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Forest Roads

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Wetness can be problem on flat and poorly drained areas ... Wetness not a major problem except in bottomlands. Erosion potential increases with slope ... – PowerPoint PPT presentation

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Title: Forest Roads


1
Forest Roads
2
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

3
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

4
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

5
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
6
Soils and Slopes
  • Problems related to soil and slope combinations
  • Wetness

7
Soils and Slopes
  • Problems related to soil and slope combinations
  • Erosion

8
Soils and Slopes
  • Problems related to soil and slope combinations
  • Sloughing (slumping)

9
Sandy Soils
  • Wetness and sloughing not a problem
  • Load carrying capacity greater when wet
  • Erosion is major concern

10
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

11
Loamy Soils
  • Usually well drained
  • Wetness not a major problem except in bottomlands
  • Erosion potential increases with slope

12
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

13
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
14
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

15
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

16
Water Bar
17
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

18
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
19
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

20
Broad-Based Dips
21
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.

22
Rubber Belt Water Bar
23
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

24
Wooden Box Culvert
25
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

26
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

27
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28
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29
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.

30
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

31
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
32
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33
Culvert placed too low, plugs easily, hard to
clean out
Culvert placed too high, creates pond on uphill
side, washes out more easily
34
  • 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.

35
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
36
Log Culvert
37
Other Stream Crossings Fords
38
Other Stream Crossings Fords
39
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

40
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

41
Portable Bridges
42
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

43
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
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