ML20080M136
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Tess Harden - USGS Oregon Water Science Center Jim OConnor - USGS Geology, Mineral, Energy and Geophysics Meredith Carr - Nuclear Regulatory Commission
What is Paleoflood Hydrology
.using geologic evidence to understand flood history
Harden and OConnor, 2017
Chattanooga Tennessee River Gorge
Flood deposit 14C 360+/-30 Local material 14C 2210+/-30 Flood deposit Burrow fill Reworked flood deposit 1917??
Provisional data, do not cite
Identified ~30 sites, fully described 17 Focused on sites were preservation of sediment was most ideal Also targeted a full range of site elevations Radiocarbon dating and optically stimulated luminescence (OSL)
NOH-Tenn 79.795 66.07*
47.725*
29.55*
8.4 0
Barkley-Ohio 30.59 21.05 C
u mb er l
an d
TFH-Tenn 36.51 22.35 2.61285*
E l k
Nolichucky-Tenn 32.2 8.4 Nottely-Ocoee 53.8 Ocoee-Tenn 30.52 12.7066*
SFHolston-52.29 15.005*
Ho l s t
on FNH-Tenn 33.595 12.7885*
2.65333*
BRH-Hiwassee 11.88 1.2 Oc o
ee Above-Cum berland
-919 Cum berland-Tenn
-924.80 Tenn-Mississippi
-940
-963 Oh i o
Holston-LilTenn 652.22 630.12 LilTenn-Clinch 594.845*
568.11*
Clinch-Hiwassee 546.94 530.96*
516.93*
500.75*
Hiwassee-Elk 492.04 483.095*
471.793*
434.6 425.72 406.297*
396.31*
386.85 374.23 363.72 337.352*
309.44 295.059*
T en ne s
se e
Elk-Ohio 278.777*
258.8 239.4 227.8 213.73*
200.897*
192.41*
176.32*
150.902*
140.718*
132.82*
123.87*
115.606*
103.46*
95.1375*
85.7033*
77.34*
68.232*
60.538*
52.468*
44.314*
35.8733*
27.0525*
6.71 T
en n
es se e
16 1718 19 20 20621 22 BaySprings 204 205 207 Cum berland Tennessee Clinch Little Tenn Elk Ocoee Hiwassee Forks of River 49 XS's are not Geo-Referenced (
ef user entered XS o-Ref interpolated XS Non Geo-Ref user entered XS Non Geo-Ref interpolated XS)
Tennessee Valley Authority Naturals model in HEC-RAS shortened to provide sufficient length for boundary conditions.
Calibrated to historical high water marks.
TVA, 1940
8 unique paleofloods in ~4,000 years
Bulletin 17C EMA LP3 distribution Discharge uncertainty and perception thresholds USGS PeakFQ England and others, 2019
Benito et al., (in press)
Perception thresholds (17C; England et al., 2019):
- The stage or flow above which a source would provide information on the flood peak in any given year.
- Reflect the range of flows that would have been measured had they occurred
Scenario 1: Gaged plus historical record (1826-2008), 3 perception thresholds Scenario 2-4: 4 paleofloods (350,1000, 1500, 1650); 5 perception thresholds (variation to 1 paleo perception threshold)
Scenario 5-7: 4 paleofloods (variation in age and magnitude); 5 perception thresholds
4 paleofloods used in the flood frequency analysis.
Age and magnitude was varied in some scenarios to account geochronologic and stratigraphic uncertainty.
