Transcript WEPP in the Woods - Washington State University

Useful Tools for Predicting
Erosion from Disturbed
Rangelands: Disturbed WEPP
for Rangelands
The Water Erosion
Prediction Project in
the Forest Service
Objectives of Presentation

To present three interfaces for Predicting
Water Erosion on Rangelands
WEPP ...
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WEPP ...
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Models soil erosion processes
WEPP ...
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Models soil erosion processes
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Was developed cooperatively with
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ARS
NRCS (SCS)
BLM
Forest Service
....
WEPP ...
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Is intended to replace the USLE
– Which predicts Erosion Only
WEPP ...

Is intended to replace the USLE
– Which predicts Erosion Only

WEPP Predicts
– Runoff
– Erosion Rates
– Sediment yield
WEPP Versions
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Hillslope
– Describes a single strip of hillslope
WEPP Versions
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Hillslope
– Describes a single strip of hillslope
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Watershed
– Links hillslopes, channels,
and impoundments
– Very difficult to run
WEPP Versions

Hillslope
– Describes a single strip of hillslope
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Watershed
– Links hillslopes, channels,
and impoundments
– Very difficult to run
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GIS Tool
– GeoWEPP Prototype now available
– Some enthusiasts are developing
custom methods
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Hillslope
WEPP Versions
– Describes a single strip of hillslope
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Watershed
– Links hillslopes, channels,
and impoundments
– Very difficult to run
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GIS Tool
– GeoWEPP Prototype now available
– Some enthusiasts are developing
custom methods
 FS
WEPP Interfaces
– For ease of use on the internet
– ARS has one too
WEPP Processes 1
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Rainfall, infiltration, runoff, soil water
WEPP Processes 2
Rainfall, infiltration, runoff, soil water
 Soil detachment, transport, deposition and
delivery
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WEPP Processes 3
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Rainfall, infiltration, runoff, soil water
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Soil detachment, transport, deposition and
delivery
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Plant growth, evapotranspiration, and
senescence
WEPP Processes 4
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Rainfall, infiltration, runoff, soil water
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Soil detachment, transport, deposition and
delivery
Plant growth, evapotranspiration, and
senescence
 Residue accumulation and decay
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WEPP Processes 5
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Rainfall, infiltration, runoff, soil water
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Soil detachment, transport, deposition and delivery
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Plant growth, evapotranspiration, and senescence
Residue accumulation and decay
 Soil consolidation
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Erosion Processes 1
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Interrill Erosion
– Raindrop splash
– Shallow Overland Flow
Erosion Processes 2
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Interrill Erosion
– Raindrop splash
– Shallow Overland Flow
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Rill Erosion
– Concentrated Channel Flow
– Assumes about 1 m spacing
between rills
» Varied for roads
Erosion Processes 3
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Interrill Erosion
– Raindrop splash
– Shallow Overland Flow
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Rill Erosion
– Concentrated Channel Flow
– Assumes about 1 m spacing between rills
» Varied for roads
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WEPP does NOT model gullying or
landslides
Overland Flow Elements
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Describe variation in soil and vegetation down a hillslope
OFE 1
OFE 2
OFE 3
FSWEPP File Structure
Climate
CLIGEN
& Prism
User
Web
Browser
Interface
FSWEPP
Internet
Model
WEPP
GeoWEPP File Structure
Topographic
Analysis
TOPAZ
GIS
ArcView
Interface
GeoWEPP
DATA
DEM
Digital
Raster
Climate
CLIGEN
(& Prism)
Model
WEPP
Limitations to WEPP

Scale may be too small
– Users frequently want 10 sq mi + watersheds
Example WEPP Application
Fort Carson, Colorado
 Nearest Climate Station: Timpas, CO
 Typical Slope Length: 300 m (1000 ft)
 Steepness: 25%
 Soil: Loam
 Vegetation: Grass/Sage,
about 30% cover
 Observed erosion rates:
2.5 Mg/ha (1 t/acre)
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Predicted Sediment
Delivery (Mg/ha)
Disturbed WEPP Performance
6
5
4
3
2
1
0
Predicted Vs. Observed Disturbed Rangeland Sediment
Delivery
y = 0.9593x + 0.681
R2 = 0.7315
Avg Erosion = 2.5 Mg/ha
0
2
4
Observed Sediment Delivery (Mg/ha)
6
Disturbed WEPP Template
OFE 1
OFE 2
Treatment 1
Treatment 2
Slope 1
Slope 4
ERMiT Template
P(Erosion) = f(P(Climate), P(Soil), P(Distribution))
OFE 1
OFE 2
Top Slope
OFE 3
For forest, chaparral, and rangeland fire applications
Post processing for mitigation evaluation
Toe Slope
GeoWEPP Template
Download (or obtain) a digital elevation
model …
 Select watershed outlet …
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– Up to 2 sq mi for watershed output (“Offsite”)
– No area limit for hillside output (“Onsite”)
Select files developed in WEPP Windows
 Do not try ArcView Functions until all
GeoWEPP runs complete
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Download GeoWEPP Topo Data
Digital Elevation Model
Digital Raster Graphic
From an NRCS Lighthouse Web Site
GeoWEPP defines channels and
hillslopes
Stream Network
Representative Hillslopes
Area = 324 ha
(800 acres)
Using ARS TOPAZ Topographic Model
GeoWEPP Calculates Hillside
Erosion and Sediment Yield
Hillside Erosion
Sediment Yields from Hills
Using WEPP Watershed Version
GeoWEPP Calculates Channel
Sediment Routing
2
Channel
Output
Mg
2
Input
Mg
91
3
45
51
4
16
18
171
4
3
Delivery Ratio 0.6
Avg Erosion
0.5 t/ha
(0.2 t/a)
Conclusions
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WEPP Technology shows considerable
promise for natural resources to aid in sitespecific and small watershed erosion
analysis on rangelands
Questions & Comments?