Forest Roads

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Forest Roads
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Forest Roads Guidelines

• Build for intended uses
• Products to be hauled
• Type of vehicles
• Seasons of use
• Road width limits
• Grade limits
• Limits on stream crossings

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Forest Roads Guidelines

• Design road for soils
• Use soils map
• Use topographic map and aerial photos to layout
  preliminary route
• Plot proposed route on maps, considering
• Drainage and slope
• SMZs
• Inter alia

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Forest Roads Guidelines

• Check proposed route on the ground
• Flag route
• Adjust for problem areas
• Minimize number and size of stream crossings
• Design adequate stream crossing
• Design adequate water control devices

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Forest Roads Guidelines

• Plan for stable outlets for water control devices
• Plan for adequate right-of-way width
• Revegetate ASAP
• Plan for maintenance

Roadway seeded to hold until next use
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Soils and Slopes

• Problems related to soil and slope combinations
• Wetness

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Soils and Slopes

• Problems related to soil and slope combinations
• Erosion

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Soils and Slopes

• Problems related to soil and slope combinations
• Sloughing (slumping)

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Sandy Soils

• Wetness and sloughing not a problem
• Load carrying capacity greater when wet
• Erosion is major concern

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Clayey Soils

• Holds water well
• Wetness can be problem on flat and poorly drained
  areas
• Road crown and side ditches may be needed
• Keep cut banks at 3 to 1 to prevent slumping

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Loamy Soils

• Usually well drained
• Wetness not a major problem except in bottomlands
• Erosion potential increases with slope

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Water Control Devices

• Road design
• Dont use natural drainages as road ways
• Dont locate roads directly on top of ridges, but
  slightly down from the crest
• Avoid flat areas that can pond water
• Use natural, small cross-drains
• Additional drainage can be obtained using turns
  and curves

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Water Control Devices

• Road construction
• Avoid in-slopping and inside ditches whenever
  possible
• If use inside ditches provide route for water to
  cross over road
• Use water control devices to reduce slope length
• Use curves when possible to shed water from road
• Rolling and broad-based dips are very effective

Out slope
In slope
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Water Control Devices

• Road construction
• Water bars and traffic are not compatible
• Install wing-ditches (runouts) as frequently as
  possible
• Empty water control devices onto stable outlets
• Outlets should be as level and wide as possible

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Water Bars

• Purpose
• Gather and shed water off of surface
• Divert water from inside ditch
• Prevent erosion until vegetation established
• Where suitable
• Little or no traffic
• Abandoned or retired roads and trails
• Firebreaks

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Water Bar
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Water Bars

• Construction guidelines
• Angle across road in down-grade direction
• Tie upper end into inside ditch bank
• Empty onto stable outlets
• Construct mechanically or by hand
• Blade on skidder can be used

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Spacing of Water Bars
Road Grade Distance Between Waterbars
1-2 500-250
3-5 250-125
5-10 125-80
11-15 80-60
16-20 60-40
21-30 40-30
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Broad-Based Dips

• Carefully out-sloped section of road which acts
  as catchment and drainage channel
• Where suitable
• Not for constantly flowing water
• On roads and trails that are being used
• Flat and moderate grades only

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Broad-Based Dips
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Other Types of Water Breaks

• Rubber conveyor belt
• Installed so that only 3 inches of belting
  extends above the road surface to turn water
  aside.

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Rubber Belt Water Bar
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Other Types of Water Breaks

• Open-top wooden box culvert
• To function properly, careful installation and
  regular maintenance are necessary
• Hard to clean out
• Limit to small amounts of runoff

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Wooden Box Culvert
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Cross Drainage Culverts

• Provide cross drainage of inside ditches
• Installation
• Install in low points and small cross drains
• Place at downhill angle
• Seat firmly
• Inlet at same grade as ditch
• Protect outlet from erosion with rip-rap, etc.
• Size to handle flow
• Extend well beyond road fill

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Water Turnouts (Runouts)

• Divert water from diversion device and disperse
  it onto stable surface
• Construction
• Begin with bottm at same level as road ditch
• Angle away from road
• Then, curve it across hill to flatten out grade
• Blend or feather end onto duff
• Never run directly into streams, even intermittent

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Stream Crossings

• Peak runoff flow in cubic feet per second from
  drainage area for a designated level of storm
  event
• Head vertical column of water temporarily
  stacked over culverts entrance. Provides energy
  to force water through pipe
• Spillway flat bottom channel across road to
  downstream side. It handles peak flows exceeding
  culverts capacity without washing out pipe.

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Estimating Stormwater Runoff

• Use map to estimate drainage area
• For standard topo map (124,000, 7.5 minute) 1
  square inch is 90 acres
• Using soils map or experience to determine
  primary soil type
• Determine average slope class for whole drainage
• Use table
• One square mile is 640 acres

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Culvert Size Guidelines (inches)
Sandy Sandy Sandy Loamy Loamy Loamy Clay Clay Clay
Flat Moder. Steep Flat Moder. Steep Flat Moder. Steep
Acres 0-5 5-10 15 0-5 5-15 15 0-5 5-15 15
Drained Dia. Dia. Dia Dia. Dia. Dia. Dia. Dia. Dia.
5 18 18 18 18 18 21 21 21 24
10 18 18 18 21 24 27 27 27 36
20 18 18 18 24 27 36 36 36 42
30 18 18 18 27 30 36 36 42 48
40 18 18 18 27 36 42 42 48
50 18 18 18 30 36 48 48 48
75 18 18 21 36 42
100 21 21 24 36 48
150 21 21 24 42
200 24 24 30 48
250 27 30 30
300 30 36 36
350 30 36 42
400 36 36 42
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Culvert placed too low, plugs easily, hard to
clean out
Culvert placed too high, creates pond on uphill
side, washes out more easily
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• Improperly installed culverts can block fish
  passage
• (A) water velocity too great,
• (B) water in culvert too shallow,
• (C) no resting pool below culvert, and
• (D) jump too high.

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Culvert Placement

• Placement critical for fish migration

Undersized and perched culvert on
McCabe Creek before restoration
Open bottom box culvert on McCabe Creek after
restoration
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Log Culvert
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Other Stream Crossings Fords
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Other Stream Crossings Fords
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Other Stream Crossings Fords

• Use only with low stream banks and solid stream
  bed
• Look for stream sections that can accommodate 50
  ft. level approaches on both sides
• Cross at right angle in straight section of
  stream
• Install defectors to keep road surface runoff
  from entering stream
• Only use if water quality standards allow
  disturbance

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Other Stream Crossings Bridges

• Get engineering help as needed to assure carrying
  capacity
• Use easily removed temporary structure if
  possible
• Get needed permits, if any
• Choose site to allow gradual approaches and
  installation of water deflectors

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Portable Bridges
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Common Mistakes of Road Construction and
Maintenance

• Culverts too small
• Poor route placement
• Wet spots
• SMZs
• Loose soil
• Not enough runouts
• Grades too steep
• Use of fill material taken from SMZ to cover
  culvert
• Blocked culverts
• Improperly maintained road crown

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Common Mistakes of Road Construction and
Maintenance

• Failure to stabilize erosive soils with grass
• Clogged ditches
• Inadequate planning
• Inadequate soil compaction or set-up time
  before heavy use
• Failure by landowner to discuss road uses, plans
  and BMPs with logger or timber buyer