Detroit District Sources of Sediment...US Army Corps of Engineers Detroit District Detachment Why is...

Sources of Sediment

From raindrop impacts to geologic processes

US Army Corpsof EngineersDetroit District

Great Lakes Hydraulics and Hydrology Office


Sediment Production vs Delivery

Sediment Production – The mobilization of sediment from a hill-slope or field (Detachment). The addition of vegetation and other management practices can prevent the production of sediment.

Sediment Delivery – The ability of water (or wind) to pick up (entrain) a particle and deliver it to a stream. Concentrated flow in rills is most important.


Detachment

Detachment – Process in which individual particle are loosened from the soil mass by raindrop impact.

Raindrops impact the soil by breaking physical and chemical bonds, compacting the soil and transporting the soil particles by splash.

The erosivity of rainfall is measured as its kinetic energy (function of drop size and velocity).


From U. of Nebraska-Lincoln, 2008

Detachment


DetachmentWhy is rainfall so destructive to bare soil?

• Raindrops range in size from 1-7 mm in diameter

• Hit the ground at approximately 20 mph

• Dislodged soil particles can splash 3-5 ft away

• The impact of millions of drops on bare soil can be significant

• As much as 90 tons of soil per acre can be mobilized during one heavy rainstorm.

• Most splashed soil does NOT leave the field

Source: Iowa State University


On mild slopes, raindrop impact is the dominant mode of displacement. As slope increases, detachment due to overland flow increases.


Sediment moves towards a stream episodicallyThe sediment train

• add figure

•

Tillage relocates sediment

Sediment trapped in buffer stripsSediment Stored in point bar

Sediment starts hereStorm mobilizes sediment

10-yr flood deposits sediment on floodplain

Storm mobilizes sedimentStorm mobilizes sediment

Sediment Stored in mid-channel bar

Source: Microsoft Live Maps


Surface Sealing• Caused by direct impact of rain drops

• Breaks down soil aggregates

• Fines are sorted out and washed into pores, forming a denser and relatively impermeable layer up to 10 mm thick

• Infiltration capacity reduced by as much as 50% during a single storm

• Crust forms as soil dries

• Loamy sands are particularly susceptible

Source: Iowa St University


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)


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


Rainfall Factors

Intensity: the volume of water per unit time (in/hr)

Duration: how long the storm lasts

short duration – moves sediment only a short distance

long duration – moves sediment further downslope

Energy: a function of droplet size and velocity

Heavy rain (0.6 in/hr) has 30 times the energy of light rain (0.04 in/hr)


Rainfall intensity100-yr frequency, 1-hour duration

Erosivity is a function of both intensity and durationSource: Midwest Climate Center


Sheet and Rill Flow

Sheet Flow• A thin film of water flowing downslope

• Begins once surface depressions are filled

• Shallow flow depth limits entrainment (small shear stresses)

• Can protect against raindrop impact

Rill Flow• Forms when sheet flow becomes concentrated due to topography

• Detachment and transport ability much greater than sheet flow

• Microchannels 2-12 in wide and 12 deep

• Rills generally deepen down-slope


Sheet Flow


Sheet Flow

Source: Selegean, USACE


Rill Flow

Source: soilerosion.net

Source: Van Buren County

Source: Clark SWCD


Rill Flow

Image by M. Mamo, Labels added by UNL



Activities that produce sediment

1. Landuse

Agriculture

Forest Management (logging)

Urban and Construction

2. Channel Incision/erosion

3. Dam Removal


Agricultural Sediments

• Bare soil is biggest producer

• Spring is critical time due to:Degraded crop residue

Recent tillage

Lack of crop canopy


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


Urban Sediments

• Urbanization armors the watershed and reduces the sediment production from upland sources

• Increases peak flows, accelerating bank and bed erosion



Dam Removal Sediments

• Dams contain impounded sediment

• If not removed wisely, they can be a major source of sediment


Dam Removal SedimentsReservoir Drawn Down Slowly



Dam Removal Sediments

Reservoir Drawn Down Slowly



Dam Removal SedimentsProfile Readjustment



Land Uses and Erosion

75

7.50.4 0.04

01020304050607080

Soil Loss (tons/acre/

yr)

Constr

uctio

nRow

Cro

p

Grass

Fores

t

Source EPA, 1973


Sediment Production vs Delivery

Sediment Production – The mobilization of sediment from a hill-slope or field (Detachment). The addition of vegetation and other management practices can prevent the production of sediment.

