Chapter 7

Nonfarm Erosion Control

7-1

Introduction

• Soil is also disturbed by home building, industrial expansion, urban construction, highway construction, and many other nonfarm activities

• Daily, as many as 8,000 acres of U.S. farmland are converted to nonfarm use

Cont.

7-2

Introduction

• Millions of acres of land are disturbed annually by strip mining for coal and other resources

• As new highways are constructed and old ones are widened, moved, or repaired, millions of miles of road banks are subject to water-caused erosion

7-3

Controlling Nonfarm Erosion

CAUSES

• Construction• Drainage ways drastically

changed• Concrete or asphalt• Runoff problem severe• Sedimentation or gullying • Expensive control practices

7-4

Mechanical Erosion Controls

DIVERSION DITCHES OR BERMS

• Collects the runoff• Typically earth structures• Runoff to an outlet• Ditch is dug out of the ground• Berm is mounded

7-5

Mechanical Erosion Controls

WATERWAYS

• Collect excess soil water• Rock-lined or concrete-lined• Conducted away quickly• Slope is very steep• Steep diversion waterway• Water chute

7-6

Mechanical Erosion Controls

SEDIMENT BASIN

• Like a small pond• Designed to be filled up• Catches excess runoff• Sediment settles• Temporary structures• Used during construction

7-7

Mechanical Erosion Controls

BANK PROTECTION

• Extra efforts to stabilize banks• Seed, mulch or hydroseeding• Concrete or stone walls• Jute matting• Wooden strips placed

across the slope• Chemical binding

7-8

Mechanical Erosion Controls

TERRACING

• Solution on long, steep banks• Breaks into shorter slopes

• Disposal areas• Grassed or lined waterway• Chute• Wooded area• Storm sewer

7-9

Mechanical Erosion Controls

DOWNSTREAM RUNOFF

• Very large construction projects• Large factories• Normal stream flow may be greatly

increased• Flooding• Measures may be needed downstream

7-10

Vegetative Erosion Controls

LAWN

• Most common technique• Nonfarm sites• Seedbed• Sprigging• Plugging• Sodding

7-11

Vegetative Erosion Controls

SOD

• Quick development• Heavy growth of grass• Squares or strips• Living layer• Produced on a sod farm• Soil must be well prepared

7-12

Vegetative Erosion Controls

MULCH

• Holds grass seed in place• Maintains surface moisture• Protects from erosion• Silage-like slurry• Chemical bonding

7-13

Vegetative Erosion Controls

GROUND COVERS

• Low-growing shrubs, • Vines, or other plants • Used much like grass• Combined with mulching• Increase protection

7-14

Vegetative Erosion Controls

TEMPORARY COVER CROPS

• Construction sites• Protect an area temporarily• Construction delays• Many plants can only start at certain times

7-15

Highway Erosion Control

SPECIAL PROBLEMS

• Highway surfaces• Practically waterproof• As level as practical

• Exposed banks• Erosion damage• Sediment

7-16

Strip Mining Operations

PROBLEMS

• Large increase• Appalachia• Very steep slopes• High-velocity water

7-17

Strip Mining Operations

VIRGINIA COAL MINES

• Spoil• Drainage and erosion-control system• Two-year period• Land must be reclaimed• Bond is forfeited with noncompliance

• Government regulations to be followed

7-18

Summary

• The impact of falling raindrops must be absorbed by something other than the soil surface, and the speed of the runoff must be kept under control

• Because almost all construction disturbs and reshapes the land, it exposes the soil to greatly accelerated erosion

Cont.

7-19

Summary

• Mining operations and highway construction present the same or even more extreme problems of erosion

• The best solution to the erosion problem is almost always a combination of both vegetative and mechanical measures

7-20