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Alan F. HamletEric P. SalathéMatt StumbaughSe-Yeun LeeSeshu Vaddey
• U.S. Army Corps of Engineers• JISAO Climate Impacts Group• Dept. of Civil and Environmental Engineering• University of Washington
Estimates of 21st century flood risk in the Pacific Northwest based on regional scale climate model simulations
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Motivation
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Role of Atmospheric Rivers in Flooding (Nov 7, 2006)
Neiman, PJ, LJ Schick, FM Ralph, M Hughes, GA Wick, 2011: Flooding in Western Washington: The Connection to Atmospheric Rivers, J. of Hydrometeorology, (accepted)
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Effects of Projected Warming and Precipitation Change on 21st Century Flood Risk from Previous Research
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Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic Change, DOI: 10.1007/s10584-010-9848-z
21st Century Climate Impacts for the Pacific Northwest Region
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Seasonal Precipitation Changes for the Pacific Northwest
Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic Change, DOI: 10.1007/s10584-010-9848-z
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Relationship Between Change in Q100 and Winter Temp
http://www.hydro.washington.edu/2860/products/sites/r7climate/study_report/CBCCSP_chap7_extremes_final.pdf
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Improving Flood Risk Projections Using High Resolution Regional
Climate Models
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Regional Climate Modeling at CIG WRF Model (NOAH LSM) 36 to 12 km
ECHAM5 forcing CCSM3 forcing (A1B and A2 scenarios)
HadRM 25 km HadCM3 forcing
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Snohomish River Near Monroe, WA
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Simulated Changes in Storm Characteristics
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Simulated Storm Event on 2030-11-27 ECHAM5 A1B
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Simulated Storm Event on 2056-11-20 ECHAM5 A1B
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Preliminary Results for the ECHAM5 A1B Sceario for the 2050s.
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Chehalis River at PorterD
aily
Pea
k F
low
(cf
s)
Dai
ly P
eak
Flo
w (
cfs)
Date of Peak Flow (1 = Oct 1) Probability of Exceedence
ECHAM5 2050 A1B ECHAM5 2050 A1B
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Sauk River near Sauk
ECHAM5 2050 A1B ECHAM5 2050 A1B
Dai
ly P
eak
Flo
w (
cfs)
Dai
ly P
eak
Flo
w (
cfs)
Date of Peak Flow (1 = Oct 1) Probability of Exceedence
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Relationship Between Change in Q100 and Winter Temp
0
1
2
3
-15 -10 -5 0 5 10
Flo
od R
atio
DJF mean temp (C)
0
1
2
3
-15 -10 -5 0 5 10
Flo
od R
atio
DJF mean temp (C)
RCM based on WRF echam5 A1B:
100 year flood ratio of the 2050s to the 1980s
GCM based on Hybrid delta echam5 A1B:
100 year flood ratio of the 2040s to historic runs
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Conclusions:
• Our initial exploration of changing flood risk in the PNW using statistical downscaling points to increasing flood risk in most areas of the region due to projected regional warming and increases in cool season precipitation.
• Regional climate models offer more physically based assessment tools for understanding the potential changes in nature of extreme storms (such as atmospheric rivers), the timing of flooding, and a potentially improved picture of the spatial variations in changing hydrologic extremes across the region.
• Initial results suggest more extreme storms in the early fall and general increases in flood intensity will accompany global climate change in the PNW. In particular, many sites show shifts towards flooding earlier in the water year due to the combination of changes in snowpack and earlier storms.