1. Development of a Sediment Transport Component for DHSVM
Colleen O. Doten, University of Washington Laura C. Bowling, Purdue University Edwin D. Mauer, Santa Clara University Nathalie Voisin, University of Washington Dennis P. Lettenmaier, University of Washington

2. Outline Motivation Distributed Hydrology-Soil-Vegetation Model (DHSVM)
Sediment Transport Component
Testing and Evaluation
Scenario Analyses

3. Motivation Forest Roads Forest Fire Timber Harvest
Forest Fire
Timber Harvest

4. Distributed Hydrology-Soil-Vegetation Model (DHSVM)
Physically based hydrologic model that simulates the effects of spatially variable
topography
soil
vegetation
Solves energy and water balance at each grid cell (pixel), at each time step
1-D Vertical Water Balance
DHSVM Model Representation
4) The tool kit will include a hydrologic model which will allow them to observe flows, periods of flow, peak and low flow events, and effects of various changes in vegetation cover and extent of disturbance on these outputs. Examples.
Surface/Subsurface Flow
Redistribution to/from
Neighboring Pixels

5. Sediment Transport Component
DHSVM
SURFACE EROSION
OUTPUT Q
Qsed
CHANNEL EROSION & ROUTING
Provides Inputs for all Three Components
MASS WASTING
Watershed Sediment Module
Watershed Sediment Module

6. DHSVM Inputs to Sediment Model
Soil Moisture Content
Channel Flow
Precipitation
Leaf Drip
Infiltration and Saturation Excess Runoff
MASS WASTING
CHANNEL EROSION &
ROUTING
SURFACE EROSION

7. Mass Wasting

8. Dynamic soil saturation predicted by DHSVM
Finer resolution grid (10 m) for failure computation
Icicle Creek, WA
L. Bowling, C. Doten

9. Mass Wasting Module (MWM)
Slope stability is a function of soil moisture, slope, and soil and vegetation characteristics.
Failure is determined by the infinite slope stability model, using a factor of safety (FS)
resisting forces
driving forces
FS =
Slope instability is indicated by a FS < 1.
L. Bowling, C. Doten

10. MWM - Stochastic Nature
Four soil and vegetation characteristics:
soil cohesion,
angle of internal friction,
root cohesion, and
vegetation surcharge
are input as probability distributions.
They can be assigned to one of three distributions:
uniform,
normal or
triangular.
L. Bowling

11. Simulated Probability of Slope Failure
Rainy Creek, WA
November 28, 1995
Storm Event
Probability of failure
L. Bowling

12. MWM - Mass Redistribution
Failure depth is equal to the failed pixel soil depth.
Failed material travels down the slope of steepest descent.
Failed area can increase in response to the initial failure.
Landslide stops at an empirically determined runout distance. The failed volume is evenly distributed among all downslope pixels.
Landslides entering channels system continue as debris flows depending on the junction angle.
L. Bowling

13. Surface Erosion & Routing

14. DHSVM Runoff Generation and Routing
Runoff is produced via:
Saturation excess (pixels 6 and 7)
Infiltration excess based on a user-specified static maximum infiltration capacity (pixel 3)
Runoff is routed to the downslope neighbors one pixel/time step

15. Runoff Generation – Infiltration Excess
Dominant form of runoff generation on unpaved roads and post burn land surfaces
Calculation of maximum infiltration capacity:
The first timestep there is surface water on the pixel, all surface water infiltrates.
If there is surface water in the next timestep, the maximum infiltration capacity is calculated based on the amount previously infiltrated.
N. Voisin

16. Runoff Routing
Pixel to pixel overland flow routed using an explicit finite difference solution of the kinematic wave approximation to the Saint-Venant equations
Manning’s equation is used to solve for flow area in terms of discharge
Per DHSVM timestep, a new solution sub-timestep is calculated satisfying the Courant condition, which is necessary for solution stability.
L. Bowling

17. Mechanisms of Soil Particle Detachment
Surface Erosion
Transportable sediment is the sum of particles detached by three mechanisms
Erosion is limited by overland flow transport capacity
raindrop
impact
leaf drip
impact
shearing by overland flow
Mechanisms of Soil Particle Detachment
L. Bowling, N. Voisin

18. Hillslope Sediment Routing
Sediment is routed using a four-point finite difference solution of the two-dimensional conservation of mass equation.
If the pixel contains a channel (including road side ditches), all sediment and water enters the channel segment.
sediment and water
L. Bowling

19. Forest Road Erosion
Transportable sediment consists of particles detached by two mechanisms
Overland flow will be infiltration excess generated.
Routing to include road crown type
insloped
outsloped
crowned
surface erosion
raindrop impact
shearing by
overland flow
C. Doten

20. Channel Erosion & Routing
envben.html

21. Channel Erosion & Routing
Sediment Supply
channel sediment storage from the MWM
lateral inflow from hillslope and roads
upstream channel segment
Sediment particles
have a constant lognormally distributed grain size which is a function of the user-specified median grain size diameter (d50) and d90
are binned into a user-specified number of grain size classes
E. Maurer

22. Channel Erosion & Routing
Sediment is routed using a four-point finite difference solution of the two-dimensional conservation of mass equation.
Instantaneous upstream and downstream flow rates are used in the routing.
Transport depends on
available sediment in each grain size class, and
capacity of flow for each grain size calculated using Bagnold’s approach for total sediment load.
E. Maurer

