Soil and Hydrology
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Transcript of Soil and Hydrology
Careful Logging – Partial Cuts
Soil and Hydrology
Concerns Significance What are the Standards? How am I assessed? BMP’s
With support from Forest Research Partnership (Canadian Ecology Centre, Tembec, MNR, CFS) and MTCU
Al Corlett, R.P.F., Forestry Consultant
Careful Logging – Partial Cuts
Soil and Hydrology
Erosion
Rutting
Careful Logging – Partial Cuts
Soil and HydrologyAquatic ValuesSoil Compaction
Careful Logging – Partial Cuts
Soil and Hydrology
Careful Logging – Partial Cuts
Concerns –compaction
heavy equipment at wrong time or place, leading to—
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Careful Logging – Partial Cuts
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Compaction H2O & nutrients can’t
move thru soil as easilyMore surface run-off,
especially if ruttedIncreased moisture
retention – longer to dry
Careful Logging – Partial Cuts
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Compaction soil stays cool longer in the springtime,
shortened growing season and delaying silviculture
Careful Logging – Partial Cuts
Concerns –
compaction reduced growth
- even for light traffic
increased dieback
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Careful Logging – Partial Cuts
Soil and Hydrology
Compaction – influenced by: Texture, ground pressure / vibration, but
most important – moisture contentMost severe, medium to fine textured
soils, especially during wet periods greatest at 60-100% of soils’ water
holding capacity Consequences – lowland sites
Careful Logging – Partial Cuts
Soil and Hydrology
Compaction – influenced by:
# of passes – the first few count!After average 2.5
trips, densities within 10% of the max
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Concerns – effects can last a long time
Soil and Hydrology
32 years: 25% of area still heavily compacted (> 1.2 gm/cc)
(Wert, Thomas 1981)
Up to 18 years(Hatchell & Ralston 1971)
40 years on severely compacted areas
(Perry 1964)
Careful Logging – Partial Cuts
Concerns: Erosion movement of soil particles by wind, water,
gravity
Higher risk: steep or long slopes, unstable road cut/fill sands and silts, shallow soil over bedrock,
water crossings
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Careful Logging – Partial Cuts
Soil and Hydrology
Concerns: Erosionsoil movementsedimentation into fish habitat
Careful Logging – Partial Cuts
Concerns: Erosion smothering of root systems, reduced growth rate mortality
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Careful Logging – Partial Cuts
Soil and Hydrology
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Concern: Rutting wet soils –very prone to rutting/compaction fine textured soils more susceptible than
coarse textured mineral soils. but very fine sands and fine sands may be
susceptible when wet. soils with lots of coarse fragments (e.g.,
stony tills or outwash) are less prone
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Concern: Ruttingespecially bad in the spring and fall when soils are saturated
making re-use of trails difficult – more trails needed next time
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Where are the issues? steep slopes rocky ridges long slopes complex terrain,
water courses treed lowlands
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Risk of damage:•reduced when soil frozen•Increased risk – spring snowmelt, above normal rainfall
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Careful Logging – Partial Cuts
Standards: Rutting standards / BMP’s vary
by district, but under development
evidence – 20cm leads to major, long-term, localized damage.
how much total coverage is acceptable?
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Standards: Rutting Caution: re-using
severely rutted old trails – may put you out of compliance before you even start!
