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Erosion & Sediment Control for
Stream Restoration Projects
Greg Jennings, PhD, PE
Professor & Extension Specialist
Biological & Agricultural Engineering
North Carolina State University
Thanks to Wyatt Brown, LSS, CPESC
NC Ecosystem Enhancement Program
NC Sediment Pollution Control Act, 1973
• 15A NCAC 04B .0105
PROTECTION OF PROPERTY
• Persons conducting land-disturbing activity shall take all reasonable measures to protect all public and private property from damage caused by such activities.
• History Note: Authority G.S. 113A-54(b); 113A-54(d)(2);
• Eff. February 1, 1976;
• Amended Eff. August 1, 1988; November 1, 1984.
1. Site Preparation
2. Grading
3. Structures
4. Site Stabilization
Construction Practices
• Construction entrance
• Silt fence
• Staging & stockpile
• Temporary crossings
• Stream flow diversion
1. Site Preparation
Silt Fence• Metal Posts 8 feet apart
• Reinforcing wire backing (14 ga. w/ 6-inch mesh)
• Bury fence 8 inches deep
Silt Fence
Problems
Silt Fence
Problems
Staging and Stockpile
Stockpile Area
Silt fence &
seeding
Problems?
Temporary Stream Crossing
• Rock ford
• Culvert
• Portable
log mat
Problems?
Prevent erosion
around culvert
Problems?
Stream Flow Diversion
• Open channel
• Pipe
• Pump around
• Work in wet
Open channel
Must dissipate
energy at end
Problems?
Pipe
Pipe Undersized
Pump Around: Match pump to 2 x base flow
Check dam to
retain base flow
Quiet pump in
residential area
Pump
discharge
downstream
Problem?
Special Stilling Basin: Filter Bag
Problem?
Problem?
1. Stage project to limit exposed areas
2. Use temporary ground cover
3. Use track equipment if possible
4. Keep stormwater runoff away from site
2. Grading
Clearing & Grubbing
Followed by Survey Stakeout
Problem?
Problem?
1. Build according to design
2. Check elevations (twice)
3. Footer boulders and backer logs
4. Seal structures to prevent piping
• “Chink” rock structures
• Filter fabric for all structures
3. Structures
Boulder Cross Vane
20-30 degree angles
2-5 % arm slopes
20-30 degrees
2-5 % arm slopes
Laser Level for Grade Check
Log Vane (with
root wad)
Backer Log
Woven filter
fabric nailed to
top log
Geotextile nailed to top log
Overhanging top
log for fish cover
Why do structures fail?
• Rocks or logs not placed properly
• Piping under or through rocks or logs
• Lack of geotextile, improperly placed
• Excess scour
• Poor vegetation & bank stability
Structure Problems
• Wrong Location
• Too Steep
• Not Keyed Into Bank
• Poor Vegetation Establishment
• Not Sealed
Poor placement
and not keyed in
Drop too great
Easy to spot during high flows…
Also easy to spot…
after the flows have receded
Too steep
How about this one?...
Keep log wet…even
at normal daily flow
Too steep
Structural
collapse
Root Wads Too High
Too Few & Washed
Out Behind
Problem?
Problem?
Problem?
4. Site Stabilization
• Temporary ground cover (mulch & matting)
• Permanent ground cover (vegetation)
• Prepare for rain!
Straw Mulch: 75% cover (2 tons/acre)
Hydroseeder
(mulch, seed, f
ertilizer)
Matting
• Biodegradable (coir, jute, excelsior, straw)
• Seed and straw UNDER matting
• Keep matting relaxed
• Stakes: wood or biodegradable plastic
No Plastic!
Each Day:
Seed, straw, ma
tting
Erosion control every day
Large stakes at toe of slope
Problem?
Irrigation
Overland
Flow
Straw Wattle used as Berm
Straw Wattle used as Berm
Site Inspection
Note: Channel stabilized before floodplain
Successful Project:
1. Good design considering hydraulic & sediment
transport processes
2. Communication between designer & contractor
3. Flexibility to make field changes
4. Understanding of environmental regulations
5. Prepare for flooding!
Use Common Sense
Thanks to:
Wyatt Brown, NC EEP
Dan Clinton, Cary
Darrell Westmoreland, North State Environmental
Jan Patterson, Cary, NC