Erosion & Sediment Control for

Stream Restoration Projects

Greg Jennings, PhD, PE

Professor & Extension Specialist

Biological & Agricultural Engineering

North Carolina State University

jenningsenv@gmail.com

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