Soil and Practice Effects
0
2
4
6
8
10
12
14
Soil Loss, tons/acre
Practice
34% Sand
58% Sand
75% Sand
Bare
Mulch+ Grass
SiltFence
SedimentTrap
NCSU Soil ScienceR. A. McLaughlin
Ground Covers: Protect From Droplets
NCSU Soil ScienceR. A. McLaughlin
Mulch Doesn’t Work In Ditches
Mulch piled up atrock check dam.
NCSU Soil ScienceR. A. McLaughlin
Erosion – Even on Flat, Sandy Sites!
NCSU Soil ScienceR. A. McLaughlin
Soft Armor for Gentle Slopes
NCSU Soil ScienceR. A. McLaughlin
Hard Armor for Steep Slopes
NCSU Soil ScienceR. A. McLaughlin
Stream Buffer
Crop Field
Field Runoff: Bypass Through Buffer
Bypass In Ditch
NCSU Soil ScienceR. A. McLaughlin
Stream Buffer Spreader
Crop Field
Sheet Flow
Field Runoff: Spread Across Buffer For Treatment
NCSU Soil ScienceR. A. McLaughlin
Silt Fence: Works but Needs Maintenance!
NCSU Soil ScienceR. A. McLaughlin
Dissipated Flow Deposits Sediment
NCSU Soil ScienceR. A. McLaughlin
Backfill
Sediment controlfabric
2 ft.
2ft. rebar 3 -5
in.
1.5-in PVC pipe
Level Spreaders Can Dissipate Flow: Example
FlowLevel & On Contour
R.A. McLaughlin NCSU Soil Science
Simple Math for Sedimentation
V=((4/3)pi(r3)*(d1-d2)*g)/(2pirz3) OR…larger particles fall faster once
flow is slowed/stopped.
R.A. McLaughlin NCSU Soil Science
Sedimentation: Size Matters
0.01
0.1
1
10
100
1000
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Size (mm)
Set
tlin
g T
ime
(ho
urs
)
Fine sand
Silt
Coarse Clay
R.A. McLaughlin NCSU Soil Science
Sediment Trap (full)
NCSU Soil ScienceR. A. McLaughlin
Sediment Deposit at Basin Inlet
NCSU Soil ScienceR. A. McLaughlin
In Conclusion... Sediment is the #1 cause of surface water
degradation. Soil has to become detached to erode:
cover it up! Water always gathers and becomes more
erosive: protect those waterways! Slow water holds less sediment than fast
water: keep the flows low and ponded wherever possible!
R.A. McLaughlin NCSU Soil Science