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Using
Soil Erosion Modeling for Improved Conservation Planning:
A GIS-based
Tutorial
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Interpolation and simulation of terrain development with hedges
1. Digital elevation model, slope and curvature
DEMs and topographic parameters were computed from field measured point
data by the regularized spline with tension (RST) method (s.surf.rst) in GRASS5.0, at 0.4m resolution, displayed at 2x
vertical exaggeration.
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contours for 1993 and 1996 |
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DEM with slope draped as color
for 1993, and |
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1996 |
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DEM with profile curvature for
1993, and |
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1996 |
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Cross-section of DEM for 93
(blue) and DEM for 96(red), 7x vertical exaggeration, blue on top are eroded
areas, red on top are areas with aggregation. |
Dynamics of DEM and slope development on a tilled hill slope with hedges
from 1993 - 1996
movie in mpeg format or
animated gif
2. Simulation experiments
The SIMWE model (Mitas and Mitasova
1998) was used to simulate the impact of hedges under various simplified
conditions. Hedges are 3 cells (1.2m) wide located along a contour line running
through the 3rd site from the bottom of each profile. Red spheres show the measured
elevation in 1996, green spheres show elevation in 1993 at the start of
simulation. Cyan - blue is deposition, yellow-red is erosion.
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Terrain and erosion/deposition pattern development for 7 steady-state events
with uniform rainfall excess 36mm/hr, and Mannings n=0.2(hedge) and n=0.15(field),
with elevation change proportional to predicted erosion/deposition rate.
The model predicts deposition above and within the hedge and erosion below
the hedge. Swales have increased deposition while noses (convex areas)
have increased erosion.
Sequence of images representing terrain and erosion/deposition after 1, 3 and 6 events:
Animation of terrain and erosion/deposition pattern development for
all 7 events
animated gif
Note, that without the smoothing effect of tillage, smaller events,
wind or other phenomena between the rainfall events, the model predicts
development of rills, in spite of the fact that rilling is not explicitly
incorporated into the model - it appears spontaneously. A closer
look at the model is needed to find out whether the method really simulates
(at least approximately) the development of rills, or whether this is
just the effect of the numerical solution of the equations governing overland flow.
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Terrain and erosion/deposition pattern for one steady-state event
with uniform rainfall excess 36mm/hr
and Manning's n for hedge 0.2 and for the field 0.05. The four times higher
Manning's n for hedge (without taking into account higher infiltration)
causes a sharp increase in water depth within the hedge and
consequent erosion ABOVE and below the hedge. In the field experiment,
hay bales were placed every 9m perpendicular to the hedge to prevent water flow along the hedge, so the predicted effect seems to be realistic.
References
Helena Mitasova, Lubos Mitas, University of Illinois at Urbana-Champaign
in cooperation with Seth M. Dabney, USDA-ARS National Sedimentation
Lab, Oxford, MSCopyright © 2000 Helena Mitasova, GMS Laboratory,
University of Illinois at Urbana-Champaign
For requests to use this material or its parts please
contact Helena Mitasova
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Seth M. Dabney et al. 1999
Lanscape Benching from Tillage Erosion Between Grass Hedges, in press
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Mitas, L., Mitasova, H., 1999, Spatial
Interpolation. In: P.Longley, M.F. Goodchild, D.J. Maguire, D.W.Rhind
(Eds.), Geographical Information Systems: Principles, Techniques, Management
and Applications, GeoInformation International, Wiley, 481-492.
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Mitas, L., Mitasova, H., 1998, Distributed erosion modeling for effective erosion
prevention. Water Resources Research Vol. 34, No. 3, pp. 505-516.
Up
Hohenfels Example
Camp Shelby extension
Court Creek Pilot Watershed
Court Creek Erosion Example
Simulation of land use impact on erosion and deposition using SIMWE
Interpolation and simulation of terrain development with hedges
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H. Mitasova, et al., Geographic
Modeling Systems Lab, UIUC
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