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Workshop on Modeling Erosion after Fire Ponente: Peter R Robichaud Fecha: 26/09/2012
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Wallow Fire, Arizona USA. June 2011
BAER TOOLS Sede Pirineos
Remote Sensing Imagery Soil Burn Severity Guide Mini Disk Infiltrometer
Erosion/Hydrology Predictions ERMiT, etc VAR Tools Treatment Effectiveness Synthesis
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WEPP Processes
• Rainfall, infiltration, runoff, soil water • Soil detachment, transport, deposition and delivery • Plant growth, evapotranspiration, and senescence • Residue accumulation and decay • Soil consolidation
Erosion Processes • Interrill Erosion – Raindrop splash – Shallow overland Flow
• Rill Erosion – Concentrated flow
• WEPP does not model gullying or landslides
ERMiT: Erosion Risk Management Tool Sede Pirineos
http://forest.moscowfsl.wsu.edu/fswepp/
User Input Sede Pirineos
ERMiT • Event based • Probabilistic • Incorporates Variability
Calculations
Output
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How does ERMiT address variability? – ERMiT does an initial run for 100 years of local climate • probability of occurrence for five largest runoff events
ERMiT Burn Severity Sede Pirineos
High Severity Occurrence Probability
Low Severity
Slope
10%
30%
30%
30%
30%
30%
30%
10%
H
L
H
H
L
L
H
L
H
H
L
H
L
H
L
L
H
H
H
L
H
L
L
L
HHH
LHH
HHL
HLH
LHL
LLH
HLL
LLL
Occurrence Probability
25%
25%
25%
25%
Moderate Severity
Creates a matrix of data: •4 Burn Severity spatial possibilities
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ERMiT. Soil Properties Sede Pirineos
Probability Probability (%) (%)
60
Year 4 1 2 3
50 40 30 20 10 0 Soil Erodibility
Burned Area Assessment Tools Sede Pirineos
CHECK UNITS http://forest.moscowfsl.wsu.edu/fswepp/
ERMiT Custom Climate Option Sede Pirineos
Custom Climate
ERMiT Custom Climate Option Sede Pirineos
1. Select International Town 2. Modify SHOW ME Climate THE CLIMATES
Select Select
ERMiT Custom Climate Option Sede Pirineos
Select
You can edit values in the table. Select: Use These Values Return to Input Screen
Run ERMiT Sede Pirineos
Choose Climate & Soil Vege., Gradient, etc
RUN ERMiT
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Sediment Delivery Exceedance Probability for Gerona, Spain
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100
1st Year
90
2nd Year 3rd Year
80
4th Year 5th Year
70 60 50
Probability (%)
40 30 20 10 0
20
40
60
80
Sediment Delivery (t/ha)
100
120
ERMiT Probabilities Sede Pirineos
To change probability: 1. Enter Percentage 2. Go
ERMiT Probabilities Sede Pirineos
70 % Probability
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BAER Values-at-Risk Economic Justification Tools
VAR Tools Sede Pirineos
• Identifying and Classifying VAR • Mapping VAR-Threat Associations • Probabilities of Occurrence and Effectiveness – ERMiT
• Treatment Costs • VAR Calculation Tool – Benefit-cost analysis • Used where monetary values are readily available
– Implied Minimum Value • Applied to averting loss of non-market resources
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B/C=
Loss of Value ($) * ( Prob (Loss w/o Treatments) –Prob(Loss with Treatment) ) Treatment Cost ($)
B/C = 1.1
28,000 0.9
0.3 16,000
>1 Good!
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Good!
