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Mapping Watershed-scale Streambank Erosion Using EPA-BANCS for Determining TMDLs
Paul Ayers, K. Hensley, D. Wade
Biosystems Engineering & Soil Science
University of Tennessee
K. Swinson (Geosyntec), B. Connell (Trutta) University of Tennessee Alum
Sediment in Streams
• Where does the sediment come from – upland erosion?
– in stream erosion?
• How much sediment comes from these sources?
• Some sediment
TMDLs ignore
streambank erosion
Research Objectives
To develop and demonstrate a rapid watershed-scale data collection method to predict total daily sediment load (TDSL) and total maximum daily load (TMDL) for streambank erosion
• Implement Streambank Video Mapping System (SVMS)
– Map streambank condition
• Utilize Bank Assessment for Non-point source Consequences of Sediment (EPA BANCS) method
– Evaluate erodibility and erosivity – Predict Bank Erosion Rate (BER)
• Utilize flow data – Predict TDSLs and develop TMDLs
Driftwood River
Assessment
• Located in Indiana, adjacent to Camp Atterbury
• Funded by Department of Defense Legacy Program (through Army COE CERL)
• Look at stream bank erodibility
• 12 mile section mapped
Flow
VIDEO CAMERAS
LASERS
SONAR TRANSDUCER
WATERPROOF CASE
Streambank Video Mapping System (SVMS)
GPS Position Depth Width Video
streambank condition
Mapping In Progress
EPA - Watershed Assessment of River Stability & Sediment Supply (WARSSS)
• Bank Assessment for Non-point source Consequences of Sediment (BANCS) model
• BANCS – predicts annual streambank rescission (in/yr) at a sample location (Bank Erosion Rate)
• BER = f (BEHI, NBS) • BEHI – Bank Erosion Hazard Index • NBS- Near-Bank Stress = f(RC/W, etc) • Estimate site-specific annual and total daily streambank
erosion (tons/feet of streambank) • Determine areas of high streambank erosion rates • TMDL determinations
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment
Rc/W
BER
SVMS
USGS flow data
TDSL
Implementing EPA BANCS
Method
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment
Rc/W
BER
SVMS
USGS flow data
TDSL
Implementing EPA BANCS
Method
Modified Bank Erosion Hazard Index (BEHI*)
Based on Connell, 2012
Extreme
Modified Bank Erosion
Hazard
Rating
BankHeight
to Bankfull
Height
(Ratio)
Riparian
Diversity x 2
(%)
Bank
Angle
(Degrees)
Surface
Protection
( %)
Index
Totals
Low Value 1.0-1.19 Optimal 0-60 55-100
Index 2.45 4.9 2.45 2.45 12.2–23.2
Moderate Value 1.2-1.5 Sub Opt 61-80 30-54
Index 4.95 9.9 4.95 4.95 23.2–30.5
High Value 1.6-2.0 Marginal 81-90 15-29
Index 6.95 13.9 6.95 6.95 30.5–38.0
Very High Value > 2.1 Poor > 91 < 14
Index 9 9 9 38.0–45.0 18
0 - 60
=2.45
61 - 80
=4.95
81 - 90
=6.95
> 91
=9 0-1ft 1ft-3ft 3ft - 6ft 6ft-9ft 9ft-12ft 12ft-18ft
100-56
=2.45
55-30
=4.95
29-15
=6.95
< 14
=9
Optimal
=4.9
Sub Opt
=9.9
Marginal
=13.9
Poor
=18
Bank Angle (deg) Bank Height (ft)
Surface Protection
(Avg. %) Riparian Diversity
Bank Angle = 6.95, BH/BF Ratio = 6.95, Surface Protection = 18, Riparian Diversity = 6.95
14:39 14:39 14:39 14:39
BEHI* Score = 38.85
Rating = Very High
12.3 – 23.2 Low 23.2 – 30.5 Moderate 30.5 – 38.0 High 38.0 – 45.0 Very High
Georeferenced Data in ArcGIS BEHI* Total
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment
Rc/W
BER
SVMS
USGS flow data
TDSL
Implementing EPA BANCS
Method
Near Bank Stress (NBS)
Determining NBS from Rc/W:
• Rc = Radius of curvature
• W = River width
• NBS – Categories very low to
extreme
– Values 1 to 6
WARSS, www.epa.gov/warsss
NBS Description
NBS Value
Rc/W
Very Low 1 > 3.0
Low 2 2.21 - 3.0
Moderate 3 2.01 – 2.2
High 4 1.81 – 2.0
Very High 5 1.5 – 1.8
