Effects of Wildfire Effects of Wildfire in the Mountainous in the Mountainous Terrain of Southeast Terrain of Southeast Arizona Arizona Empirical Formulas to Estimate from 1-Year through 10-Year Peak Discharge from Small Post-Burn Watersheds The Hyper-Effective Drainage Area Concept… The Hyper-Effective Drainage Area Concept…
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Effects of Wildfire in the Mountainous Terrain of Southeast Arizona Empirical Formulas to Estimate from 1-Year through 10-Year Peak Discharge from Small.
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Effects of Wildfire in the Effects of Wildfire in the Mountainous Terrain of Mountainous Terrain of
Southeast ArizonaSoutheast Arizona Empirical Formulas to Estimate from
1-Year through 10-Year Peak Discharge from Small Post-Burn
Watersheds
The Hyper-Effective Drainage Area Concept…The Hyper-Effective Drainage Area Concept…
SSoutheast Arizona has recently been impacted outheast Arizona has recently been impacted by several wildfires. by several wildfires.
In the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.
The NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.
Tools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable.
WHYWHY
Hydrologic recovery to near pre-burn conditions takes 3 to 5 yearsHydrologic recovery to near pre-burn conditions takes 3 to 5 years…
Southeast Arizona has recently been impacted by several wildfires.
IIn the desert southwest of the United States, n the desert southwest of the United States, wildfire alters the hydrologic response of wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and watersheds greatly increasing the magnitudes and frequency of flash floods.frequency of flash floods.
The NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.
Tools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable.
WHYWHY
Hydrologic recovery to near pre-burn conditions takes 3 to 5 yearsHydrologic recovery to near pre-burn conditions takes 3 to 5 years…
Southeast Arizona has recently been impacted by several wildfires.
In the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.
TThe NOAA National Weather Service is tasked he NOAA National Weather Service is tasked with the issuance of flash flood warnings to save with the issuance of flash flood warnings to save life and property. life and property.
Tools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable.
WHYWHY
Hydrologic recovery to near pre-burn conditions takes 3 to 5 yearsHydrologic recovery to near pre-burn conditions takes 3 to 5 years…
Southeast Arizona has recently been impacted by several wildfires.
In the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.
The NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.
TTools that allow the weather forecast offices to ools that allow the weather forecast offices to quickly access the peak flow magnitude and flood quickly access the peak flow magnitude and flood potential from burned areas is highly desirable.potential from burned areas is highly desirable.
WHYWHY
Hydrologic recovery to near pre-burn conditions takes 3 to 5 yearsHydrologic recovery to near pre-burn conditions takes 3 to 5 years…
HOWHOW Hydrologic response within the first two
years after the occurrence of wildfire of ten ten watershedswatersheds in Southeast Arizona documented:
RRomero Canyonomero Canyon (AZ Geological Survey)(AZ Geological Survey)
Indirect measurement of peak flows…Indirect measurement of peak flows…
Santa Catalina, Santa Rita, and Pinaleno Mountains in Southeast Arizona…Santa Catalina, Santa Rita, and Pinaleno Mountains in Southeast Arizona…
DATA REQUIREMENTSDATA REQUIREMENTSSpecificationsSpecifications
