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Poplar River Sediment Source Assessment. John L. Nieber Bruce N. Wilson Department of Bioproducts and Biosystems Engineering University of Minnesota July 17, 2009. Timeline. Impaired for turbidity on Minnesota’s list of impaired waters (2004) - PowerPoint PPT Presentation
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Poplar River Sediment Source Assessment
John L. NieberBruce N. Wilson
Department of Bioproducts and Biosystems Engineering
University of Minnesota
July 17, 2009
Timeline Impaired for turbidity on Minnesota’s
list of impaired waters (2004)MPCA must complete a study to
determine the total maximum daily load (TMDL)
TMDL study was started in 2006, but was not finished at the planned date (2008)
The MPCA requested that the U of M team continue the work and to estimate contributions of erosion sources
Targeted completion of the Draft TMDL is 2011
BackgroundHigh turbidity threatening
trout stream and health of Lake Superior
Turbidity is caused by suspended silt/clay
Poplar River is considered a nonpoint source (both natural and anthropogenic sources of pollution)
Significant streambank and bluff erosion observed; suspected as primary sources
Some measures have been taken to reduce the sediment load in the river (Mega Slump), and revegetation of bare surfaces
Specific Water Quality Problems
When comparing upstream to river mouth loading rates: Phosphorus increased by 2X Total suspended solids (TSS) by
6X Mercury levels exceeded the
state standard Mercury and TSS levels were
strongly correlated Reducing sediment loss rates
in the lower Poplar River will be beneficial for reduction of total mercury quantities into Lake Superior.
“…juvenile [trout] population has declined in the Poplar since 1989.”
Water quality sampling was conducted according to approved MPCA quality assurance procedures (MPCA, 2000)
Comparison of Turbidity at different sites in the
Poplar River
Comparison of Turbidity at different sites in the
Poplar River
Upstream (left) and downstream sites on the Poplar River, July 30, 2001 after a large rainfall (locations are approximately 3 mi apart)
Photo credits: MPCA 2002
114 square miles of drainage area
Lots of upland lakes and wetlands
Soils: red lake clay and Superior lobe till
25.5 miles of river Has the highest
percentage of urban land use of the monitored north shore trout streams (3.5%, mostly in the lower river area)
Stream bed is composed mostly of boulders and cobbles
Objectives (overall)Acquire archived data and assess data gaps;
acquire additional geomorphic data of the river and watershed, and other watershed data
Apply sediment generation and sediment transport models to assess potential sediment sources and their impact on loading and transport within the river
Evaluate and assess the sources of sediment entering and being transported within the Poplar River to Lake Superior
Current Activity (now until 10/30/09)
Acquiring and processing archived channel morphology data for critical sections of the lower Poplar RiverCollected by the Cook County SWCD, MPCA,
and MNDNRData gaps will be assessed and then filled in
within scope of the projectIdentify a reference watershed and stream to
compare sediment generationModeling work plans for future studies will be
formulated
WEPP model (LER, 2005 as listed in 9/2007 report by RTI)
An evaluation of soil type, land use type, and slope was conducted using a geographic information system.
The areas of distinct combinations of soil type, land use type, and slope were calculated for the Poplar River gorge area.
The land use type, soil type, and slope combination were simulated using WEPP.
Ski trails (tall and short grass); bare soils, forest, natural openings, and golf courses were simulated using the WEPP: Hillslope model.
Roads (Lutsen and non-Lutsen) were simulated using WEPP: Roads.
This average of 180 tons/year was compared by RTI (9/2007) to the sediment transported in 2002 which was 1,112 tons/year
WEPP model (LER, 2005 as listed in 9/2007 report by RTI)
WEPP model (LER, 2005 as listed in 9/2007 report by RTI,
9/2007)
WEPP model application by RTI (February 2008)
Estimate erosion from major land uses in lower Poplar River watershed
Used refined resolution of landscape features
Compared results to measured sediment loads
Quantified temporal distribution of loadsConducted sensitivity analysis
WEPP model application by RTI (February 2008)
Limitations of WEPP 2006.5 (watershed version)
Poor simulation of impervious areas Overestimate of erosion and sediment yield
may occur at larger watershed sizesDoes not include bank erosion or sloughing Does not include roads in the watershed version Does not include erosion from perennial
streams Does not simulate gully erosion
WEPP model application by RTI (February 2008)
Results
Average upland source of sediment estimated to be 76% of total load – compared to 20% in LER study
Trends between predicted and observed sediment load similar
Prediction shows that development has significant effect on sediment load
WEPP model application by RTI (February 2008)
WEPP model application by RTI (February 2008)
Expected data needs to fill gapsStream morphology
X-sectionsTexture of bank materialsBank Erosion Hazard Index (BEHI) of banksShear strength of bank materials
Landscape topography – LIDAR, field surveying
Identification of gullies and other concentrated sediment sources
Locations of road and trailsSoil characterization for runoff generation
Future ActivityWatershed modeling will be done to:
Better delineate the upland runoff erosion sources Determine contribution of different sources to
sediment loadField data will be used in three models to provide
estimates of erosion generated from the streambanks and bluffs – CONCEPTS, BSTEM, BEHI
Development of a method to monitor BMP effectivenessTest this method on the Mega Slump
U of M will assist the Cook County SWCD with incorporating the results of these tasks into the TMDL report
Configuring natural flow pathways
Topographic contours
Flow paths in Wisconsin watershed – derived digitally
Configuring natural flow pathways
Flow paths in Oklahoma watershed – derived digitally
Identifying location for erosion/sediment transport potential
tan( )sA
Distribution of unit stream power (watershed in SE Minnesota); from Moore and Nieber (1989)
Unit stream power
Data needs for upland erosion distribution
Detailed topographic dataBedrock depth – soil thicknessSoil hydraulic propertiesErodibility of soilsField verification of connectivity of
sources to ephemeral, intermittent or perennial stream channels
Questions?
Referenceshttp://www.lakesuperiorstreams.orghttp://www.pca.state.mn.ushttp://www.epa.govPoplar River, MN (Cook County), 2006
Automated, in situ, Water Quality Data: Preliminary Analysis