Peak Flow Calculator Sede Pirineos
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Background to the Curve Number (CN) Method
• The SCS developed method to predict peak runoff rates from small agricultural watersheds, mainly in the Midwest
• Method is found in Wildcat and AGWA – A variation is in WEPP Watershed
• Three step approach – Select desired storm (6 or 24-hr) – Estimate runoff depth as a function of watershed condition – Estimate peak flow rate as a function of watershed topography
Estimating Runoff Depth Sede Pirineos
P is precip depth; Q is Runoff Depth; S is storage CN is a bit art, and a bit science, e.g. Greg K’s CN values: Post-fire condition High burn severity with water repellent soils High burn severity without water repellent soils Moderate burn severity with water repellent soils Moderate burn severity without water repellent soils Low burn severity Straw mulch with good coverage Seeding with LEBs1-one year after fire LEBs without water repellent soils
Range of CN values 95 90-91 90 85 Pre-fire CN + 5 60 75 85
Estimating Peak Flow Rate Sede Pirineos
• Peak flow rate is a function of runoff depth, and watershed area, shape, steepness and condition • Most methods estimate a time of concentration (Tc) for the watershed as an indicator of how long it takes a drop of water to flow from the top of the watershed to the outlet – Longer Tc values have lower peak runoff rates
Estimating Peak Flow Rate Sede Pirineos
• Some methods (eg Wildcat) estimate small hydrographs for several precip depths during a storm – Small hydrographs are summed to determine a runoff hydrograph for the entire storm.
• The RMRS Peak Flow calculator estimates peak flow from an NRCS Figure as a function of Tc • Final step is to multiply the peak flow by the area and change to the desired units…
ERMiT Input Screen Sede Pirineos
Choose Climate & Soil Vege., Gradient, etc
RUN ERMiT
Output Sede Pirineos
We are interested in these values
Peak Flow Calculator Sede Pirineos
1. Go back to the website with FS WEPP Models 2. Select Peak Flow Calculator
Peak Flow Calculator Input Sede Pirineos
50.9 90.2 20 300 0.02
Peak Flow Calculator Input Sede Pirineos
84
Peak Flow Calculator Input Sede Pirineos
0.32
Estimated Peak Flow Rate Sede Pirineos
Conclusion: Modeling Tools Sede Pirineos
Erosion Risk Management Tool (ERMiT) Peak Flow Calculator ERMiT Batch Program
Models can be found at: http://forest.moscowfsl.wsu.edu/fswepp/
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ERMiT Batch
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•Microsoft Excel version 97-2003 or newer •A connection to the Internet
http://forest.moscowfsl.wsu.edu/fswepp/ SAVE & CHOOSE LOCATION
CLICK: 2012.08.23 ver
1. Enable Macros (Microsoft Office 2010) Sede Pirineos
Sede Pirineos
If Macros are still disabled… then…
1. Enable Macros (Microsoft Office 2010) Sede Pirineos
1. Enable Macros (Microsoft Office 2010) Sede Pirineos
Close and Reopen the Document
Enable Macros (Microsoft Office 2007) Sede Pirineos
PICK
CLICK OK
Enable Macros (Microsoft Office 2007) Sede Pirineos
1. Office Button Close and Reopen the Document
2. Excel Options
2. Inputs Sede Pirineos
1. Refresh Climates
2. Select Climate and Units
2. Inputs Con’t Sede Pirineos
3. Soil Texture 1. Pick Make sure you start in cell A25 2. To read comments/hints: Move cursor on the red triangle
CLICK SELECT
HINT: Sede Pirineos
TO ENTER THE SAME SOIL TYPE (or anything) FOR ALL YOUR HILLSLOPES: •Move the Cursor to the bottom right corner of the cell until you see black cross. •DOUBLE CLICK. OR Click and Drag down. Let go of the cursor.
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NOTE: Some of the empty column are hidden to show all of the data
Entered Data: Hillslope Code
1 thru 12
Area (hectares)
20
Soil Texture
Sandy Loam
Rock %
5
Slope Length
100/200/300
Vegetation Type
Range
Severity Class
Low/Moderate
Hillslope Gradient
Top
0/0
Middle
50/50
Toe
30/0
3. Run ERMiT Sede Pirineos
1
2
CLICK
3 CLICK
Summary Results – Year 1 Sede Pirineos
Results by Hillslope Code – Year 1 Sede Pirineos
Select Hillslope
CLICK ON THE CELL TO CHANGE PROBABILITY
Select Probability
Treatment
1. Enter Probability 2. Year 3. Calculate Results
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3. Calculate
Treatment Con’t Sede Pirineos
CLICK
Sorting Options
Conclusion: Modeling Tools Sede Pirineos
Erosion Risk Management Tool (ERMiT) Peak Flow Calculator ERMiT Batch Program
Models can be found at: http://forest.moscowfsl.wsu.edu/fswepp/