Title: Forest Roads
1Forest Roads
2Forest 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
3Forest 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
4Forest 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
5Forest 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
6Soils and Slopes
- Problems related to soil and slope combinations
- Wetness
7Soils and Slopes
- Problems related to soil and slope combinations
- Erosion
8Soils and Slopes
- Problems related to soil and slope combinations
- Sloughing (slumping)
9Sandy Soils
- Wetness and sloughing not a problem
- Load carrying capacity greater when wet
- Erosion is major concern
10Clayey 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
11Loamy Soils
- Usually well drained
- Wetness not a major problem except in bottomlands
- Erosion potential increases with slope
12Water 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
13Water 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
14Water 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
15Water 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
16Water Bar
17Water 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
18Spacing 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
19Broad-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
20Broad-Based Dips
21Other Types of Water Breaks
- Rubber conveyor belt
- Installed so that only 3 inches of belting
extends above the road surface to turn water
aside.
22Rubber Belt Water Bar
23Other 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
24Wooden Box Culvert
25Cross 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
26Water 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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29Stream 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.
30Estimating 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
31Culvert 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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33Culvert 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.
35Culvert Placement
- Placement critical for fish migration
Undersized and perched culvert on
McCabe Creek before restoration
Open bottom box culvert on McCabe Creek after
restoration
36Log Culvert
37Other Stream Crossings Fords
38Other Stream Crossings Fords
39Other 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
40Other 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
41Portable Bridges
42Common 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
43Common 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