Historical: 1826-1873 Gage: 1874-2008 Provisional data, do not cite Missing year
Year Discharge, cfs Provisional data, do not cite Perception threshold varies Perception threshold varies Perception threshold varies Red Flower flood age change A.D. 1000 flood magnitude change Red Flower flood magnitude change
Year Discharge, cfs Best estimate
~4000 year record 4 paleofloods and 5 perception thresholds Provisional data, do not cite
Gaged + historical data Provisional data, do not cite
Best estimate
~4000 year record 4 paleofloods and 5 perception thresholds Provisional data, do not cite
Provisional data, do not cite
Scenario 3: 4 Paleofloods, PT1A-PT5, Best Estimate Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 430000 200 0.005 440000 400000 480000 500 0.002 500000 450000 560000 1,000 0.001 540000 480000 620000 10,000 0.0001 700000 600000 900000 Scenario 1: Gaged and Historical Record Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 370000 340000 450000 200 0.005 390000 350000 490000 500 0.002 430000 370000 560000 1,000 0.001 460000 380000 610000 10,000 0.0001 520000 410000 800000 Scenario 5: 4 Paleofloods (Red Flower A.D. 1050),
PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 440000 200 0.005 440000 400000 480000 500 0.002 490000 450000 560000 1,000 0.001 540300 480000 620000 10,000 0.0001 700900 600000 900000 Scenario 7: 4 Paleofloods (Red Flower flood discharge equal to that of Jeff-n-Steph flood), PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 360000 420000 200 0.005 420000 390000 450000 500 0.002 460000 420000 500000 1,000 0.001 490000 440000 540000 10,000 0.0001 580000 510000 690000 Provisional data, do not cite Best Estimate Paleoflood Scenario Gaged + historical record
Scenario 3: 4 Paleofloods, PT1A-PT5, Best Estimate Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 430000 200 0.005 440000 400000 480000 500 0.002 500000 450000 560000 1,000 0.001 540000 480000 620000 10,000 0.0001 700000 600000 900000 Scenario 1: Gaged and Historical Record Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 370000 340000 450000 200 0.005 390000 350000 490000 500 0.002 430000 370000 560000 1,000 0.001 460000 380000 610000 10,000 0.0001 520000 410000 800000 Scenario 5: 4 Paleofloods (Red Flower A.D. 1050),
PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 440000 200 0.005 440000 400000 480000 500 0.002 490000 450000 560000 1,000 0.001 540300 480000 620000 10,000 0.0001 700900 600000 900000 Scenario 7: 4 Paleofloods (Red Flower flood discharge equal to that of Jeff-n-Steph flood), PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 360000 420000 200 0.005 420000 390000 450000 500 0.002 460000 420000 500000 1,000 0.001 490000 440000 540000 10,000 0.0001 580000 510000 690000 Provisional data, do not cite Best Estimate Paleoflood Scenario Change date of large Red Flower flood
Scenario 3: 4 Paleofloods, PT1A-PT5, Best Estimate Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 430000 200 0.005 440000 400000 480000 500 0.002 500000 450000 560000 1,000 0.001 540000 480000 620000 10,000 0.0001 700000 600000 900000 Scenario 1: Gaged and Historical Record Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 370000 340000 450000 200 0.005 390000 350000 490000 500 0.002 430000 370000 560000 1,000 0.001 460000 380000 610000 10,000 0.0001 520000 410000 800000 Scenario 5: 4 Paleofloods (Red Flower A.D. 1050),
PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 370000 440000 200 0.005 440000 400000 480000 500 0.002 490000 450000 560000 1,000 0.001 540300 480000 620000 10,000 0.0001 700900 600000 900000 Scenario 7: 4 Paleofloods (Red Flower flood discharge equal to that of Jeff-n-Steph flood), PT1A-PT5 Return Period AEP EMA Estimate Confidence Limits Lower Upper 100 0.01 400000 360000 420000 200 0.005 420000 390000 450000 500 0.002 460000 420000 500000 1,000 0.001 490000 440000 540000 10,000 0.0001 580000 510000 690000 Provisional data, do not cite Best Estimate Paleoflood Scenario Change magnitude of large Red Flower flood Gaged plus historical record
Adding 4000 years of paleoflood data reduces uncertainty of the very small AEPs by 22-44%
Adding 4000 years of paleoflood data increases the magnitude of the very small AEPs.
Record length has a strong influence on the curve.
Provisional data, do not cite