Forest Roads

1
Forest Roads

• Colleen O. Doten
• August 18, 2004

2
Outline

• Forest Roads in the Distributed
  hydrology-soil-vegetation model
• Erosion and Sediment Transport Module
• Implementation
• Output

3
Forest Roads in DHSVM

• Interception of shallow groundwater
• Flows through the road-side ditch network
• Discharges from culvert

4
Hydrologic Impacts of Forest Roads

• Result of a number of characteristics
• Location in hillslope and upslope contributing
  area (user specified)
• Depth of road-side ditches (user specified)
• Road drainage connectivity (DEM resolution)
• Culvert density (user specified)
• Soil properties (i.e., depth, hydraulic
  conductivity) (user specified)

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Hydrologic Impacts of Forest Roads

• Bowling and Lettenmaier(1997) and LaMarche and
  Lettenmaier (1998)
• Deschutes River subbasins road densities from
  3.2 to 5.0 km/km2
• Increase in peak flows
• Average change in peaks over threshold 1.8 to 9

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Hydrologic Impact of Forest Roads
Drier with roads Wetter with roads
Hard and Ware Creeks, WA
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Outline

• Distributed hydrology-soil-vegetation model
• Erosion and Sediment Transport Module
• Implementation
• Output

8
Erosion and Sediment Transport Module
MASS WASTING
Soil Moisture Content
Sediment
Channel Flow
Sediment
DHSVM
CHANNEL ROUTING
Precipitation Leaf Drip Infiltration and
Saturation Excess Runoff
Erosion Deposition
HILLSLOPE EROSION
ROAD EROSION
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Over road Flow

• Runoff generation by infiltration excess is
  determined by DHSVM.
• Runoff is partitioned based on area of the road
  in the grid cell.
• Flow is modeled using an explicit finite
  difference solution of the kinematic wave
  approximation to the Saint-Venant equations.

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Over road Flow Routing

• Flow enters the road-side ditch in the grid cell
  in which it was generated (Wigmosta and Perkins,
  2001)
• Routing takes into account crown

hillslope
road crown
road- side ditch
fillslope
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Detachment

• Sediment becomes available for transport by
• two mechanisms (roads)
• Effects of maintenance and use
• erodibility coefficients
• particle size

raindrop impact
shearing by overland flow
Mechanisms of Soil Particle Detachment
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Soil particle detachment by raindrop impact

• Dr cfkr2
• where
• cf erodibility coefficient
• k reduction factor due to surface water depth
• r rainfall intensity

KINEROS
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Soil detachment by runoff

• Modeled with transport capacity (TC) as a balance
  between erosion and deposition.
• where
• cg CHvs/h
• CH a flow detachment efficiency coefficient
• vs particle settling velocity
• C sediment concentration
• A flow area
• h flow depth

KINEROS
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Sediment Transport

• Sediment available for transport is routed using
  a four-point finite difference solution of the
  two-dimensional conservation of mass.
• Amount transported is limited by the transport
  capacity.

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Four-point finite difference equation
Detachment (rain and overland flow)
Current time step, current pixel concentration
Previous time step, current pixel mass
Previous time step, upstream pixel mass
Current time step, upstream pixel mass
Current time step, current pixel flow rate
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Transport capacity relationship

• KINEROS (Woolhiser) relationship
• Same as Hillslope erosion, except
• is 0.0004 m/s

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Sediment Routing

• Road surface sediment
• Routed according to the crown type.
• Added to the road-sided ditch is routed through
  the network to a culvert.
• Delivery from culvert to stream based on
• proximity
• particle size (Duncan et al., 1987)

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Outline

• Distributed hydrology-soil-vegetation model
• Erosion and Sediment Transport Module
• Implementation
• Output

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Test Catchment Rainy Creek
Existing road network Total Length 46
km Density 1.05 km/km2 Road Surface Area 0.23
km2 No. Culverts 284 Culvert locations stream
crossings (91) road low points (193) Road
Segments 332
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Road Classes
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Road Statistics
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Sediment Module Implementation

• Spatially constant parameters
• road crown 0.02 meters/meter (Road
  Preconstruction Handbook)
• Spatially variable parameters
• Mannings roughness coefficient, n 0.015
  0.02(KINEROS2 model documentation)
• Rainsplash erodibility coefficient 200
  300(Smith et al. 1999)
• Overland flow erodibility coefficient 0.0025
  0.35 (Smith et al. 1999)
• d50 0.1 10 mm (Dietrich et al., 1982)
• Run for a six-year period 10/1/1991 to 9/30/1997

