Demonstration of Online Interfaces for Predicting Soil Erosion in Forests
Webinar Worksheet
Rocky Mountain Research Station
USDA Forest Service
Great Lakes Commission
Chicago District
U.S. Army Corps of Engineers
December, 2011
I.Find details of soil and topography from:
< http://207.180.113.223/from_jim/wepp1.php >
1. Select □ English Units
2. Enter Harrietta, MI in Zoom Box and Click Go .
3. Zoom into the Perkins Creek Watershed 5 miles east of Harrietta with a Shift and
mouse drag. Note road network.
4. Select Build Channel Network and then View Channel Network .
5. Select Set Outlet Point and close message box,
a. Click a couple of cells upstream of a confluence,
b. Build Subcatchments and View Watershed Subcatchments .
c. Note the numbers on each hillslope polygon.
6. Select Review Watershed Summary and note:
a. Area, ______ Acres
b. Longitude and Latitude of outlet, _____ ˚ W and _____ ˚ N; and
c. Dominant soil texture and land use:
Texture: __________ Land Use: _________.
d. Close window .
7. Select Set up WEPP Model :
a. Note nearest climate station is Cadillac, MI;
b. View PRISM Adjustments for this location,
i. Note how much wetter this is than the nearest station
ii. Close Window, and
iii. Select □ Adjust climate using PRISM data.
c. Select:
i. Default soil: Low sev fire sandy loam ;
ii. Default land use: Low Severity Fire ;
iii. Watershed Only and Years to Simulate 1 ;
iv. Soil Loss Tolerance 0.1 ;
v. Run WEPP and View Erosion Maps .
8. Behind + box on right side of map,
a. Deselect □ Representative hillslope soil loss and note
number of hillslope of interest;
b. Select □ Representative hillslope soil loss and note
key to soil loss;
9. Select Summary of Simulation Results to note sediment delivery from each
hillslope and channel segment (should run for 50 years to get these values).
Close window.
10. Select Slope Steepness to get area, length, and distribution of steepness for hill of
interest: _____ Acres; _____ ft length;
Slopes: ____ at top, ____ in middle, ____ at bottom _____ in channel.
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Questions
Go to the Web Site: http://forest.moscowfsl.wsu.edu/fswepp/ .
II.
1. Select the WEPP Road
2. Ponder the interface.
III.
Select the Desired Climate:
1.
2.
3.
4.
Click Custom Climate .
Scroll the Region to Michigan and Click Show Climates .
Select Cadillac and click Modify Climate .
Note the Cadillac Climate (Seems a bit on the dry side),
Enter _____ deg lat and _____ deg long in the upper right corner click the
PRISM box.
5. Note the climate is a bit percent wetter and click Use Prism Values .
6. Note elevation is 100 ft higher,
and Click □ Adjust Temperature for Elevation by Lapse Rate .
7. Name the Climate “ Perkins CK, MI ” and click Use These Values .
8. Click Return to Input Screen .
9. Select Perkins Creek, MI from Climate List.
10. Click Run WEPP to ensure that climate actually works !
11. At the bottom of the output screen, click Return to Input screen .
IV.
WEPP Road Interface
Basic Approach: Model likely current condition and compare to benefits from
gravelling to get rid of ruts and adding a culvert or paving. Assume that the road is
insloped for demonstration, with a single ditch.
A. Most Common surfaces, high traffic and rutted.
1. In Soil Texture Box, select Sandy loam , 20% Rock Content ;
2. For the road design, select Outsloped, rutted ;
for the road surface select Native and
for the traffic level select element High .
3. Specify the topography for a stream crossing:
Element
Road
Fill
Forest
Gradient, %
_____
50
_____
Length, ft
400
4
1
Width, ft
20
4. Specify Create new log for Perkins Creek .
5. Specify 50 years of simulation and click Run WEPP and
Add to log.
B. Getting rid of ruts, change Surface to Graveled and Road design to
Insloped Graveled or Vegetated Ditch and Run WEPP .
