Uncertainty in Base Flood Elevation

Kate MarneyCE 394

Statistics in Water Resources

Introduction

• HEC Statistical Software Package

• Bulletin 17B analysis• National Academies

Study Conclusion:– Sampling error does not

vary with topography, drainage area, or landscape type

Average

Objective

Gain insight into the sampling variation of extreme water surface elevations in an arid environment.

Colorado River in Marble Canyon (Source: Britannica Online)

Identifying Gaging Stations

HydroExcel

Identifying Gaging Stations

Accessing Data

Peak Gage Height Data

SiteName State County Latitude Longitude Gage NumberRecord Length (years)

Drainage Area (sq. miles)

COLORADO RIVER AT LEES FERRY, AZ AZ Coconino 36.86471176 -111.5882187 09380000 87 111800LITTLE COLORADO RIVER AT WOODRUFF, AZ AZ Navajo 34.7828064 -110.044281 09394500 82 8072PUERCO RIVER NEAR CHAMBERS, AZ AZ Apache 35.18224716 -109.447052 09396100 36 2156CHEVELON FORK BELOW WILDCAT CANYON, NR WINSLOW, AZ Navajo 34.6364212 -110.7142944 09397500 47 271COLORADO RIVER NEAR GRAND CANYON, AZ AZ Coconino 36.10137177 -112.0862808 09402500 86 141600EAGLE CREEK ABOVE PUMPING PLANT, NEAR MORENCI, A AZ Greenlee 33.06450653 -109.4422989 09447000 62 622BONITA CREEK NEAR MORENCI, AZ. AZ Graham 32.955616 -109.531189 09447800 26 302SAN CARLOS RIVER NEAR PERIDOT, AZ. AZ Graham 33.29644775 -110.4514847 09468500 78 1026GILA RIVER BELOW COOLIDGE DAM, AZ. AZ Pinal 33.16950607 -110.5312119 09469500 53 12886ARAVAIPA CREEK NEAR MAMMOTH, AZ. AZ Pinal 32.84367752 -110.6198196 09473000 55 537GILA RIVER AT KELVIN, AZ. AZ Pinal 33.10284042 -110.9765015 09474000 96 18011SANTA CRUZ RIVER NEAR LOCHIEL, AZ AZ Santa Cruz 31.3553791 -110.5895233 09480000 59 82.2BLACK RIVER BLW PUMPING PLANT, NR POINT OF PINES AZ Graham 33.4767189 -109.7639771 09489500 54 560VERDE RIVER NEAR PAULDEN, AZ AZ Yavapai 34.89501953 -112.3429489 09503700 44 2507VERDE RIVER NEAR CLARKDALE, AZ AZ Yavapai 34.85224152 -112.0659943 09504000 42 3503DRY BEAVER CREEK NEAR RIMROCK, AZ AZ Yavapai 34.72863007 -111.7757111 09505350 46 142WEST CLEAR CREEK NEAR CAMP VERDE, AZ AZ Yavapai 34.53863525 -111.6940384 09505800 42 241VERDE R BLW TANGLE CREEK, ABV HORSESHOE DAM, AZ. AZ Yavapai 34.07309341 -111.7162552 09508500 81 5858SYCAMORE CREEK NEAR FORT MCDOWELL, AZ. AZ Maricopa 33.69421005 -111.5418015 09510200 47 164AGUA FRIA RIVER NEAR MAYER, AZ. AZ Yavapai 34.31530762 -112.0640488 09512500 67 585

Average 59.5

Results

Results

Results

09380000 - Stage (ft)

Percent Change Exceedance Return Period (year) Computed Curve

Stage in ft

Confidence Limits Stage in ft

0.05 0.95

0.2 30.863 31.974 34.885 28.014

0.5 27.744 28.472 30.917 25.458

1 25.502 26.004 28.106 23.597

2 23.345 23.677 25.439 21.785

5 20.594 20.763 22.101 19.435

10 18.553 18.646 19.682 17.654

20 16.494 16.534 17.308 15.807

50 13.513 13.513 14.052 12.985

80 11.431 11.413 11.935 10.881

90 10.6 10.571 11.117 10.021

95 10.178 9.978 10.55 9.416

99 9.134 9.072 9.692 8.496

Results

Future Work

• Compute standard error for 100 year event

• Plot standard error against drainage area for each gaging station

Questions?• Sources:– Mapping the Zone: Improving Flood Map Accuracy

(http://www.nap.edu/catalog.php?record_id=12573)– USGS NWIS Website– Bulletin 17B

Salt River in Arizona (Source: greglibby.com)