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Outline

• Distributed hydrology-soil-vegetation model
• Erosion and Sediment Transport Module
• Implementation
• Output

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Default Output

• AggregatedSediment.Values
• Road erosion (basin average in m)
• Road erosion delivered to hillslope (basin
  average in m)
• Total overroad inflow (kg)
• MassSediment.Balance
• Road erosion (basin average in m)
• Road erosion delivered to hillslope (basin
  average in m)
• Total overroad inflow (kg)
• Total culvert return sediment flow (kg) 
• Total culvert sediment to channel (kg)
• Total amount of sediment stored in channels (kg)
• Final Sediment Mass Balance
• Basin Average Road Surface Erosion
• Road Surface Erosion (mm) -7.51e-03
• Road Surface Erosion (kg/hectare) -2.02e02
• Road Sediment to Hillslope (mm) 2.12e-03

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Default/Optional Output

• Sed.Road.Flow
• total mass (kg) in the segment
• total outflow concentration (ppm) from the
  segment
• Sed.Road.FlowOnly total outflow concentration
  (ppm) from the segment
• Model Map (binary file) and Graphic Image
  (real-time)
• Road Surface Erosion
• Sum of lateral inflows (hillslope and road
  surface) (ascii file)

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Model Results

• Simulated Rates, kg/ha/yr
• Road surface erosion 17 41 (164 394 kg/km
  road) (3,2477,842 kg/ha of road)
• Range based on minimum (0.0025) and maximum
  (0.035) overland flow erodibility coefficient
• Changes in raindrop erodibility coefficient (100
  2 x 107) had no affect
• Published Rates, kg/ha/yr
• Road surface erosion
• 3,800 to 500,000 kg/km of roadOlympic Peninsula,
  WA(Reid and Dunne, 1984)
• 12,000 to 55,000 kg/ha of road central
  ID(Ketcheson et al., 1999)

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Sensitivity Analysis

• Road erosion increases with decreasing particle
  size (d50 10 mm vs 0.1 mm)
• Road erosion increases with increasing overland
  flow erodibility coefficient (CH 0.0025 vs.
  0.035)
• Road erosion increased with decreasing stream
  power criteria
• Variables with little or no effect
• Cell factor
• Mannings n
• Particle density

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References

• Dietrich, R.V., J.J.T. Dutro, and R.M. Foose,
  1982 AGI Data Sheets for geology in the field,
  laboratory, and office, 2nd ed., American
  Geological Institute, Falls Church, VA.
• Duncan, S.H., R.F. Bilby, J.W. Ward and J.T.
  Heffner, 1987 Transport of Road-Surface Sediment
  Through Ephemeral Stream Channels, Wat. Resour.
  Bull., 23, 113-119.
• Ketcheson, G.L., W.F. Megahan, and J.G. King,
  1999 "R1-R4" and "BOISED" Sediment Production
  Model Tests using Forest Roads in Granitics, J.
  Amer. Water Resour. Assoc., 35, 83-98.
• KINEROS2 model documentation (http//www.tucson.ar
  s.ag.gov/kineros/Docs/DocNav.html)
• Smith, R.E., D.C. Goodrich and C.L. Unkrich,
  1999 Simulation of selected events on the Catsop
  catchment by KINEROS2, A report for the GCTE
  conference on catchment scale erosion models,
  Catena, 37, 457-475.
• Reid, L.M., and T. Dunne, 1984 Sediment
  production from forest road surfaces, Water
  Resour. Res., 29, 1753-1761.
• Wigmosta, M.S. and W.A. Perkins, 2001 Simulating
  the effects of forest roads on watershed
  hydrology, In Land Use and Watersheds Human
  Influence on Hydrology and Geomorphology in Urban
  and Forest Areas, M.S. Wigmosta and S.J. Burgess
  (eds), AGU Water Science and Application, V.2, p.
  127-143.
• Woolhiser, D.A., R.E. Smith and D.C. Goodrich,
  1990 KINEROS, A kinematic runoff and erosion
  model documentation and user manual,
  USDA-Agricultural Research Service, ARS-77, 130
  pp.
• Ziegler, A.D., T.W. Giambelluca, and R.A.
  Sutherland, 2001 Erosion prediction on unpaved
  mountain roads in northern Thailand validation
  of dynamic erodibility modeling using KINEROS2,
  Hydrol. Process., 15, 337-358.

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Culvert Discharges