Erosion-Sedimentation - Montana State University - Extension Water ...

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21 Φεβ 2014 (πριν από 3 χρόνια και 6 μήνες)

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Erosion ↔
Sedimentation
Cut and Fill in the Landscape
The Chicken or the Egg
Jim Bauder and Adam Sigler
Montana State University
Extension Water Quality
2
Presentation Outline

W
hat are Erosion and Sedimentation?

U
nderstanding the Processes

S
ources and Sinks

I
mplications: The Good, The Bad, The Ugly

M
ethods of Quantification

M
ethods for Management (BMPs)
3
First the Earth’s Surface is Lifted
1. Copyright © Okla
homa University
2. Courtesy E.
Lyendecker, United States Geological Survey
3. Photo court
esy of USDA NRCS
4
Then Gravity Does It’s Work
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California storm runoff carries
heavy sediment loads into the
Pacific
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A tsunami in Indonesia causes
catastrophic erosion and
sedimentation effects
7
Definitions of Processes

Erosion: the removal of soil, sediment,
regolith, and rock fragments
from the landscape.

Sedimentation: the deposition of
transported material in a new
location
.
8
Relationship: Cause and Effect
Photo court
esy of USDA NRCS
Photo court
esy of USDA NRCS
Severely Eroded Hillside
Sediment Choked Stream
9
Types of Water Erosion
Sheetwash
Rainsplash
Rilling
Photos courtesy of USDA NRCS
10
Types of Water Erosion
Gullies
In-Stream
•Bank Scour and Slough
•Bottom Scour
Piping
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Types of Wind Erosion
Wind Erosion Starts when wind speeds reach about 10 mph

T
raction or Creep: a rolling motion of particles

S
altation: when particles are lifted and deposited
several centimeters away; upon landing they
strike and can dislodge other particles

S
uspension: when smaller particles are lifted and
transported long distances
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The Process of Sedimentation

Transport is
Velocity
Dependent

Larger
Particles
Drop out
First
13
Where does Sedimentation occur?
Floodplains
Pointbars/Lower
Gradient Areas
Flatwater
•Reservoirs
•Lakes
•Oceans
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Sources and Sinks
Mass Balance
Erosion
removes
sediment
from sources
Sedimentation
unloads
sediment at
sinks

15

Lowlands: Fields, Pastures

Ag Practices

Highway Construction

Highway Water Runoff
Sources
Photos courtesy of USDA NRCS
16
Sources

Uplands: Range, Forests
–L
i
v
e
s
t
o
c
k

Timber Harvest
–F
i
r
e
s

Recreation
17
Sources

I
n Channel

N
atural: point bars, banks, substrate

Large Magnitude Storm Events

E
xternalities
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Cut-Fill-Cut: a Circular Process
Source to Sink to Source
1
2
3
4
5
6
7
peneplane
development
19
Sinks

Lakes and Reservoirs

Oceans: Deltas, Beaches

Each Year the Mississippi River deposits 250 million tons of
sediment into the Gulf of Mexico.
http://co.water.usg
s.gov/se
dim
ent/conc.f
rame.html#HDR3
Mississippi River Delta
visualizingearth.ucsd.edu
Credit Line: Copyright © Oklahoma Universit
y
20
Sinks

I
n Channel

P
oint Bars

L
ow Gradient areas

C
onfluence Areas
Confluence of Muddy

Creek an
d Sun River
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Sinks

Floodplains and Irrigated Land

Flood water spills from Obion River in Central Tennessee.
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Implications
The Good, The Bad, The Ugly
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Erosion: The Ugly

10 People Killed, 13 Homes Dest
royed in La Conchita Slide
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Erosion: The Ugly
California Weather Crisis
Normally dry soil was so saturated
that it could no longer absorb the
downpours, resulting in rockfalls

and m
udslides.
25
Sedimentation: The Ugly

Mess left after Missouri River Floodwaters Receded
Photo Courtesy o
f USDA NRCS
26
Sedimentation: The Ugly
Mining sediment in Milltown
reservoir releases up to 7,300
pounds of arsenic, 647 tons of
iron, and 1,250 tons of
manganese into the
groundwater each year.
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/Milltown
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Missoulian
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Erosion: The Bad
In the United States 17 million acres of formerly tilled
land have been destroyed or so badly washed that
farmers can not afford to reclaim them.
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Erosion: The Bad

Loss of Productive Soil

In the US a total
of 108 million
acres are eroding
excessively,
resulting in 1.3
billion tons of
erosion per year.
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Sedimentation: The Bad

Loss of Reservoir Capacity and Siltation
of Irrigation Ditches

A watershed dam in northwest Iowa is completely
silted in and can no longer store floodwaters.
Photo Courtesy o
f USDA NRCS
30
Sedimentation: The Bad

Example:

Inflow
=

3 months x 300 cfs x 300 mg/L = 66,500 tons/yr

9 months x 100 cfs x 100 mg/L = 2,500 tons/yr

Outflow =

12 months x 150 cfs x 50 mg/L = 7,500 tons/yr

Sedimentation = 61,500 tons/yr

Approximately 90 acre feet lost storage per year
Photo Courtesy o
f USDA NRCS
31
Sedimentation: The Bad

Sedimentation and
scour of spawning
gravel have been
shown to cause 50 to
90% mortality in
Salmonid egg pockets.

