Mapping floodplains in the continental US for conservation ...
Transcript of Mapping floodplains in the continental US for conservation ...
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Mapping floodplains in the continental US for conservation and risk reduction.
Kris Johnson, The Nature Conservancy Joe Fargione, TNC
Paul Bates & Oliver Wing, University of BristolChristopher Sampson & Andrew Smith, SSBN Ltd.
May 4, 2017
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Risk Reduction & Resilience
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Risk Reduction & Resilience: The Threats
Iowa 2008Washington 2012
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Risk Reduction & Resilience: Nature based solutions
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Our WorkPolicy Partnerships Science & Engineering
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Hamilton City, CA Gulf of MexicoPuget Sound, WA
Our Work
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Getting to scale
• Fill gaps in existing floodplain data
• Additional flood frequencies
• Inform regional planning & prioritization
• Low-cost alternative to standard flood modeling approaches
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NEW US model
• 30 m DEM
• LISFLOOD-FP routes flows through channels delineated by HydroSHEDS
• Regionalized flood frequency analysis
• 10 return periods from 5 to 1000 yrs
• Explicit representation of USACE NLD
• Methodology replicated globally with lower quality data (Sampson et al. 2015)
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Large-scale flood modeling of continental US
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Large-scale flood modeling of continental US
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FEMA Data
• Amalgamation of local studies mapping the 1 in 100 year flood extent
• High level of agreement between FEMA and SSBN:
82% of SFHA capturedCSI = 0.55
• performance in dominant climates:Continental: H = 78%, C = 0.48Temperate: H = 84%, C = 0.59Arid: H = 73%, C = 0.43
Large-scale flood modeling: validation
Wing et al in review
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USGS Data
• 10 highly accurate local studiesLiDAR DEMs
surveyed bathymetry
usually 3m resolution
calibrated
• Design events with a 100-year recurrence interval selected
• other sites had further data on design events of varying magnitude
Large-scale flood modeling: validation
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USGS Data: Results (1 in 100)
LOCATION H (%) CSI
Albany, GA 93 0.76
Columbus, IN 83 0.82
Greenville, SC 100 0.70
Hattiesburg, MS 94 0.90
Minneapolis, MN 91 0.65
Ridgewood, NJ 87 0.83
Large-scale flood modeling: validation
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LOCATION H (%) CSI
Killbuck, OH(1 in 5)
87 0.85
Harrisburg, PA(1 in 10)
96 0.84
Battle Creek, MI(1 in 50)
99 0.54
Lincolnshire, IL(1 in 500)
54 0.53
Large-scale flood modeling: validation
USGS Data: Results (1 in X)
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Large-scale flood model application
Quantifying exposure in the continental US:
How many people are at risk?
What lands are exposed to potential flooding?
How might exposure increase with future development?
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Quantifying exposure in the continental US
How many people are at risk?
EPA dasymetric population data set
distributes 2010 US census to 30mpixels based on: census block, land cover, slope
RETURN PERIOD
EXPOSURE (MILLIONS)
EXPOSURE (%)
1 in 5 12.7 4.1
1 in 20 24.7 8.1
1 in 100 40.7 13.3
1 in 500 61.4 20.0
FEMA (1 in 100)
8.3 2.7
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Quantifying exposure in the continental US
What lands are exposed to flooding?
National Land Cover Data Set
Protected Areas Database of the US
EPA land-use projections & development scenarios
USACE National Structural Inventory
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Quantifying exposure in the continental US
Return period
ALL “natural” LULC classes in the floodplain
(area in km2)
UNPROTECTED “natural” LULC classes in the floodplain
(area in km2)
1 in 5 578,738 469,668
1 in 20 845,271 670,990
1 in 100 1,101,945 856,800
1 in 500 1,363,292 1,045,544
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Scenario Return periodExposed Developed
Area (km2)Assets at risk
(trillions of 2017 USD)
SSP2 (Low) 20501 in 5 65,632 3.91
1 in 100 136,202 9.42
SSP5 (High) 20501 in 5 75,357 4.24
1 in 100 155,692 10.28
SSP2 (Low) 21001 in 5 74,380 4.28
1 in 100 155,303 10.47
SSP5 (High) 21001 in 5 99,409 5.72
1 in 100 207,966 14.05
Quantifying exposure in the continental US
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Freshwater Network Floodplain Explorer