Post on 08-Jan-2018
description
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