Habitat degradation is
consistently listed as a
leading cause of fish
population declines.
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Erosion: The Good

Scenic Beauty and Exploration
Photo Copyright © Lar
r
y Fellows Arizona Geological Survey
33
Erosion: The Good

Topography: water delivery,
recreation, orientation
Photo Courtesy o
f USDA NRCS
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Sedimentation: The Good

Floodplains and productive soils
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Sedimentation: The Good

Deltas, Sandbars, Beaches

Map of Natural History
Scorpion Fossils
Photos Copyright © Oklahoma University
36
Methods of Erosion Quantification

R
USLE2:
Revised Universal Soil Loss Equation

W
EPP: Water Erosion Prediction Project

G
IS: Digital Elevation Model based
Programs

W
EPS: Wind Erosion Prediction System
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Plot Isolation/Runoff Sampling
Rainfall Simulator
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MSU x NRCS x
Conservation District
Vegetative Filter Strip
Sediment and Bacteria
Removal Research
38
RUSLE2 FACTORS
Daily Soil Loss = a = r k l s c p
Daily Factors

r
-
R
ainfall/Runoff

k
-
S
oil erodibility

l
-
S
lope lengths -
S
lope steepness

c
-
C
over-management

p
-
S
upporting practices
Average annual soil loss = sum of daily soil loss values
http://fargo.nserl.purdue.edu/rusle2_dataw
eb/
RUSL
E
2_
Training_
Slide_
Set.htm
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WEPP EROSION PREDICTION MODEL
Input Parameters

S
oil Characteristics

S
lope

C
limate

I
rrigation Method and Quantity

C
hannel Characteristics

C
hannel Impoundments

W
atershed Structure

M
anagement Practices
http://topsoil.nserl.purdue.edu/ns
erlweb/weppmain/docs/chap1.pdf
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WIND EROSION PREDICTION SYSTEM
E = f (I, K, C, L, V)

E
= potential average annual soil loss

I
= soil erodibility index

K
= soil ridge roughness factor

C
= climate factor

L
= unsheltered distance across a field

V
= equivalent vegetative cover
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Sedimentation Quantification

WEPP: Water Erosion Prediction Project

Watershed Impoundment Component

Particle size

Impoundment size

Inflow rate

Outflow rate
www.
neaq.
org/
.../ aqu
acult
u
re/lobst
erimpact
.
h
tml
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Sedimentation Quantification

Sediment Cores

History of
Sedimentation

Sources of
Sediment
www
.neaq.o
rg/.../ aquaculture/lobsterimpact.html
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Quantifying Sediment Transport

S
tream Monitoring

C
oncentration x Flow = Load
44
Making Sense of Data
Muddy Creek
Sediment vs. Flow
Relationship 2002
Muddy Creek
Sediment vs. Flow
Relationship 2003
45
What Concentrations Look Like
1000 mg/L
10 mg/L
100 mg/L
=1200 kg/acft
=2600 lbs/acft
= 12 kg/acft
= 26 lbs/acft
= 120 kg/acft
=260 lbs/acft
46
What can we do?
Best Management Practices (BMPs)
& Best Engineering Practices (BEPs)
Photo Courtesy o
f USDA NRCS
47
Erosion BEPs

Armored Stream Crossings

Fenced
Livestock
Watering Areas

Off-Stream
Watering

Relocation of
Animal Feeding
Operations
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Erosion BEP

Armored Banks
Stream Barbs
Grade Stabilization
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Erosion BMP

Embankment Mulching
Reseeding After Fire
Wattle Installation
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Erosion BMP

Conservation Tilling
sca
r
ab.
m
s
u
.
montana
.edu/
Sa
w
f
ly
/
m
anage
m
ent
.htm
51
Erosion BMP

Conversion from Flood
to Sprinkler Irrigation
Washington State Ag Watershed Erosion Study
In a watershed where 15% of irrigated land was converted
from furrow to sprinkler irrigation over 13 years, sediment
runoff decreased more than 30%.
The Study also suggested a decrease in runoff of Pesticides
and Nitrogen with the conversion.
J
E
Q
Ma
r
c
h/Ap
r
il
1998; So
il Pro
c
esses

a
nd Che
m
ica
l

T
r
anspo
rt;
Jame
s C
.

Ebbe
rt
and
Moon H. Kim
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Erosion BMP

Maintain Vegetative Filterstrips
VFS width
15 feet
30 feet
% Reduction
__________________________________________
Sediment
96%
98%
Fecal coliform
75%
91%
Fecal streptococci
68%
74%
53
Conclusion

Erosion and Sedimentation are natural
processes which are easily set out of
balance by lack of appropriate
management.

Methods exist to control sedimentation.
However, the most effective way to
stop excessive sedimentation is to treat
the cause and address the erosion
source.
Photo Courtesy o
f USDA NRCS
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Conference Topics

Sediment and Montana Water Quality Standards

Agricultural BMPs Addressing Erosion

Sediment Monitoring and Assessment

some case studies

Sediment Sourcing, Tracking,
and In-Stream Management

Watersheds, Stream Channels,
and Sediment Dynamics

The Realities of Defining, Dealing With,
and Managing Sediment:
Muddy Creek, Missouri River, Thompson Creek

Predictions, Prediction Tools and Modeling the
Sediment Processes

Poster Presentations
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