short-term thunderstormshort-term thunderstorm with a duration approximately equal to or greater than the time of concentration for the burned basin at outlet
return interval of rainfall equal to or less than the 10-equal to or less than the 10-year return intervalyear return interval
storm core to have moved over at least a portion of the hyper-effective drainage areahyper-effective drainage area
documented flood was “first major flush” since watershed burned
burn occurred in mountainous terrainmountainous terrain
small total basin sizesmall total basin size (less than 15 square miles)
uncontrolled basin (no dams or other hydraulic no dams or other hydraulic structuresstructures)
Flood occurred…Flood occurred…Upper Campo BonitoUpper Campo Bonito
SOUTHEAST ARIZONA POST-BURN FLOOD DATABASE FOR TEN BASINS
Prepared by Mike Schaffner and William B. Reed
Watershed Basin Average Precipitation
(inches)
Storm Duration
(hours)
GeneralStorm
Motion
Time of Concentration
(hours)
Rainfall Return Interval
λ
(t-years)
Peak Flow of Flood
y for t-year
(cfs)
Pre-Burn Peak Flow of Rainfall Return
Interval
(cfs)
Frye Creek 0.40 0.5 across 0.6 < 1-year 1400 18.5
Deadman Canyon 1.00 0.5 across 0.5 3-year 5500 67.2
Marijilda Canyon 1.25 0.7 across 0.8 5-year 8470 313
Noon Creek 0.94 0.4 across 0.4 2-year 2684 19
Wet Canyon 0.8 0.7 across 0.3 1-year 1490 7.2
Upper Campo Bonito 1.51 0.5 stationary 0.3 10-year 1900 586
Romero Canyon 1.60 0.5 up to down 1.1 10-year 9500 1420
ADDITIONAL SELECTED BASIN VALUESPrepared by Mike Schaffner and William B. Reed
Watershed Location Modified channelrelief ratio
β
(ft/ft)
High severity burn + Moderate severity burn
α
(%)
Average basin elevation above mean sea level
Φ
(ft/1000)
Drainage Area
ψ
(sq mi)
Frye Creek Pinaleno Mountains0.19 61 8.1 4.02
Deadman Canyon Pinaleno Mountains0.22 51 7.7 4.78
Marijilda Canyon Pinaleno Mountains0.15 59 7.1 11
Noon Creek Pinaleno Mountains0.24 77 7.7 2.99
Wet Canyon Pinaleno Mountains0.26 44 8.1 1.58
Upper Campo Bonito Santa Catalina Mountains 0.07 80 5.5 1.5
Sabino Creek near Mount Lemmon
Santa Catalina Mountains 0.07 55 8.2 3.4
Alder Canyon at Ventana Windmill
Santa Catalina Mountains 0.08 35 6.1 14
Madera Canyon Santa Rita Mountains0.22 15 7.2 4
Romero Canyon Santa Catalina Mountains 0.12 34 5.7 7.25
ADDITIONAL SELECTED BASIN VALUESPrepared by Mike Schaffner and William B. Reed
Watershed Location Modified channelrelief ratio
β
(ft/ft)
High severity burn + Moderate severity burn
α
(%)
Average basin elevation above mean sea level
Φ
(ft/1000)
Drainage Area
ψ
(sq mi)
Frye Creek Pinaleno Mountains0.19 61 8.1 4.02
Deadman Canyon Pinaleno Mountains0.22 51 7.7 4.78
Marijilda Canyon Pinaleno Mountains0.15 59 7.1 11
Noon Creek Pinaleno Mountains0.24 77 7.7 2.99
Wet CanyonPinalenoMountains
0.26 44 8.1 1.58
Upper Campo Bonito Santa Catalina Mountains 0.07 80 5.5 1.5
Sabino Creek near Mount Lemmon
Santa Catalina Mountains 0.07 55 8.2 3.4
Alder Canyon at Ventana Windmill
Santa Catalina Mountains 0.08 35 6.1 14
Madera Canyon Santa Rita Mountains0.22 15 7.2 4
Romero Canyon Santa Catalina Mountains 0.12 34 5.7 7.25
1) calculate the basin average precipitation for events known to have caused floods from the burned basins (an attempt was made to use the first major flush after a burn) and document storm duration,
2) determine the return period of these rain events,
3) determine the peak flow of the flood event,
4) calculate the pre-burn peak flow for the corresponding return period of the precipitation event,
5) calculate the pre-burn 5-year peak flow,
6) calculate the ratio of pre-burn peak flow to post-burn peak flowratio of pre-burn peak flow to post-burn peak flow11 and
7) multiply the pre-burn 5-year peak flow for a basin (determined in step 5) by the corresponding ratio (determined in step 6).
