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Floodplain Management Association Conference 2017
Floodplain Management Association 2017
Mountain View Storm Drain Master PlanClimate Change and Rainfall Statistics
James Gregory, PE, ESA, 9/7/2017
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Floodplain Management Association Conference 2017
Project overview
• The City is working to establish a prioritized CIP to reduce flood risk in Mountain View
• The CIP includes evaluating future climate scenarios for a Storm Drain Master Plan
• ESA developed a climate tool linking MATLAB and GIS to estimate changes in rainfall intensity-duration-frequency under effects of climate change
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Floodplain Management Association Conference 2017
Climate change background
• General circulation models
wikipedia.org Cal-adapt.orgAdapted from IPCC, 2014
• Emissions scenarios− SRES (replaced)− RCPs (IPCC AR5)
• Downscaling− Dynamic− Statistical
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Floodplain Management Association Conference 2017
• More frequent, and stronger, tropical cyclones• Uncertain effect on winter extratropical cyclones• More frequent, and heavier, atmospheric river events• Accelerating sea level rise (WAIS)
Emanuel 2013
Lehmann 2014
Jeon 2015
Climate change trends in California
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Floodplain Management Association Conference 2017
Climate Data Sources
Existing data New Data
WCRP CMIP5/CMIP3 Cal-Adapt California Climate
CommonsCMIP5 GCM
data Scripps LOCA
Resolution 12km 12km 270m 100km 4km
Spatial coverage CONUS California and Nevada California Global CONUS
Temporal coverage 1950-2100 1950-2100 1950-2100 1950-2100 1950-2100
Available variables
Raw data -temperature,
rainfall, hydrologic
Raw and post-processed -
temperature, rainfall, hydrologic, wind, fire
Post-processed -temperature, rainfall,
hydrologic
Raw data -temperature,
rainfall
Raw data –temperature,
rainfall, hydrologic
Number of GCMs 20+ 4 2 56 32
Data access http://gdo-dcp.ucllnl.org/ http://cal-adapt.org/ http://climate.calcommo
ns.org/
https://esgf-data.dkrz.de/projects/cmip5-
dkrz/
http://gdo-dcp.ucllnl.org/
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Floodplain Management Association Conference 2017
Problem statement
• The need for floodplain managers to plan for climate change impacts is increasing
• Guidance is lacking with respect to quantifying the impact of climate change on rainfall
• Data resources exist to quantify change in climate conditions
• How to leverage this data to inform resource planning?
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Floodplain Management Association Conference 2017
Future IDF curves
2100 high 100yr depthEC 100yr depth
Hydrologic Model
Hydraulic model Floodplains
Future IDF Spatial Data
General approach
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Floodplain Management Association Conference 2017
• Typically available at County Level• Also available digitally from NOAA (Atlas 14)
Santa Clara County (2006) NOAA Atlas 14
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=ca
Intensity-duration-frequency curves
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Floodplain Management Association Conference 2017
• Daily rainfall gridded data from 1950-2100 − ~60,000 grids/model
• 30 GCM model runs and 2 climate scenarios − ~3.6M grids of rainfall data
• Historic period used to train models from 1950-2005• Data downscaled to 12km resolution for CONUS• BCCA downscaled data used
Daily total rainfall, BCCA access1-0 GCM, July 07, 1957
Data
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Floodplain Management Association Conference 2017
0.1
1.0
10.0
0.0100.1001.000Peak
ann
ual r
ainf
all (
in)
Probability
Annual MaximaGEV fit
0.1
1.0
10.0
0.0100.1001.000
Peak
ann
ual r
ainf
all (
in)
Probability
Annual MaximaGEV fit
Historic frequency Future frequency, 2067 RCP4.5
Climate data frequency analysis
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Floodplain Management Association Conference 2017
Model distribution
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Emissions scenario Recurrence interval Year Climate model distribution statistic
Percent change in rainfall depth
RCP 8.5
10-year
2067
Mean 17%
Mean + 1SD 30%
Mean + 2SD 43%
2100
Mean 25%
Mean + 1SD 42%
Mean + 2SD 58%
100-year
2067
Mean 20%
Mean + 1SD 46%
Mean + 2SD 71%
2100
Mean 26%
Mean + 1SD 53%
Mean + 2SD 80%
Data output
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Floodplain Management Association Conference 2017
Further Applications
• Sizing new stormwater infrastructure to accommodate future climate conditions
• Understand future level of service for existing infrastructure• Estimate timing over which existing infrastructure will need
to be upgraded• Develop future climate conditions IDF curves and spatial
data for hydrology guidelines
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Floodplain Management Association Conference 2017
Questions - Contact• James Gregory, PE
− [email protected]− 510.463.6742
• Carlos Diaz, PE− [email protected]
• 707.285.0586