us army corps of engineers detroit district knife river reducing sediment delivery through forest...
TRANSCRIPT
US Army Corpsof Engineers
Detroit District
Knife River
Reducing Sediment Delivery Through Forest Restoration
US Army Corpsof Engineers
Detroit District
• Drainage Area = 88 mi2
• Mostly forested
• Close to Duluth
• Only naturalized wild steelhead population in MN
• Only MN trib to Great Lakes w/o fish migration barrier
US Army Corpsof Engineers
Detroit District
Knife RiverBackground
Federal Harbor
Knife River is a significant source of sediment to the lake and harbor and has use impairments due to sediment. As such, a TMDL has been established.
US Army Corpsof Engineers
Detroit District
Knife RiverSource of Sediment
Mass Wasting
US Army Corpsof Engineers
Detroit District
Knife RiverThe Problem
The Knife River watershed was historically composed of old-growth red and white pines with some hardwoods. Modern logging activities have replaced those species with a mono-culture of aspen. Local scientists believe that this shift is species has altered the hydrologic response of the watershed resulting in increased flashiness and increased erosion. Local stakeholders are interested in initiating a forest restoration program but would like the following questions answered first:
1.How large of a reduction in sediment delivery is expected if the forest is restored to pre-European settlement species?2.Are some sub-watersheds more sensitive to restoration than others?3.What role does the beaver play in storing sediment and reducing flashiness?
US Army Corpsof Engineers
Detroit District
Knife RiverSummary
• Watershed response to forest restoration modeled with HSPF
• Impact of beaver dams on sediment supplies modeled with RAS
• Hydrologic sensitivity index developed
• Historic flows statistically analyzed
US Army Corpsof Engineers
Detroit District
First Date with Knife RiverTemperature and Precipitation
US Army Corpsof Engineers
Detroit District
Clay-Rich Till Average Slope = 0.8 %
Knife RiverSoils and Topography
US Army Corpsof Engineers
Detroit District
Knife RiverLand Cover and Forest Canopy
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model - HSPF
Tree Age Effect
Hydrologic response following clearing and subsequent
planting of a pine forest at different recovery ages
0 years
2 years
5 years
10 years
20 years
50 years
100 years
Forest Restoration
Re-establishment of mature coniferous forest representative
of pre-European settlement
0%
25%
50%
75%
100%
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model -
HSPF
• Calibrated to Flow at d/s gage
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model – Extent of Forest Restoration
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model – Extent of Forest Restoration
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model – Tree Age
US Army Corpsof Engineers
Detroit District
Knife RiverWatershed Model – Tree Age
US Army Corpsof Engineers
Detroit District
Knife RiverBeaver Influence on Sediment
• Castor canadensis is the largest rodent in North America, growing to 60 lbs over an average life span of 24 years.
• Beaver dams can significantly affect stream flashiness
• Beaver dams can store a large quantity of sediment
• A large pulse of sediment can be mobilized upon breaching
US Army Corpsof Engineers
Detroit District
Intern canadensisCastor canadensis
Knife RiverBeaver Confusion
US Army Corpsof Engineers
Detroit District
Knife RiverBeaver Influence
on Sediment
US Army Corpsof Engineers
Detroit District
Knife RiverSummary of flow at USGS Gage
US Army Corpsof Engineers
Detroit District
Knife RiverFlashiness Index
No Trend
US Army Corpsof Engineers
Detroit District
Knife RiverFlashiness Index
US Army Corpsof Engineers
Detroit District
Knife RiverFlashiness Index
US Army Corpsof Engineers
Detroit District
Hydrologic Sensitivity Index
Ranks hydrologic sensitivity of sub-basins based on slope, distance to outlet and percent disturbed land
US Army Corpsof Engineers
Detroit District
Knife RiverConclusions
• Forest restoration to Pre-European species will have a minimal effect on altering stream flows except in a few sub-watersheds
• Beaver dams will store water and reduce the flashiness of the stream at low flows, but have no effect once the 2-yr flow is exceeded
• Beaver dams only temporarily impound sediment. Larger waves of sediment are likely released when a dam or multiple dams fail
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
US Army Corpsof Engineers
Detroit District
US Army Corpsof Engineers
Detroit District
US Army Corpsof Engineers
Detroit District
Figure 39: Impacts of different beaver dam densities with unsteady flow modeling. a) far downstream cross-section b) downstream cross-setion c) cross-section immedietly downstream of dams d) within beaver dam section e) upstream of beaver dams - The black dashed line indicates time of first dam breach
US Army Corpsof Engineers
Detroit District
US Army Corpsof Engineers
Detroit District