Steps for Calculating 5-Year Steps for Calculating 5-Year Post-Burn FlowsPost-Burn Flows
1 This ratio is calculated by dividing the result of step 3 by the result of step 4 and is basin specific…This ratio is calculated by dividing the result of step 3 by the result of step 4 and is basin specific…
PRE-BURN AND POST-BURN 2-YEAR, 5-YEAR, AND 10-YEAR PEAK FLOWS
Prepared by William B. Reed
Watershed Location Pre-burn 2-year peak discharge
(cfs)
Post-burn 2-year discharge
y for 2-year
(cfs)
Pre-burn 5-year peak discharge
(cfs)
Post-burn 5-year discharge
y for 5-year
(cfs)
Pre-burn 10-year peak discharge
(cfs)
Post-burn 10-year discharge
y for 10-year
(cfs)
Frye Creek Pinaleno Mountains
26 1968 116 8778 254 19228
Deadman Canyon Pinaleno Mountains
31 2514 137 11213 300 24540
Marijilda Canyon Pinaleno Mountains
70 1897 313 8470 686 18522
Noon Creek Pinaleno Mountains
19 2685 86 12149 188 26564[1]
Wet Canyon Pinaleno Mountains
10.2 2110 45.5 9416 100 20690[2]
Upper Campo Bonito
Santa Catalina Mountains 156 499 376 1219 585 1872
Sabino Creek near Mount Lemmon
Santa Catalina Mountains 119 350 278 818 431 1293
Alder Canyon at Ventana Windmill
Santa Catalina Mountains 523 1308 1260 3103 1990 4975
Hyper-Effective Drainage Area (determined from burn severity)
Average Basin Elevation
Objective Southeast Arizona Specific — Modified Channel Relief Ratio
Return Interval of the Forecasted Rainfall Event
Basin and storm properties chosen after several tries…Basin and storm properties chosen after several tries…
Noon CreekNoon Creek
hyper-effective drainage areahyper-effective drainage area
is the area of the high severity burn plus the area of the moderate severity burn (variable in square miles)
the remaining drainage area is not used in the
calculations
therefore, the results of the post-burn envelope curve and a pre-burn equation should be
compared and the higher result used
If in doubt, compare results with standard equations…If in doubt, compare results with standard equations…
modified channel relief ratiomodified channel relief ratio
is the average slope of the basin along the first order channel measured from 1,250 feet (381 meters) below
the ridge to the basin outlet --- (variable in feet/feet)
Excludes reach without channels ~ Includes reach at outlet…Excludes reach without channels ~ Includes reach at outlet…
Marijilda CanyonMarijilda Canyon
The empirical equations use a multivariate runoff index defined as mvi = dcba )1000( (1)
where mvi = multivariate runoff index = high severity burn + moderate severity burn as a fraction of total watershed (square
miles/square miles); = total drainage area (square miles); = modified channel relief ratio (feet/feet); = average basin elevation above mean sea level (thousands of feet); = recurrence interval of rainfall (t-years); and
a, b, c, and d are respective exponents.
mvi = dcba )1000(
two types of equationstwo types of equations Fixed Flow Return Interval
Rainfall Return Interval a Variable and Flow Return Interval Not Assigned
mvimvi
Alpha Psi Beta Phi Lambda
Each equation has a slightly different multivariate runoff index form: multivariate runoff index for 2-year events (mvi1) =
91.156.136.0)1000( ;
multivariate runoff index for 5-year events (mvi2) =28.1254.0)1000( ;
multivariate runoff index for 10-year events (mvi3) =88.023.265.0)1000( ;
multivariate runoff index for 1 to 10 year events (mvi4) =63.07.276.156.0)1000( ;
alternative multivariate runoff index for 1 to 10 year events (mvi5) =05.122.191.149.0)1000( ;
and modified target values multivariate runoff index (mvi6) =
– Developed by Assuming T-Year of Developed by Assuming T-Year of Rainfall was equal to T-Year of FlowRainfall was equal to T-Year of Flow
– Same Basin Specific Ratio Used for Same Basin Specific Ratio Used for 2-Year, 5-Year, and 10-Year Flow 2-Year, 5-Year, and 10-Year Flow Return IntervalsReturn Intervals
Not bad assumptions given the properties of the data setNot bad assumptions given the properties of the data set…
Flow Return Interval Not Flow Return Interval Not
Assigned Assigned (T-Year Equation)
Rainfall Return Interval a Variable…Rainfall Return Interval a Variable…
Post-Burn Peak Flow
y = 5213.9x1.0002
R2 = 0.9528
y = 19083x1.038
0
5000
10000
15000
20000
25000
30000
35000
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Multivariate Runoff Index
Pea
k F
low
(cf
s)
Envelope Curve
Best Fit Equation
Prepared by William B. Reed
Ten data points where Best Fit Curve is independent of target values….Ten data points where Best Fit Curve is independent of target values….