Sediment Delivery – The ability of water (or wind) to pick up (entrain) a particle and deliver it to a stream. Concentrated flow in rills is most important.


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.


Sediment Delivery

Flat Field

Little or no potential to move sediment from field to stream

Field Stream


Sediment Delivery

Mild Sloped Field

Sediment begins moving off field into stream

Field Stream


Sediment Delivery

Steep Hill Slopes

Sediment rapidly moves off field into stream

Hill Slope Stream


Michigan Relief

Michigan has little topographic relief to drive sediment delivery

…but that wasn’t always the case

Source: Ray Sterner, Johns Hopkins University


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.


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


Source: National Geographic


Appalachian Orogeny and the Death of Hexagonoria

Hexagonoria percarinata

Source: Dorr and Eschman, 1970

Source: Dorr and Eschman, 1970

Devonian Great Lakes(~350 Mybp)


Appalachian Orogeny and the Death of Hexagonoria

Sediment

350 mya

From King, 1977


All sedimentary rock in the Great Lakes originated from eroded

material


Michigan Sedimentary Rock


The importance of a sediment budget

• Need to understand where sediment is coming from before you can select an appropriate model or mitigate technique

Source: Selegean, USACESource: Selegean, USACE


Sediment Budget

Identify and Quantify sources of sediment

• Bank erosion – field measurements

• Overland sediment – modeling

• Close sediment budget with existing flow and sediment measurements, dredging records, etc.


Sediment BudgetBank/Bank Erosion

Compare x-sections over time:

19712008

Source: Michigan Stream Team



Establish Permanent Cross Sections




Bank Pins

Source: Rosgen, 1996


Sediment BudgetBank Erosion – Bank Pins


Sediment BudgetBed Erosion – Scour Chains

Source: Rosgen 2006


Sediment BudgetBed Erosion – Scour Chains



Overland Runoff Sediment from SWAT Model

Source: USACE


Regional Curve from 516 Studies

Source: USACE


Determine Total Sediment out of

Watershed

Source: USGS


Balance Sediment Budget

Sediment Out100 tons/yr

Upland Erosion10 tons/yr

Bed/Bank Erosion90 tons/yr

Source: MTU


Data Sources (partial list)

Historic suspended sediment dataco.water.usgs.gov/sediment

National water information systemwaterdata.usgs.gov/nwis

Climate Datancdc.noaa.gov

National Inventory of Damscrunch.tec.army.mil/nidpublic/webpages/nid.cfm

Soils Datancgc.nrcs.usda.gov/products/datasets

…and others!! (see guidance document)

Sediment Budget


Guidance on Developing a Sediment Budget

Coming soon to:

www.glc.org/tributary

Questions?

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]



Great Lakes Historic Sediment Supplies

Source: USACE

Watershed Location and Drainage Area

Drainage Area = 4700 mi2

Main Channel = 210 mi Source: USACE


Study Goal: Develop sediment budget from pre-European settlement to present

USACE, 1834

Watershed-Sediment Changes in Time

< 1840 – very little human impact

1850 - Intense logging begins

>1850 – watershed converted to ag use

>1850 – dams built to support logging and agriculture


Logging and Sediment

From Dickmann and Leefers, 2003


Study ApproachUS Army Corpsof EngineersDetroit District

• Develop Sediment Yield Model

• Calibrate/validate model for modern flows and landcover

• Rerun with pre-European settlement land cover

Source: USACE

Pre-European Settlement Landcover


Land Cover Change

Pre-development 1992


Land Cover Change

44,000676,000Reference Condition

1992

21,00055,000Pre-Development1830

Total Sediment at

Harbor Mouth

(m3 per year)

Total Soil Erosion in the

Watershed(m3 per year)

Model ConditionsYear

SWAT Land Cover Change Results

Improved Farmland by County

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1850 1870 1890 1910 1930 1950 1970 1990Year

Rat

io

CalhounKalamazooVan BurenBerrienHillsdaleBranchSt. JosephCassSteubenLagrangeElkhartSt. JosephDe KalbNobleKosciuskoWhitleyAverage

Conclusions

Sediment production increased from 55,000 cy/yr to 676,000 cy/yr.

Some streams may still be adjusting to this new sediment regime

Stream instabilities observed today, may have been initiated 150 yr ago

Trying to restore a stream to its original condition may not be possible. Stream restoration goals should be compatible with the present flow and sediment regime

This study may provide insight into pre-European sediment supplies for other areas in the Great Lakes



Rainfall intensity100-yr frequency, 1-hour duration

Source: Midwest Climate Center


Sediment Delivery

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