If productivity issue –
re-use If hydrological – re-locate
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Careful Logging – Partial Cuts
BMP’s: Planning – all stages set clear objectives related to forest health regulate the timing of harvest according to
season / site condition (switch to winter harvest if a lot of wetland in the block)
good trail design and planning before the cut
have contingency areas
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Careful Logging – Partial Cuts
BMP’s: Landings use maps, field
information to locate landings
use existing landings (and trails) if appropriate
non-productive sites
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BMP’s: Landings don’t bulldoze (cut
woody veg at ground level)
surface with chips / stone, aggregate if it will stabilize surface
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BMP’s: Landings
To reduce compacted area –
keep as small as possible
pile material as high as safety permits
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BMP’s: Landings gently sloping
(less than 8%, but not flat)
outside AOC’s
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BMP’s: Landings locate so skidding
traffic doesn’t cross natural drainage
locate so water won’t flow in or out where roads or trails enter
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BMP’s: Landings locate to promote
skidding & forwarding down-hill
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BMP’s: Trail Management Minimize sections where water may
be difficult to drain or divert. grades >10%, long unbroken grades, long flat stretches, stretches that are straight up or
downhill that still require ditches
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BMP’s: Trail Management stay out of AOCs, wet areas,
floodplains, outcrops, gullies, sensitive areas (watercourses, seasonal ponds, seeps, poorly drained areas)
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Careful Logging – Partial Cuts
BMP’s: Trail Management stick to coarser soils (sandy or higher
coarse fragments / gravelly), avoid silts and clays
run trails parallel to contours, run upslope trails along ridge crest
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Careful Logging – Partial Cuts
BMP’s: Trail Management avoid locating skid trails on moderate to
steep slopes (it is the gradient of the trail that is critical, not the hillside slope)
winch wood off areas with slopes >30% reach onto slopes with feller/buncher,
place piles at top or bottom of slope
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BMP’s: Trail Management forwarding downhill is preferred (downhill
= favourable grade, uphill = adverse grade recommended grades for primary trails:
<10% adverse (up to 20% OK for short adverse pitches. E.G. 100-200 feet uphill, if straight and level before pitch) – use a clinometer
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BMP’s: Trail Management pre-plan (walk the block
1st to locate wetlands & other sensitive sites)
orient trails away from wetlands, toward dry ground
place tops in wet areas
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BMP’s: Trail Management during dry periods,
operate on low-lying areas with sufficient ground strength first
move to better drained sites when it gets wet
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BMP’s: Trail Management when possible, reach
into wet areas to fell, and
pile bunches on dry ground for easy access by forwarder
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BMP’s: Trail Management in winter, prepare roads
and trails ahead of time so that they are frozen
work wetter areas early in the day while still cold
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Note: 7.5 cm. soil frost to support small equipment, 15 cm. for large
Careful Logging – Partial Cuts
BMP’s: Trail ManagementRisk of unfrozen soils – little frost before snowfall soils are dry temperatures above
freezing lower slopes, wetter
sites
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BMP’s: Trail Management Postpone logging if soil
at 30cm depth will hold a cast
too late if water can be squeezed from a handful of soil, if ruts deep, or if water seeps into ruts
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BMP’s: Trail Management
where roads / trails must be located across contours, use runoff ditches to reduce velocity and magnitude of runoff
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BMP’s: Trail Management drop load, winch across
trouble spots reduce weight of
forwarder forwarders – back-up trail
on short runs rather than having to turn around in the bush
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BMP’s: Trail Management stabilizing exposed soil
wood chips, waste wood, bark mulch lasts several seasons, 2-6” depth,
slopes less than 4:1 (not in areas of concentrated water flow)
gravel low slope, little concentrated flow
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BMP’s: Trail Management stabilizing exposed soil
hay or straw mulchone or two seasons, 2
bales for 30’X30’ areaon steep slopes,
anchor with netting or twine
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BMP’s: Trail Management
stabilizing exposed soil hay or straw mulch
trench 10cm deep, width of bale,
Sloped up 10 cmabove original
ground level
Stake
Hay Bales
TwineFlow
Embed in 10cm deep trench
45cm mindepth intoground
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BMP’s: Trail Management
stabilizing exposed soil single row – no
gaps, backfill on uphill
side
Sloped up 10 cmabove original
ground level
Stake
Hay Bales
TwineFlow
Embed in 10cm deep trench
45cm mindepth intoground
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BMP’s: Trail Management
stabilizing exposed soil vegetation
permanently stabilize disturbed areas
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BMP’s: Trail Management
stabilizing exposed soil vegetation
best on slopes less than 4:1
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BMP’s: Trail Management
stabilizing exposed soil vegetation
rake, grade, remove debris, smooth site
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BMP’s: Trail Management
stabilizing exposed soil vegetation
apply seed spring, fall or after rain
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BMP’s: Trail Management
stabilizing exposed soil vegetation
mulch on dry or erodible soils or if seeded in summer
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BMP’s: Trail Management
stabilizing exposed soil vegetation
no vehicles until well established
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BMP’s: Trail Management stabilizing exposed soil
water bars installed to move water off trail (before
it reaches an AOC)
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BMP’s: Trail Management
stabilizing exposed soil water bars
at least 6-12” deep, 6-12” high, 20-30o to the trails, cross drainage grade of 2%
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BMP’s: Trail Management
Recommended Spacing of Water Bars
% Grade Distance between Water Bars (m)
5 3810 2420 1430 1140 9
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