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 ayers@utk.edu