps of Engineers
Detroit District
Dam Removal Sediments
• Dams contain impounded sediment
• If not removed wisely, they can be a major source of
sediment
US Army Corps of Engineers
Detroit District
Dam Removal Sediments Reservoir Drawn Down Slowly
Source: Selegean, USACE
US Army Corps of Engineers
Detroit District
Dam Removal Sediments Profile Readjustment
Source: Selegean, USACE
US Army Corps of Engineers
Detroit District
Land Uses and Erosion
75
7.50.4 0.04
0
10
20
30
40
50
60
70
80
Soil Loss
(tons/acre/
yr)
Con
stru
ctio
n
Row
Cro
p
Gra
ss
Fores
t
Source EPA, 1973
US Army Corps of Engineers
Detroit District
From FISRWG, 1998 and Schumm, 1977
Sediment Delivery
Sediment Delivery is driven
by Gravity
• Just like water, sediment
will flow downhill until
deposited into the Great
Lakes
• Sediment sitting at a
higher elevation than the
lakes has potential energy
stored in it
• The higher the change in
elevation, the greater the
energy stored in each
particle.
US Army Corps of Engineers
Detroit District
Sediment Delivery
Flat Field
Little or no potential to move sediment from
field to stream
Field Stream
US Army Corps of Engineers
Detroit District
Sediment Delivery
Mild Sloped Field
Sediment begins moving off field into stream
Field Stream
US Army Corps of Engineers
Detroit District
Sediment Delivery
Steep Hill Slopes
Sediment rapidly moves off field into stream
Hill Slope Stream
US Army Corps of Engineers
Detroit District
Sediment Delivery Slope Matters
US Army Corps of Engineers
Detroit District
Great Lakes Relief
Around the Great
Lakes, there is little
topographic relief to
drive sediment delivery
…but that wasn’t always the case
Source: Ray Sterner, Johns Hopkins University
US Army Corps of Engineers
Detroit District
Historic Relief in Michigan
From Dorr and Eschman, 1970
Penokean orogeny build this range during Middle
Precambrian (1640 million years ago). This range has long
since eroded away.
US Army Corps of Engineers
Detroit District
Mountain Building – high sediment yield
Mountains Eroding –
moderate sediment yield
Mountains gone – Low relief, low sediment yield
Erosion Cycle
Drawings from Dorr and Eschman, 1970
US Army Corps of Engineers
Detroit District
Source: National Geographic
US Army Corps of Engineers
Detroit District
Appalachian Orogeny and the Death of
Hexagonoria
Hexagonoria percarinata
Source: Dorr and Eschman, 1970
Source: Dorr and Eschman, 1970
Devonian Great Lakes
(~350 Mybp)
US Army Corps of Engineers
Detroit District
Appalachian Orogeny and the Death of
Hexagonoria
350 mya
From King, 1977
Sediment – The Good and the Bad
All erosion is NOT bad! Without erosion, we would not
have:
Pools for the big fish to hide in
Overhanging trees to shade the stream and provide refuge
Scoured material to build riffles with
Erosion can be natural – Grand Canyon!
Erosion becomes a problem when:
we build our infrastructure too close to the stream
we cause is to accelerate through our management of the
water and sediment supplies
Reduced visibility
Damage to fish gills
Infilling of habitat
Reduction in food supply
Increase temperature
* This slide was adapted from the website of Canada’s Department of Fisheries & Oceans
Sediment – The Good and the Bad Sediment Impact on Fish Habitat
Sediment – The Good and the Bad
Stream “Stability”
Definition of Stability: The tendency of a stream to
maintain its cross-section, planform and profile
geometry over time, effectively transporting its water
and sediment supply without aggrading (building up),
degrading (down-cutting)
Erosion occurs in a Stable stream
US Army Corps of Engineers
Detroit District
Stream Stability Lane’s Diagram
Source: Rosgen, 1996
There is only a thin veneer of “living”, organic soil
in most places on Earth
It takes 500-1,000 years to form 1 inch of soil
We are losing soil faster than it is being produced
Sediment – The Good and the Bad Soils are Non-Renewable
Sediment – The Good and the Bad Aggradation on Whittlesey Cr
Sediment – The Good and the Bad Exposed Infrastructure
Sediment – The Good and the Bad Aggradation Increases Flooding
Source: USACE - ERDC
US Army Corps of Engineers
Detroit District
Sediment moves slowly and episodically The sediment train
• add figure
•
Tillage relocates sediment
Sediment trapped in buffer strips Sediment Stored in point bar
Sediment starts here
Storm mobilizes sediment
10-yr flood deposits sediment on floodplain
Storm mobilizes sediment
Storm mobilizes sediment
Sediment Stored in mid-channel bar
Source: Microsoft Live Maps
US Army Corps of Engineers
Detroit District
Sediment moves slowly and episodically St. Joseph River – Normal Flow
US Army Corps of Engineers
Detroit District
Sediment moves slowly and episodically St. Joseph River – 2-yr Flow
US Army Corps of Engineers
Detroit District
Sediment moves slowly and episodically St. Joseph River – 5-yr Flow
US Army Corps of Engineers
Detroit District
Sediment and High Flows
Most sediment moves during the largest few flow events
each year
Year
Model Conditions
Total Soil Erosion in
the Watershed
(m3 per year)
Total Sediment at
Harbor Mouth
(m3 per year)
1830
Pre-Development
55,000
21,000
1992
Reference Condition
676,000
44,000
Historic Sediment Supplies St. Joseph River
US Army Corps of Engineers
Detroit District
Stream Features
Source: North Carolina Sea Grant
Source: West Virginia DEP
US Army Corps of Engineers
Detroit District
Stream Features
Source: Michigan Stream Team
US Army Corps of Engineers
Detroit District
Stream Features
Riffles – Steep and shallow; poorly defined thalweg (deepest spot across);
riffles control the flow in a stream (hydraulic choke point); usually found in
straight reaches; this is where your canoe usually rubs bottom.