Extreme 6 < 1.5
Stream Erosivity (RC/W)
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment
Rc/W
BER
SVMS
USGS gage data
TDSL
Implementing EPA BANCS
Method
North Carolina Piedmont Region Bank Erosion Prediction Curve
http://www.bae.ncsu.edu/programs/extension/wqg/srp/
Predicting Total Daily Sediment
Load (TDSL)
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment Rc/W
BER
SVMS
USGS flow data
TDSL
USGS Gage Station 03363000
http://waterdata.usgs.gov/nwis/rt
0
500
1000
1500
2000
2500
3000
3500
4000
1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361
Flo
w R
ate
(cf
s)
Julian Day
Average Daily Flow (cfs) for Driftwood River (1942 - 1991)
USGS Stream Gage Data
Estimating:
• Lateral Erosion Rate = f(Q 0.6)
– Q = flow rate
– Based on a power factor (Evans et al., 2003)
• Erosion Potential
– LERi / ∑i LER
http://waterdata.usgs.gov/nwis/rt
Julian Day
Month Number
Day Number Begin Yr End Yr
Mean Flow LER
Erosion Potential
% Erosion Potential
1 1 1 1969 2011 662 49.2623 0.0037 0.3693
2 1 2 1969 2011 578 45.4105 0.0034 0.3405
3 1 3 1969 2011 550 44.0776 0.0033 0.3305
0
0.1
0.2
0.3
0.4
0.5
0.6
0 500 1000 1500 2000 2500 3000 3500 4000
% D
aily
Flo
w E
rosi
on
Po
ten
tial
Flow Rate (cfs)
Flow Erosion Potential vs. Flow Rate
Predicting Total Daily Sediment
Load (TDSL)
BEHI* (erodibility)
NBS (erosivity)
Ocular Assessment
Rc/W
BER
SVMS
USGS flow data
TDSL
From site-specific BER and erosion
potential based on USGS flow data
Predicting TDSL
Estimating Sediment Loads:
• Site-specific daily erosion rate (DER) – BER (ft/yr) x % erosion potential
• Site-specific daily sediment load (DSL) – DER x bank height x bank length x soil density
• Total daily sediment load (TDSL) – ∑ Site-specific DSL
600
800
1000
1200
1400
1600
1800
30-May 31-May 1-Jun 2-Jun 3-Jun 4-Jun 5-Jun 6-Jun 7-Jun 8-Jun 9-Jun
Flo
w R
ate
(cf
s)
Day
Storm Event on the Driftwood River
Flow
0
2
4
6
8
10
12
14
16
18
20
600
800
1000
1200
1400
1600
1800
30-May 31-May 1-Jun 2-Jun 3-Jun 4-Jun 5-Jun 6-Jun 7-Jun 8-Jun 9-Jun
TDSL
(to
ns/
day
)
Flo
w R
ate
(cf
s)
Day
Storm Event on the Driftwood River
Flow
TDSL
Developing Sediment
Total Maximum Daily Load
(TMDL) using EPA BANCS
BEHI* (erodibility)
NBS (erosivity)
Streambank Ocular
Assessment
Rc/W
BER Bank erosion
rate
SVMS
USGS flow data
TMDL For Sediment
TDSL Total daily
sediment load
Developing TMDLs
Using Equation
• Long Term Average (LTA) = µ
– Mean TDSL over a desired time period
• Coefficient of variation (CV) = standard deviation
µ (mean)
• σ2 = ln(CV2+1)
• Recurring interval: 365 days, z score = 2.778
• Maximum Daily Load (MDL) = LTA * e (zσ – 0.5σ^2)
An approach for using load duration curves in developing TMDLs (EPA, 2006)
Developing TMDLs
Driftwood River
• Long Term Average = 13 tons/day – Approximately 980 cfs
• SDev= 5.57 tons/day
• CV = 0.369
• 12mi Reach MDL – 70 tons/day
• MDL flow rate – Approximately 15,200cfs
– Occurs <1% of the time over a 49yr period
Driftwood River Peak Flow Rate
Benefits of Streambank Video Mapping
• Integrate with the EPA BANCS method • Predict erodibility and erosivity • Estimate total annual or daily streambank erosion • Develop TMDL utilizing EPA protocol • Evaluate restoration impacts • Cover large areas (10 miles/day) - continuous • Non-intrusive, no access required • Permanent historical video database • The advantage of video mapping every foot of stream and bank
is that 1) the total daily streambank erosion can be determined, and 2) the locations of high erosion can be identified and managed
Questions?
Contact: Paul Ayers Biosystems Engineering University of Tennessee [email protected]