Add to log.
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C. Paved Road: Select Paved for road surface and Run WEPP , Add to log.
D. Add Culvert 50 ft before stream crossing: Select High Traffic Road , Graveled
road surface, Increase forest buffer length to 50 ft , and decrease road length to
350 ft ,
Add to log.
E. Don’t forget the last 50 ft: Select High Traffic Road , Graveled road surface,
Decrease buffer length to 1 ft , decrease road length to
50 ft and decrease road gradient to 1 % .
Add to log.
F. Study the log to determine relative benefits from treatments to reduce road
erosion.
G. Copy log and paste into spread sheet for future reference.
Questions
V.
Disturbed WEPP Interface for Fuel Management
Basic Approach: Estimate “background” sediment from undisturbed forest and wildfire;
Compare background to erosion associated with thinning and prescribed fire.
A. Undisturbed Forest Erosion:
1. Select climate Perkins CK, MI and soil Sandy Loam , 20 % Rock.
2. Specify upper and lower treatments to be Mature Forest
3. Specify Slope to be:
_____%
_____%
_____%
_____%
450 ft
50 ft
4. Run WEPP and enter sediment delivery into Table 2 (Columns (1) and (5)).
B. Wildfire before treatment:
1. Change upper treatment to Low severity fire 50 percent cover
and lower treatment to Low severity fire 70 percent cover.
2. Run WEPP and enter sediment delivery into table 2 (column (1)).
C. Calculate “background” sediment budget:
1. Divide the erosion in column (1) by the return interval in column (2) and enter the
results in column (3).
2. Sum up the two average annual values in column (3) to get the background
sediment delivery rate.
D. Estimate the sediment generated by thinning and prescribed fire:
1. For thinning, Upper treatment: select Thin or young forest and set the cover to
85 percent and the Lower treatment to Mature forest leaving the default cover
at 100 percent.
2. Run WEPP and enter the sediment delivery in Table 2, column 5.
3. For prescribed, Upper treatment: select Low severity fire and leave the default
cover to be 85 percent and the Lower treatment as Mature forest with 100
percent cover.
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4. Run WEPP and enter the sediment deliveries in Table 2, column (5).
E. Estimate the sediment generated by wildfire following fuel treatment:
1. Set the upper treatment to Low severity fire , 60 percent cover and
the Lower treatment to Low severity fire , 80 percent cover.
2. Run WEPP and enter the sediment delivery in Table 2, column (5).
F. Calculate “Treated” sediment budget:
1. Divide the erosion in column (5) by the return interval in column (6) and enter the
results in column (7).
2. Sum up the four average annual values in column (7) to get the average annual
treated sediment delivery rate.
3. Discuss the background versus the treated sediment delivery. The extra sediment
from roads, if any, may also need to be considered (low traffic roads become
high?)
Table 2. Summary of Erosion Analysis for Fuel Management
Column:
(1)
(2)
(3)
(4)
(5)
No
Sed
Return
Annual
Treated
Sed
Treatment
Delivery Interval Average
Delivery
(t/a)
(years) (lbs/a/yr)
(t/a)
Forest
Wildfire
(6)
Return
Interval
(years)
Forest
1
Thinning
20
Rx Fire
20
Wildfire
80
Treated sediment delivery rate:
1
50
Background sediment delivery rate:
(7)
Annual
Average
(lbs/a/yr)
Questions
Note: Batch processors are available online for both road segments and hillslopes.
VI.
Combining roads and hillslopes:
1.
For demonstration, assume total managed area is 2000 acres with 5 miles of roads:
Current road sediment: _____ lbs/400 ft x 5 miles =>
_____ tons
Current background sediment _____ lb/a x 2000 acres => _____ tons
Total surface erosion in managed area:
_____ tons
2. Show and discuss benefits and costs of removing some roads and improving other
road segments.
3. Show and discuss benefits and costs or forest management.