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  The Hyper-Effective Drainage Area Concept…

 S outheast Arizona has recently been impacted by several wildfires.   I n the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.   T he NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.   T ools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable. WHY  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years…

  S outheast Arizona has recently been impacted by several wildfires.  I n the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.   T he NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.   T ools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable. WHY  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years…

  S outheast Arizona has recently been impacted by several wildfires.   I n the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.  T he NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.   T ools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable. WHY  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years…

  S outheast Arizona has recently been impacted by several wildfires.   I n the desert southwest of the United States, wildfire alters the hydrologic response of watersheds greatly increasing the magnitudes and frequency of flash floods.   T he NOAA National Weather Service is tasked with the issuance of flash flood warnings to save life and property.  T ools that allow the weather forecast offices to quickly access the peak flow magnitude and flood potential from burned areas is highly desirable. WHY  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years…

HOW ten watersheds  H ydrologic response within the first two years after the occurrence of wildfire of ten watersheds in Southeast Arizona documented :  F rye Canyon (USGS gage)  D eadman Canyon (private consultant)  M arijilda Canyon (USGS & NWS)  N oon Creek (Schaffner & Reed)  W et Canyon (Schaffner & Reed)  U pper Campo Bonito (USGS)  S abino Creek near Mount Lemmon (Pima Co. gage)  A lder Canyon at Ventana Windmill (Schaffner & Reed)  M adera Canyon (Schaffner & Reed)  R omero Canyon (AZ Geological Survey)  Indirect measurement of peak flows…

Santa Catalina, Santa Rita, and Pinaleno Mountains in Southeast Arizona…

DATA REQUIREMENTS Specifications short-term thunderstorm short-term thunderstorm with a duration approximately equal to or greater than the time of concentration for the burned basin at outlet equal to or less than the 10- year return interval return interval of rainfall equal to or less than the 10- year return interval hyper-effective drainage area storm core to have moved over at least a portion of the hyper-effective drainage area documented flood was “first major flush” since watershed burned mountainous terrain burn occurred in mountainous terrain small total basin size small total basin size (less than 15 square miles) no dams or other hydraulic structures uncontrolled basin (no dams or other hydraulic structures)  Flood occurred… Upper Campo Bonito

SOUTHEAST ARIZONA POST-BURN FLOOD DATABASE FOR TEN BASINS Prepared by Mike Schaffner and William B. Reed WatershedBasin Average Precipitation (inches) Storm Duration (hours) General Storm 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 across0.6< 1-year Deadman Canyon across0.53-year Marijilda Canyon across0.85-year Noon Creek across0.42-year Wet Canyon across0.31-year Upper Campo Bonito stationary0.310-year Sabino Creek near Mount Lemmon 1.251stationary0.62-year Alder Canyon at Ventana Windmill 1.601down to up1.25-year Madera Canyon stationary0.4< 1-year Romero Canyon up to down1.110-year

SOUTHEAST ARIZONA POST-BURN FLOOD DATABASE FOR TEN BASINS Prepared by Mike Schaffner and William B. Reed WatershedBasin Average Precipitation (inches) Storm Duration (hours) General Storm 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 across0.6< 1-year Deadman Canyon across0.53-year Marijilda Canyon across0.85-year Noon Creek across0.42-year Wet Canyon across0.31-year 1490 (approx 250- year flood) 7.2 Upper Campo Bonito stationary0.310-year Sabino Creek near Mount Lemmon 1.251stationary0.62-year Alder Canyon at Ventana Windmill 1.601down to up1.25-year Madera Canyon stationary0.4< 1-year Romero Canyon up to down1.110-year

ADDITIONAL SELECTED BASIN VALUES Prepared by Mike Schaffner and William B. Reed WatershedLocationModified channel relief 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 CreekPinaleno Mountains Deadman CanyonPinaleno Mountains Marijilda CanyonPinaleno Mountains Noon CreekPinaleno Mountains Wet CanyonPinaleno Mountains Upper Campo BonitoSanta Catalina Mountains Sabino Creek near Mount Lemmon Santa Catalina Mountains Alder Canyon at Ventana Windmill Santa Catalina Mountains Madera CanyonSanta Rita Mountains Romero CanyonSanta Catalina Mountains

ADDITIONAL SELECTED BASIN VALUES Prepared by Mike Schaffner and William B. Reed WatershedLocationModified channel relief 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 CreekPinaleno Mountains Deadman CanyonPinaleno Mountains Marijilda CanyonPinaleno Mountains Noon CreekPinaleno Mountains Wet Canyon Pinaleno Mountains Upper Campo BonitoSanta Catalina Mountains Sabino Creek near Mount Lemmon Santa Catalina Mountains Alder Canyon at Ventana Windmill Santa Catalina Mountains Madera CanyonSanta Rita Mountains Romero CanyonSanta Catalina Mountains

1) 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) 2)determine the return period of these rain events, 3) 3)determine the peak flow of the flood event, 4) 4)calculate the pre-burn peak flow for the corresponding return period of the precipitation event, 5) 5)calculate the pre-burn 5-year peak flow, 6)ratio of pre-burn peak flow to post-burn peak flow 1 6)calculate the ratio of pre-burn peak flow to post-burn peak flow 1 and 7) 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 Post-Burn Flows This ratio is calculated by dividing the result of step 3 by the result of step 4 and is basin specific… 1 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 WatershedLocationPre-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 CreekPinaleno Mountains Deadman CanyonPinaleno Mountains Marijilda CanyonPinaleno Mountains Noon CreekPinaleno Mountains [1] [1] Wet CanyonPinaleno Mountains [2] [2] Upper Campo Bonito Santa Catalina Mountains Sabino Creek near Mount Lemmon Santa Catalina Mountains Alder Canyon at Ventana Windmill Santa Catalina Mountains Madera CanyonSanta Rita Mountains Romero CanyonSanta Catalina Mountains [1] [1] Above Crippen and Bue (1977) value of 23,700. [2] [2] Above Crippen and Bue (1977) value of 13,500. These y values are referred to as target values.

