03 sedshortcourse feb10 goodbadugly...us army corps of engineers detroit district figure 3.23:...
TRANSCRIPT
US Army Corpsof EngineersDetroit District
Sediment:The Good, The Bad, The Ugly
Travis Dahl, P.E.U.S. Army Corps of Engineers
US Army Corpsof EngineersDetroit DistrictHow Much Soil Is there?
* These slides were adapted from the website of NASA’s Goddard Space Flight Center.
Water covers ~75% of the Earth’s surface.
US Army Corpsof EngineersDetroit DistrictHow Much Soil Is there?
* These slides were adapted from the website of NASA’s Goddard Space Flight Center.
Half of the dry land is too hot, too cold, or too high to be productive.
US Army Corpsof EngineersDetroit DistrictHow Much Soil Is there?
* These slides were adapted from the website of NASA’s Goddard Space Flight Center.
Of the remaining land, 40% is severely limited by terrain, fertility, or excessive rainfall.
US Army Corpsof EngineersDetroit DistrictHow Much Soil Is there?
* These slides were adapted from the website of NASA’s Goddard Space Flight Center.
Only ~10% of the Earth’s surface is usable for agricultural production.
US Army Corpsof EngineersDetroit DistrictSoils – “Non-Renewable” Resource
There is only a thin veneer of “living”, organic soil in most places on Earth
It takes 500-1,000 years to form 1 inch of soil
We are losing soil faster than it is being produced
US Army Corpsof EngineersDetroit District
Sediment Sources
Wind
Field
Banks
Rill
US Army Corpsof EngineersDetroit District
Sediment Sources: Contribution of Channel Bed
Incision
Small Headcut
Wide Active Channel
Narrow Active ChannelWith Grassed Benches
US Army Corpsof EngineersDetroit District
US Army Corpsof EngineersDetroit DistrictDead River Dam Breach
US Army Corpsof EngineersDetroit District
Exposed Infrastructure
US Army Corpsof EngineersDetroit District
US Army Corpsof EngineersDetroit District
US Army Corpsof EngineersDetroit DistrictWhittlesey Creek - Middle Reach
US Army Corpsof EngineersDetroit DistrictSediment Impact on Fish Habitat
Reduced visibility Damage to fish gills Infilling of habitat Reduction in food supply
* This slide was adapted from the website of Canada’s Department of Fisheries & Oceans
US Army Corpsof EngineersDetroit District
Dredging
US Army Corpsof EngineersDetroit DistrictOntonagon Beach Nourishment
US Army Corpsof EngineersDetroit District
Miller Creek Dredge Spoils
US Army Corpsof EngineersDetroit District
Year Model ConditionsTotal Soil Erosion in
the Watershed(m3 per year)
Total Sediment at Harbor Mouth(m3 per year)
1830 Pre-Development 55,000 21,000
1992 Reference Condition 676,000 44,000
St. Joseph River, MI & INModeled Land Use Change Effects
US Army Corpsof EngineersDetroit District
Figure 3.23: Effect of Dams on Watershed Sediment Delivery
0
100,000
200,000
300,000
400,000
0 50 100 150 200 250 300 350
Distance Upstream from Mouth (km )
Sedi
men
t Del
iver
y (to
nnes
/yea
r)
0
50
100
150
200
250
300
350
400
Crossm ark on Axis Show s Location of Major Dam
Elev
atio
n (m
)
SD w ith Dams SD w ithout Dams Elevation (m)
Influence of Dams
US Army Corpsof EngineersDetroit District
BALANCE BALANCE BALANCE
US Army Corpsof EngineersDetroit District
Knowlton CreekAltered Hydrology = Sediment Starvation
US Army Corpsof EngineersDetroit DistrictThe Good
Erosion
Grassed Bench
Active Channel
US Army Corpsof EngineersDetroit District
Typical Agricultural Ditch Design
Ditches are designed and maintained as trapezoidal channels withflat bottoms
US Army Corpsof EngineersDetroit District
Grass bank Grass Benches Grass Bank
Components of Two-Stage Ditch
Narrow Active Channel
US Army Corpsof EngineersDetroit DistrictConclusions
Soil is a limited resource Keep sediment on the land!
Balance sediment transport, sources, and sinks
Be aware of caches of sediment (dams, lakes, harbors)
US Army Corpsof EngineersDetroit DistrictUS Army Corps
of EngineersDetroit District
Questions?