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ClimateChange,HeavyRains,and
FloodinginKingCounty
ResearchTeamGuillaume Mauger, UW Climate Impacts GroupSe-Yeun Lee, UW Climate Impacts GroupJason Won, UW Climate Impacts GroupKatherine Hegewisch, U. Idaho Department of GeographyCary Lynch, Connecticut Department of Energy & EnvironmentRaquel Lorente Plazas, Univ. of Murcia, SpainYolande Serra, UW JISAOEric P. Salathé Jr., UW Bothell
ResearchTeamDepartmentofNaturalResourcesandParksDirector’sOffice
LaraWhitelyBinder
WaterandLandResourcesDivisionRiverandFloodplainManagementSectionKyleComanorFredLottBrianMurrayLorin ReineltJeanneStypula
WaterandLandResourcesDivisionScienceandTechnicalSupportSection
CurtisDeGasperi (ProjectManager)JimSimmonds
Historical
Low Emissions (RCP 4.5)
High Emissions (RCP 8.5)
1950 1975 2000 2025 2050 2075 2100
0°F
5°F
10°F
15°F
0°F
5°F
10°F
15°F
Year
Temperature Difference(Relative to 1950−1999 average)
Year
Precipitation Change(Relative to 1950−1999 average)
1950 1975 2000 2025 2050 2075 2100
−40%
−20%
0%
20%
40%
60%
−40%
−20%
0%
20%
40%
60%
Substantial Warming, Variable Rainfall
Wheredotheseprojectionscomefrom?
https://serc.carleton.edu/eet/index.html
Warner, Mass, Salathé, J Hydromet, 2014
Global models project an increase in heavy rains
Heaviest rain events are projected to become +22% more intense* (range: +5 to +34%) by the 2080s.
* Top 1% of daily rainfall totals in western WA & OR
Morerain,NOTbiggerstorms
FIG. 2. CMIP5 RCP 8.5 10-model means (boldface lines) for (a),(b) 99th percentile IVT(upper values, solid) and winter mean (lower values, dashed) for (left) 1970–99 (boldface blue)and (right) 2070–99 (boldface red) along the 13-grid-box transect in Fig. 1. Only October–March is considered. Light blue and red lines are individualmodels, and boldface green lines onthe left are NCEP–NCAR reanalysis values for 1970–99. Right-hand plots also show themultimodel means of the historic period for reference (boldface blue lines, same on left andright). Similar plots for (c),(d) IWV; (e),(f) 850-hPa total wind; and (g),(h) daily precipitationare also shown.
122 JOURNAL OF HYDROMETEOROLOGY VOLUME 16
2080s
1980s
MoreWaterVapor
Morerain,NOTbiggerstorms
FIG. 2. CMIP5 RCP 8.5 10-model means (boldface lines) for (a),(b) 99th percentile IVT(upper values, solid) and winter mean (lower values, dashed) for (left) 1970–99 (boldface blue)and (right) 2070–99 (boldface red) along the 13-grid-box transect in Fig. 1. Only October–March is considered. Light blue and red lines are individualmodels, and boldface green lines onthe left are NCEP–NCAR reanalysis values for 1970–99. Right-hand plots also show themultimodel means of the historic period for reference (boldface blue lines, same on left andright). Similar plots for (c),(d) IWV; (e),(f) 850-hPa total wind; and (g),(h) daily precipitationare also shown.
122 JOURNAL OF HYDROMETEOROLOGY VOLUME 16
2080s1980s
NochangeinWinds
Whatdoesthismeanforus?
Source: Kitsap Sun
“Downscaling”relatesthelargetothesmall
~100-200km(~60-120mi)resolution
~6km(~4mi)resolution
ResultsfromStatisticalDownscaling
WarmBasinsColdBasins
Salathéetal2014
Itmattershowyoudoit.
2040s,A1B
WarmBasinsColdBasins
Salathéetal2014
ResultsfromDynamicalDownscaling
Itmattershowyoudoit.
2040s,A1B
RegionalClimateModelProjections
https://twitter.com/LigaDos32
Findings:ChangeinHeavyRains
Howwelldoweknowourcurrentrisk?
“100-yearevent”
Heavy Rains at Sea-Tac
Low-End Projection High-End Projection
24-hour Rainfall
Changeinthe100-yrstorm
Whatdoesthismeanforflooding?
kingcounty.gov
Green,Snoqualmie,andSouthForkSkykomish rivers
Ashiftfromsnowtorainforbothrivers
Snoqualmie GreenWinter(Dec-Feb)
+10% +16%
Summer(Jun-Aug)
-70% -60%
(tableliststheminimumchangeamongthetwoprojections,relativetotheaveragefor1970-1999)
Changeinaveragestreamflowforeachseason,2080s:
SnoqualmieRiverfloods,2080s:
(USGSsite:SnoqualmieRNearSnoqualmie)
Isfloodingactuallydecreasing?
GreenRiverfloods:
ChangeinPeakFlow
s(%)
(3-hourflows) (dailyflows)
NoDam Dam
Outlook:What’snext?
• MoreRegionalModelProjections
• SamemodelingforWhite/Cedar
• Futurefloodmapping
seattletimes.com
fema.gov
[email protected](206)685-0317
VictoriaPinheiro,UW
https://cig.uw.edu/our-work/applied-research/heavy-precip-and-stormwater/https://cig.uw.edu/our-work/applied-research/effect-of-climate-change-on-flooding-in-king-county-rivers/
Isfloodingactuallydecreasing?