river bank erosion

Detroit District, Hydraulics & Hydrology OfficeUS Army Corpsof Engineers

River Bank Erosion

Siskiwit River, Cornucopia, WI


How Do we Measure Bank Erosion?


The Big Questions…continued

• Are there simple methods that can be used to estimate bank erosion rates in the field?

• Are there simple methods that can be used to estimate bank erosion rates in the field?

Answer…NoAnswer…No


ErosivityyErodibilitErosionBank

Lateral Movement of

bank.

Measured in feet/year

Resisting Force

Intrinsic property of bank.

Function of:Soil

VegetationBank Angle

Etc.

Driving Force

Property of the hydraulics.

Function of:Near Bank

Shear Stress

Bank Erosion


Bank Erodability

How do we determine how susceptible a bank is to erosion?

How do we determine how susceptible a bank is to erosion?



Predicting Bank Erosion

Bank Erosion

Hazard Index (BEHI)


• Bank Height Ratio

• Root Depth Ratio

• Weighted Root Density

• Bank Angle

• Surface Protection

• Bank Material

• Stratification

• Bank Height Ratio

• Root Depth Ratio

• Weighted Root Density

• Bank Angle

• Surface Protection

• Bank Material

• Stratification

BEHI Variables


Low Erosion Potential

Black River, Michigan (UP)


Moderate Erosion Potential

Coldwater Creek, Union City, Michigan


Very High / Extreme Erosion Potential

Ontonagon River, Michigan (UP)



Bank Erosion

Bank Erosion

Hazard Index (BEHI)

Near Bank Stress (NBS)

Index


NBS#1 - Channel Patterns

• Transverse and/or central bars – short and/or discontinous

– NBS = High or Very High

• Extensive deposition

– NBS = Extreme

• Chute cutoffs, down-valley meander migration, converging flow

– NBS = Extreme

• Transverse and/or central bars – short and/or discontinous

– NBS = High or Very High

• Extensive deposition

– NBS = Extreme

• Chute cutoffs, down-valley meander migration, converging flow

– NBS = Extreme


NBS#2 – Ratio of Radius of Curvature (Rc) to Bankfull Width (Wbkf)

Rc/Wbkf Rating

> 3.00 Very Low

2.21 – 3.00 Low

2.01 – 2.20 Moderate

1.81 – 2.00 High

1.50 – 1.80 Very High

< 1.50 Extreme

Generally Rc Performed Using Aerial PhotographyGenerally Rc Performed Using Aerial Photography


NBS#3 & #4 – Ratio of Pool Slope to Average Slope (Sp/S) or Riffle Slope (Sp/Srif)

Sp/Srif Rating

< 0.40 Very Low

0.41 – 0.60 Low


0-81 – 1.00 High

1.01 – 1.20 Very High

> 1.20 Extreme


dnb/dbkf Rating

< 1.00 Very Low

1.00 – 1.50 Low


1.81 – 2.50 High

2.51 – 3.00 Very High

> 3.00 Extreme

NBS#5 – Pool Depth to

Average Depth


Measuring Bank Erosion



Bank Erosion

Bank Pins & Bank Profiles

Bank Erosion

Hazard Index (BEHI)

Near Bank Stress (NBS)

Index


Bank Profile Measurement

Equipment

• Toe Pin (rebar)

• Toe Pin Cap

• Hammer

• Survey Rod (2) or

• Survey Rod & Pocket Rod

• Line Level

• Rod Level

• Field Forms

Equipment

• Toe Pin (rebar)

• Toe Pin Cap

• Hammer

• Survey Rod (2) or

• Survey Rod & Pocket Rod

• Line Level

• Rod Level

• Field Forms


Measuring Bank Profile

Source: Arkansas Department of Environmental Quality


Comparison of Bank Profiles


Bring it all

Together

Regional Curves


Great Lakes Curves - Preliminary


Is there a better correlation for predicting bank erosion?

• Remotely-sensed data

• Radius of curvature

• Meander wavelength

• Beltwidth:valley width

• Valley slope

• Soils maps for resistance and infiltration

• Remotely-sensed data

• Radius of curvature

• Meander wavelength

• Beltwidth:valley width

• Valley slope

• Soils maps for resistance and infiltration


Questions?

Contact: Dr. Jim Selegean, P.E., P.H.

U.S. Army Corps of Engineers, Detroit DistrictGreat Lakes Hydraulics and Hydrology Office

477 Michigan AveDetroit, MI 48226

313.226.6791

[email protected]

river bank erosion

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