PROJECT PREPARATION Surface Drainage Module

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PROJECT PREPARATIONSurface Drainage Module

• Specifying Surface Drainage Structures to Solve
  Problem Areas on Trails

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Objective

• Objective of this topic is to educate those
  preparing projects on
• The importance of managing water on or within the
  trail tread
• Being able to identify problems
• Prescribing efficient solutions

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Fundamentals of Surface Subsurface Water Issues

• Surface Water Issues
• Sheet Runoff
• Concentrated within Channels

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Water Issues (cont.)

• Soil Types
• Litter

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Standing water held in trail Causes accelerated
tread failure/erosion
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Water retained on trail tends to widen trail and
promotes by-passes
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Major tread erosion from no cross drainage near
a main water source like a stream crossing or
lake outlet
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Unchecked Surface water
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Failed waterbar with rutting from mountain bike
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Trail widening due to persistent water
retention and mud
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Surface Drainage Structures

• Waterbars
• Open Top Drains
• Drain Dips
• Culverts
• Check dams
• Outsloping
• Ditches
• Berms

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WATERBARS
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922-1 Rock Waterbar

• Angle is critical
• Spillways are critical on erosive soils
• Keying into hillside
• Burial depth important

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922-2 Log Waterbar

• Design basics
• Material options

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922-3 Belted Waterbar

• Design basics
• Material options

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Rock and Log Waterbars

• Intended Uses
• Recommended
• Stock
• Hikers
• Not Recommended
• Motorized (use drain dips or belted)
• Mountain Bikes (use drain dips)

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Rock and Log Waterbars

• Limitations
• Rock Waterbars
• Availability of adequate rock
• Sandy soils
• Log Waterbars
• Availability of local native sources
• Treated sensitivities within wilderness

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Rock and Log Waterbars

• Costs
• Rock Waterbars
• Availability of adequate rock
• Could last forever
• Log Waterbars
• Availability of local native sources
• Native lasts only 8-12 years, depending on
  species and local moisture
• Treated could last 30 50 years
• Maintenance

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Log Waterbar new, good, rock anchors
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Log Waterbar 2-track, well constructed, rebar
anchors
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Log Waterbar Extra wide trail, appears to be
working
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Log Waterbar Native-log w/bark, Wood stakes
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Log Waterbar new installation, appears to be at
90 degrees
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Log Waterbar trail around end of waterbar
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Log Waterbar Sharp bend in trail, sometimes good
location
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Log Waterbar outlet blocked by log
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Log Waterbar waterbar too log, shotguned
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Rock Waterbar good example
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Rock Waterbar Good example
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Rock Waterbar large single rock, need to
watch with stock,
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Belted Waterbar during installation, no wood
frames
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Belted Waterbar after installation
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Belted Waterbar installed on ATV trail
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DRAIN DIPS
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912-4 Drain Dips

• Design basics
• For new construction

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912-4 Drain Dips

• Design basics
• For reconstruction

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Drain Dips

• Intended Uses
• Recommended
• Stock
• Hikers
• Motorized (use drain dips or belted)
• Mountain Bikes (use drain dips)

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Drain Dips

• Limitations
• Difficult to install on reconstruction of steep
  grades

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Drain Dips

• Costs
• Same as for tread construction
• Lasts as long as the tread
• Maintenance
• Easy to maintain

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Natural grade breaks
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CULVERTS
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921-1 Culvert w/ Headwalls

• Plastic or metal, sensitive to where placed
• Need to size to stream hydraulics
• Size of cap rocks critical
• Burial depth important
• Fish Passage may be a requirement

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921-2 Culvert w/o Headwalls

• Stream needs to stabile without a lot of scour
  potential
• Retainers critical to retain tread

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921-3 Rock Culvert

• Need to have adequate source of stone
• Side rocks need to be buried to resist scour
• Soil coverage with retainers

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921-4c Box Culvert

• Plastic or metal, sensitive to where placed
• Need to size to stream hydraulics
• Size of cap rocks critical
• Burial depth important
• Fish Passage may be a requirement

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Culverts

• Intended Uses
• Recommended
• Stock
• Hikers
• Motorized (use drain dips or belted)
• Mountain Bikes (use drain dips)

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Culverts

• Limitations
• Depth and Size
• Plastic or Metal, advantages/disadvantages
• for Setting and Transport
• Plastic does not handle wildfire well

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Culverts

• Costs
• Increase cost of metal culverts
• Maintenance
• Catch basin and outlet must be kept functional
• Pipe must be kept cleaned out to prevent plugging

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Culvert w/ Headwall Squashed metal pipe, with
rock retainers May be alittle small relative to
stream width
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Culvert w/ Headwall round plastic pipe with log
retainers to contain tread materials
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Culvert w/ Headwall Twin round pipes for added
capacity without height Need to ensure adequate
compaction between
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Culvert Maintenance needed
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Culvert Burial depth issue, Maintenance required
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Log Culvert Good example, rustic, tough to get
capacity, tough to clean
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Rock Culvert Tough to get capacity, but rustic
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CHECK DAMS
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915-2 Check Dams

• Wide chose of materials
• Width to trails critical
• Pinning/burial important
• Soil backfill/ compaction to resist bird-baths

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Check Dams

• Intended Uses
• Recommended
• Stock
• Hikers
• Not Recommended
• Motorized (use drain dips or belted)
• Mountain Bikes (use drain dips)

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Check Dams

• Limitations
• Difficult to properly install
• Require future maintenance and monitoring

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Check Dams

• Costs
• Relatively inexpensive to install
• Maintenance
• Requires future maintenance and monitoring

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Check Dams Used in series as part of old tread
restoration
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Check Dams Series of rocks, might be narrow -
notice use outside of established tread
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OUTSLOPING
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Outsloping

• Build in during construction, reconstruction, or
  maintenance
• Preferred on trail classes 1-3
• Harder to maintain on high-class, high-use trails
• Use in combination with cross drains,
  particularly in high risk situations, such as
  below side channels

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Outsloping
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DITCHES
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Ditches

• Start with substantial size, allows to grow in
  and minimizes future maintainace
• Control gradient
• Provide adequate daylighting
• Depth depends on local conditions

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Ditches (cont)

• Use to lower ground water or intercept overland
  flow
• Commonly used in combination with other
  structures such as turnpike
• Relieve water from ditch frequently
• Averages 4 per lineal foot
• Wide and deep ditches last much longer without
  maintenance

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Side Ditches Side ditching to intercept ground
and surface waters
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Leadoff Ditch Drains side ditch, clear well
away from trail to minimize maintenance
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BERMS
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Berms

• Rarely constructed, develop over time due to
  tread erosion, movement
• Remove when not near stream channel, at minimum,
  open frequent holes
• When next to streams, leave berms until water
  from tread can be removed with filtration zone
• Can tend to keep stock within tread and off
  outside edge

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Berms Small berm developing on right, ok for now
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Berms Large berm with substantial Vegetation on
right
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Berm w/ Rock Barrier
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End Surface Drainage