23. Testing and Evaluation

24. Testing and Evaluation
Mass wasting
Land slide mapping derived from aerial photography
Surface erosion
Observed local and regional land and road surface erosion rates
Run model in location where road data are available
Channel routing
Observed stream sediment concentrations
C. Doten

25. Scenarios Analyses I: Forest Roads
Road Proximity to Streams
Road Location in the Hillslope & Hillslope Curvature
Coffee Creek, British Columbia
C. Doten

26. Scenarios Analyses II: Timber Harvest and Forest Fire
Enhanced Transport Capacity
Decrease in annual evaporation
Increased snow accumulation
Enhanced snow melt
Greater radiation exposure
Increased turbulent energy transfer
Enhanced Sediment Supply
Mass wasting (landslides)
Decreased root strength
Enhanced soil moisture
Surface erosion
C. Doten

27. Questions/Comments

28. Data Input Needed for Sediment Model
Smaller resolution (10m) DEM
Debris Flow Material d50 and d90
Soils: Bulk Density, Saturated Density, Manning n, K index, d50, distributions (mean, stand deviation, minimum value, maximum value) of Cohesion and Angle of Internal Friction
Vegetation: Vegetation Surcharge distribution (minimum value and maximum value) and Root Cohesion distribution (mode, minimum value and maximum value)

29. DHSVM Channel Routing
Flow is routed using a cascade of linear reservoirs.
Each channel segment is treated as reservoir of constant width. Discharge is linearly related to storage. This implies a constant flow velocity.
Storage at the next timestep can be calculated knowing the inflow and velocity (determined using Manning’s equation.)
The average outflow from a reach is obtained through a mass balance.

30. References
Bagnold, R.A., 1966, An approach of sediment transport model from general physics. US Geol. Survey Prof. Paper 422-J.
Benda, L. and T. Dunne, 1997, Stochastic forcing of sediment supply to channel networks from landsliding and debris flow, Wat. Resour. Res, 33 (12),
Beven, K.J. and M.J. Kirkby, 1979, A physically based, variable contributing area model of basin hydrology, Hydrol Sci Bull, 24,
Burton, A. and J.C. Bathurst, 1998, Physically based modeling of shallow landslide sediment yield at a catchment scale, Environmental Geology, 35 (2-3).
Chow V.T., D.R. Maidment, L.W.Mays 1988: Applied Hydrology. McGraw-Hill Book Company pp572.
Epema G.F., H. Th. Riezebos 1983: Fall Velocity of waterdrops at different heights as a factor influencing erosivity of simulated rain. Rainfall simulation, Runoff and Soil Erosion. Catena suppl. 4, Braunschweig. Jan de Ploey (Ed).
Everaert, W., 1991, Empirical relations for the sediment transport capacity of interill flow, Earth Surface Processes and Landforms, 16,
Exner, F. M., 1925, Über die wechselwirkung zwischen wasser und geschiebe in flüssen, Sitzungber. Acad. Wissenscaften Wien Math. Naturwiss. Abt. 2a, 134, 165–180.
Graf, W., 1971, Hydraulics of Sediment Transport, McGraw-Hill, NY, NY, pp
Grayson R.B., Blöschl G. and I.D. Moore : Distributed parameter hydrologic modeling using vector elevation data: THALES and TAPES-C. Chapter 19 in: Computer Models of Watershed Hydrology, Water Resources Publication, Highland Ranch, Colorado. p
Hammond, C., D. Hall, S. Miller and P. Swetik, 1992, Level I Stability Analysis (LISA) Documentation for version 2.0, USDA Intermoutain Research Station, General Technical Report INT-285.

31. References (con’t)
Komura, W., 1961, Bulk properties of river sediments and its application to sediment hydraulics, Proc. Jap. Nat. Cong. For Appl. Mech.
Morgan, R.P.C., J.N. Qinton, R.E. Smith, G. Govers, J.W.A. Poesen, K. Auerswald, G. Chisci, D. Torri and M.E. Styczen, 1998, The European soil erosion model (EUROSEM): a dynamic approach for predicting sediment transport from fields and small catchments, Earth Surface Processes and Landforms, 23,
Rubey, W.W., 1933, Settling velocities of gravels, sands, and silt particles, Am. Journal of Science, 5th Series, 25 (148),
Shields, A., 1936, Application of similarity principles and turbulence research to bedload movement. Hydrodynamic Lab. Rep. 167, California Institute of Technology, Pasadena, Calif.
Smith R.E. and J.Y. Parlange 1978: A parameter-efficient hydrologic infiltration model. Wat. Resour. Res. 14(3),
Smith R.E., D.C. Goodrich, D.A. Woolhiser, and C.L. Unkrich 1995: KINEROS – a kinematic runoff and erosion model. Chapter 20 in: Computer Models of Watershed Hydrology, Water Resources Publication, Highland Ranch, Colorado. p
Sturm, T., 2001, Open Channel Hydraulics, McGraw-Hill, NY, NY, pp
Wicks, J.M. and J.C. Bathurst, 1996, SHESED: a physically based, distributed erosion and sediment yield component for the SHE hydrological modeling system, Journal of Hydrology, 175,
Wigmosta, M.S., and D.P. Lettenmaier, 1999, A Comparison of Simplified Methods for Routing Topographically-Driven Subsurface Flow, Wat. Resour. Res., 35,
Wolohiser, 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.