Envelope Curve Defined to be Envelope Curve Defined to be
Ratios are basin specific but follow essentially the same trend.
Preliminary ResultsPreliminary Results
Ratios for Santa Catalina and Santa Rita Mountains
0
5
10
15
20
25
30
0 2 4 6 8 10 12
Return Interval
Rat
io
Alder
Campo Bonito
Madera
Romero
Sabino
Power (Alder)
Power (Sabino)
Power (Campo Bonito)
Power (Romero)
Power (Madera)
Ratios are basin specific but follow essentially the same trend.
Preliminary ResultsPreliminary Results
ConclusionsConclusions TThe use of Hyper-Effective Drainage Area Concept has been demonstrated.he use of Hyper-Effective Drainage Area Concept has been demonstrated.
TTwo types of equations for Post-Burn Flows have been developed:wo types of equations for Post-Burn Flows have been developed:Fixed Flow Return Interval (2-Year, 5-Year, and 10-Year Equations) Rainfall Return Interval a Variable and Flow Return Interval Not Assigned.
TThese equations provide similar results.hese equations provide similar results.
Use of modified target values recommended…Use of modified target values recommended…
AcknowledgmentsAcknowledgments
• Chris Smith, Dan Evans, and Saeid Tadayon of the U.S. Geological Survey
• Barry Scott of Arizona Division of Emergency Management • Robert Lefevre of U.S. Forest Service
• Ann Youberg of the Arizona Geological Survey
• Mike Schaffner, Ed Clark, Kevin Werner and Erik Pytlak of NOAA National Weather Service
Madera CanyonMadera Canyon
Selected ReferencesSelected References
• Crippen, J. and C. Bue, 1977. Maximum Flood flows in the Conterminous United States. USGS Water Supply Paper 1887.
• Reed, W. and M. Schaffner, 2007. Effects of Wildfire in the Mountainous Terrain of Southeast Arizona: An Empirical Formula to Estimate 5-Year Peak Discharge from Small Post-Burn Watersheds. NOAA Technical Memorandum NWS WR-279. Available online: http://www.wrh.noaa.gov/wrh/techMemos/TM-279.pdf.
• Reed, W. and M. Schaffner, in review. Effects of Wildfire in the Mountainous Terrain of Southeast Arizona: Empirical Formulas to Estimate from 1-Year through 10-Year Peak Discharge from Small Post-Burn Watersheds.
• Schaffner, M. and W. Reed, 2005a. Effects of Wildfire in the Mountainous Terrain of Southeast Arizona: Post-Burn Hydrologic Response of Nine Watersheds. NOAA National Weather Service Western Region Technical Attachment 05-01. Available online: http://www.wrh.noaa.gov/wrh/05TAs/ta0501.pdf.
• Schaffner, M. and W. Reed, 2005b. Evaluation of Post-Burn Hydrologic Recovery of a Small Mountainous Watershed: Upper Campo Bonito Wash in Southern Arizona. NOAA National Weather Service Western Region Technical Attachment 05-06. Available online: http://www.wrh.noaa.gov/wrh/05TAs/ta0506.pdf.
• Thomas, B., et. al., 1997. Methods for Estimating Magnitude and Frequency of Floods in the Southwestern United States. USGS Water-Supply Paper 2433. Available online: http://pubs.er.usgs.gov/pubs/wsp/wsp2433#viewdoc.