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