A Project of the Napa County Resource Conservation District
description
Transcript of A Project of the Napa County Resource Conservation District
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Implementing Sediment and Pathogen TMDLs in the North Bay: Napa River Watershed
Leigh Sharp, Executive DirectorNapa County Resource Conservation District
November 4, 2012
A Project of the Napa County Resource Conservation Districtin collaboration with North Bay Watershed Association and San
Francisco Estuary Partnership with funding from the US EPA San Francisco Bay Water Quality Improvement Fund
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Napa River TMDL Information
• Listed for sediment, nutrients, pathogens
• TMDLs adopted for sediment and pathogens
• Sources of sediment– Channel incision & bank erosion,
roads, gullies, and sheet erosion– associated with vineyards, grazing,
rural lands, parks and open space, and public works
• Sources of pathogens – On-site sewage disposal systems,
sanitary sewer systems, municipal runoff, grazing lands, confined animal facilities
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Major Project Tasks
Implement Sediment TMDL in Napa River Watershed– Conduct outreach– Complete rural road assessments– Implement road improvements in
Heath Canyon watershed
Implement Pathogen TMDL in Napa River Watershed– Conduct outreach and education to
land managers with confined animal facilities
– Implement identified projects to manage runoff & erosion
Coordinate with other NBWA partnersWatershed Monitoring
– Sediment and fisheries related monitoring
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Roads influence the hydrology of a watershed
• Poorly constructed and maintained roads concentrate runoff, increase erosion, and potentially deliver sediments to streams
• Studies demonstrate that up to half of all anthropogenic sediment entering streams comes from road-related erosion
Accomplishments to Date: Road Treatments
Humboldt County
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Excess sedimentation and increased runoff impairs stream function
May:• Pollute water
supplies• Increase potential
for flooding• Accelerate stream
bank erosion and trigger landslides
• Erode or harm riparian vegetation
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Excess sedimentation impairs aquatic habitat
• Suffocates fish eggs in spawning beds• Loss of aquatic habitat
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Our goal is to treat roads with practices that are safe for travel and most mimic nature
Nothing in nature mimics a road……but roads are necessary
China
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Sediment delivery from road-related erosion can be episodic or chronic
• EPISODIC sediment delivery– Sediment delivery is episodic when it occurs as soils fail in response to
storm events or other triggers. The delivery from a site may occur once, or in pulses over an indeterminate time period. Stream crossing washouts, road-related landslides, and gullying can produce episodic sediment delivery.
• CHRONIC sediment delivery– Sediment delivery from road surfaces and cutbanks is chronic because it
occurs continuously during rainfall events that produce surface runoff
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Culvert
Natural stream grade
Road fill
Road surface
Episodic sediment delivery results from poorly designed stream crossing
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Aggraded sediments above inlets can cause crossings to wash out
Napa County
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Channel scours below outletNapa County:
treated by RCD in 2009
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Stream crossing fails and produces episodic sediment delivery
Napa County: treated by
RCD in 2009
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Low impact design for a culverted stream crossing on a non-fish bearing stream
CulvertNatural stream grade
Road fill(2:1 slope)
Road surface (4% outslope)Trash rack
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Fail-safe features impede plugging of culverts and prevent sediment delivery if crossing floods
Napa County: treatments in 2010
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Examples from Heath Canyon Work
treated in 2011
Old culvert inlet
New inlet setat grade
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Examples from Heath Canyon treatments
Old culvert outlet
New outlet set in at base of fill
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Old culvert outlet
New outlet set in at base of fill
New inlet setat grade
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Armored fill crossings may be
sufficient on seasonal-use
roads
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Sediment delivery from road-related erosion can be episodic or chronic
• EPISODIC sediment delivery– Sediment delivery is episodic when it occurs as soils fail in response to
storm events or other triggers. The delivery from a site may occur once, or in pulses over an indeterminate time period. Stream crossing washouts, road-related landslides, and gullying can produce episodic sediment delivery.
• CHRONIC sediment delivery– Sediment delivery from road surfaces and cutbanks is chronic because it
occurs continuously during rainfall events that produce surface runoff
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Fine sediments are generated as vehicles mechanically break down the road surface
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This is what happens to that powdery dust when
it rains
Napa County
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Physical features show surface lowering over time
Exposed culvert
Napa County: treated by RCD
in 2011
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Shape of road surface can concentrate flow and promote erosion
Berm
Runoff
Before
Napa County: treated by RCD in
2009
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Low impact road surface design disperses flow across the landscape
Ditchremoved Berm
removedRunoff
After
Rolling dip
OutslopingNapa County: treated by RCD in
2009
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Examples from Heath Canyon Work treated in 2011
Runoff
Runoff
Rolling Dips
Road runoff from both roads delivering to a gully and a
stream
Road runoff from side road treated separately, runoff dispersed via rolling dips
(away from gully and stream)
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Before
Runoff
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After
Runoff
Rolling Dip
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Preliminary Numbers
• 6,144 yd3 of sediment delivery to waterways avoided
• 4.71 miles of road treated
• 32 stream crossings upgraded
• 83 rolling dips installed
Napa County: No treatment needed
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Use the right tool for the job
Napa County: RCD treatments 2009-2011
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Plan for cultural resources too
Napa County: RCD Treatments 2011
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Additional Funding Partners
• California Department of Fish and Game
• Napa County (Measure A)
• California Department of Conservation
• Private Landowner
Napa County: treatment by RCD in 2010
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Next Steps……
• Complete additional road assessments
• Work with rural landowners with confined animals
• Develop more QAPPs