PRE-BURN AND POST-BURN 2-YEAR, 5-YEAR, AND 10-YEAR PEAK FLOWS Prepared by William B. Reed WatershedLocationPre-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 CreekPinaleno Mountains Deadman CanyonPinaleno Mountains Marijilda CanyonPinaleno Mountains Noon CreekPinaleno Mountains [1] [1] Wet CanyonPinaleno Mountains (approx 500-year flood) [2] [2] Upper Campo Bonito Santa Catalina Mountains Sabino Creek near Mount Lemmon Santa Catalina Mountains Alder Canyon at Ventana Windmill Santa Catalina Mountains Madera CanyonSanta Rita Mountains Romero CanyonSanta Catalina Mountains [1] [1] Above Crippen and Bue (1977) value of 23,700. [2] [2] Above Crippen and Bue (1977) value of 13,500.

 Post-Burn Response up to 207 times greater than Pre-Burn… Prepared by William B. Reed

MULTIVARIATE RUNOFF INDEX(mvi) MULTIVARIATE RUNOFF INDEX (mvi)   V ariables:   H yper-Effective Drainage Area (determined from burn severity)   A verage Basin Elevation   O bjective Southeast Arizona Specific — Modified Channel Relief Ratio   R eturn Interval of the Forecasted Rainfall Event  Basin and storm properties chosen after several tries… Noon Creek

hyper-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…

modified 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… Marijilda Canyon

   two types of equations   Fixed Flow Return Interval   Rainfall Return Interval a Variable and Flow Return Interval Not Assigned  mvi AlphaPsiBetaPhiLambda

Fixed Flow Return Interval –Post-Burn 2-Year Flood (97%) * –Post-Burn 5-Year Flood (67%) –Post-Burn 5-Year Flood (67%) * –Post-Burn 10-Year Flood (41%) *  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years  Hydrologic recovery to near pre-burn conditions takes 3 to 5 years… Chance of one or more events in 5 years * Chance of one or more events in 5 years

Prepared by William B. Reed  Ten data points (2-year target values)…

 Ten data points (5-year target values)… Prepared by William B. Reed y = x y = x R 2 = Multivariate Runoff Index Envelope Curve Peak Flow (cfs) 2nd year Best Fit Equation R 2 adj = 0.96 Cross Validation Standard Error = 1757 cfs Cross Validation Adjusted Correlation Coefficient = 0.90 Cross Validation R 2 adj = 0.81 predictive equation: peak flow = 1993 times multivariate runoff index An Empirical 5-Year Post-Burn Runoff Equation for Southeast Arizona Watersheds

Prepared by William B. Reed  Ten data points (10-year target values)…

Fixed Flow Return Interval Concerns –Developed by Assuming T-Year of Rainfall was equal to T-Year of Flow –Same Basin Specific Ratio Used for 2-Year, 5-Year, and 10-Year Flow Return Intervals  Not bad assumptions given the properties of the data set  Not bad assumptions given the properties of the data set…

Flow Return Interval Not Assigned Flow Return Interval Not Assigned ( T-Year Equation )  Rainfall Return Interval a Variable…

Prepared by William B. Reed Ten data points where Best Fit Curve is independent of target values…. Envelope Curve Defined to be Above Target Values Assuming T-Year of Flow is Equal to T-Year of Rainfall. ?

Prepared by William B. Reed  40 data points includes 30 target values… Looks better but is it? This Envelope Curve is Equation 10.

Question  Duration of storm equal to or greater than time of concentration… Can T-Year Equation and Return Interval Equations be Unified?

Paradigm Shift –Target Values Evaluated –Results Consistent with Expectations –Modified Values Used  Assuming t-year best fit equation is correct…

= post-burn runoff for the t-year return intervals between 1 and 10 years (cfs) Modified Target Values Envelope Curve  2-year unique target values were increased by 22%,  5-year values were unchanged, and  10-year unique target values were decreased by 38%. Preliminary Results (mvi 6 ) =

Prepared by William B. Reed  34 data points includes 24 modified target values… Preliminary Results This Envelope Curve is Equation 12.

Return interval increasing Preliminary Results

Conclusions T he use of Hyper-Effective Drainage Area Concept has been demonstrated. T he use of Hyper-Effective Drainage Area Concept has been demonstrated. T wo types of equations for Post-Burn Flows have been developed: T 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. T hese equations provide similar results. T hese equations provide similar results. Use of modified target values recommended… Use of modified target values recommended…

Acknowledgments 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 Canyon

Selected References C rippen, J. and C. Bue, Maximum Flood flows in the Conterminous United States. USGS Water Supply Paper R eed, W. and M. Schaffner, 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: R eed, 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. S chaffner, 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 Available online: S chaffner, 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 Available online: T homas, B., et. al., Methods for Estimating Magnitude and Frequency of Floods in the Southwestern United States. USGS Water-Supply Paper Available online:

Thank You. Basin Conditions River Forecasts Water Supply