US Army Corps of Engineers
Detroit District
Stream Features
Pools – Deepest spot along a reach; Water-surface is nearly
flat; Often has large bed material at the bottom; often located at
the outside of meander bends
Source: EPA
US Army Corps of Engineers
Detroit District
Stream Features
Runs – Steep, but much deeper than riffles (steep and deep);
usually have a well defined thalweg; it is said that water “runs”
smooth through a run (as opposed to with ripples in the riffle);
smaller fish are often found here since they can’t yet compete
for the pools.
US Army Corps of Engineers
Detroit District
Stream Features
Glides – Located immediately downstream of the pool; Adverse
bed slope; water has to accelerate to get “uphill” often resulting
in gravel beds free of fine material (spawning beds)
Source: Rosgen
US Army Corps of Engineers
Detroit District
Stream Features
You run into a pool and glide out.
US Army Corps of Engineers
Detroit District
What Moves Sediment?
Shear Stress
τ = γ•s•d
Shear Stress = Unit wt water x slope x depth
Velocity Profile
No Friction With Friction
Pool
Riffle
Riffle
d=high
Slope = very low
Low Flow
Shear Stress
(Sediment Transport)
Low-Moderate
Shear Stress
(Sediment Transport)
Very Low
τ = γ•s•d
Pool
Riffle
Riffle
d = very high
d = moderate
Shear Stress
(Sediment Transport)
High
Shear Stress
(Sediment Transport)
Very High
τ = γ•s•d
High (bankfull) Flow
Pool
Riffle
Riffle
d=high
Receding Flow
Shear Stress
(Sediment Transport)
Moderate
Shear Stress
(Sediment Transport)
High
τ = γ•s•d
Pool
Riffle
Riffle
d=high
Slope = very low
Low Flow
Shear Stress
(Sediment Transport)
Low-Moderate
Shear Stress
(Sediment Transport)
Very Low
τ = γ•s•d
Pool
Riffle
Riffle
d=high
Slope = very low
Low Flow
Shear Stress
(Sediment Transport)
Low-Moderate
Shear Stress
(Sediment Transport)
Very Low
τ = γ•s•d
Sediment in storage
Pool
Riffle
Riffle d = very high
d = moderate
Shear Stress
(Sediment Transport)
High
Shear Stress
(Sediment Transport)
Very High
τ = γ•s•d
High (bankfull) Flow
Sediment in
transport
Pool
Riffle
Riffle
d=high
Receding Flow
Shear Stress
(Sediment Transport)
Moderate
Shear Stress
(Sediment Transport)
High
τ = γ•s•d
Sediment in
storage
Sediment in
transport
Pool
Riffle
Riffle
d=high
Slope = very low
Low Flow
Shear Stress
(Sediment Transport)
Low-Moderate
Shear Stress
(Sediment Transport)
Very Low
τ = γ•s•d
Sediment in storage
Questions?
US Army Corps of Engineers
Detroit District
Pool
Riffle
Riffle Slope = very low
Low Flow
Shear Stress
(Sediment Transport)
Low-Moderate
Shear Stress
(Sediment Transport)
Very Low
Bedload and Suspended Load
Pool
Riffle
Riffle
Shear Stress
(Sediment Transport)
High
Shear Stress
(Sediment Transport)
Very High
τ = γ•s•d
High (bankfull) Flow
Bedload and Suspended Load
Pool
Riffle
Riffle
d=high
Receding Flow
Shear Stress
(Sediment Transport)
Moderate
Shear Stress
(Sediment Transport)
High
τ = γ•s•d