Transcript Forest Roads - Welcome to Purdue University

Forest Roads
Forest Roads: Guidelines
• Build for intended
uses
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Products to be hauled
Type of vehicles
Seasons of use
Road width limits
Grade limits
Limits on stream
crossings
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
– SMZ’s
– Inter alia
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
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
Soils and Slopes
• Problems related to
soil and slope
combinations
– Wetness
Soils and Slopes
• Problems related to soil and slope
combinations
– Erosion
Soils and Slopes
• Problems related to soil and slope combinations
– Sloughing (slumping)
Sandy Soils
• Wetness and sloughing
not a problem
• Load carrying capacity
greater when wet
• Erosion is major
concern
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
Loamy Soils
• Usually well
drained
– Wetness not a
major problem
except in
bottomlands
– Erosion potential
increases with
slope
Water Control Devices
• Road design
– Don’t use natural drainages
as road ways
– Don’t locate roads directly
on top of ridges, but slightly
down from the crest
– Avoid flat areas that can
pond water
– Use natural, small crossdrains
– Additional drainage can be
obtained using turns and
curves
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
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
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
Water Bar
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
Spacing of Water Bars
Road Grade
%
1-2
Distance Between
Waterbars
500-250
3-5
250-125
5-10
125-80
11-15
80-60
16-20
60-40
21-30
40-30
Broad-Based Dips
• Carefully outsloped 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
Broad-Based Dips
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.
Rubber Belt Water Bar
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
Wooden Box Culvert
Cross Drainage Culverts
• Provide cross drainage of inside ditches
• Installation
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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
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
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
culvert’s entrance. Provides
energy to force water through
pipe
• Spillway – flat bottom channel
across road to downstream
side. It handles peak flows
exceeding culvert’s capacity
without washing out pipe.
Estimating Stormwater Runoff
• Use map to estimate
drainage area
• For standard topo map
(1:24,000, 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
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
Culvert placed
too low, plugs
easily, hard to
clean out
Culvert placed
too high, creates
pond on uphill
side, washes out
more easily
• Improperly installed culverts can block fish
passage:
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(A) water velocity too great,
(B) water in culvert too shallow,
(C) no resting pool below culvert, and
(D) jump too high.
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
Log Culvert
Other Stream Crossings: Fords
Other Stream Crossings: Fords
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
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
Portable Bridges
Common Mistakes of Road Construction
and Maintenance
• Culverts too small
• Poor route placement
– Wet spots
– SMZ’s
– Loose soil
• Not enough runouts
• Grades too steep
• Use of fill material taken from SMZ to cover
culvert
• Blocked culverts
• Improperly maintained road crown
Common Mistakes of Road Construction
and Maintenance
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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 BMP’s with logger or timber buyer