Hurricane Sandy Inundation Probabilities:Hurricane Sandy Inundation Probabilities:Today and TomorrowToday and Tomorrow

W. Sweet, C. Zervas, S. Gill and J. Park (2013)W. Sweet, C. Zervas, S. Gill and J. Park (2013)

Joseph Park William SweetJoseph Park William SweetNational Oceanic and Atmospheric Admin.National Oceanic and Atmospheric Admin.

National Ocean ServiceNational Ocean Service

Sandy was a superstorm, unique by many measures.

The onshore impact angle was extremely rare. Return Interval = 714 years

(95% confidence range 435 to 1429)Timothy M. Hall, Adam H. SobelGeophysical Research LettersVolume 40, Issue 10, pages 2312–2315, 28 May 2013

From: wunderground

The storm’s NE quadrant funneled a massive storm surge up NY Harbor and Long Island Sound.

Storm surge: obs – pred tideSandy hit at peak high tide.

Battery Park, NYtheepochtimes.com

Hoboken NJ

Sweet et al. (2013)

Heights above MHHW

Stars indicate highest Stars indicate highest storm tide ever observedstorm tide ever observed

NCAR/UCARBob HensonDecember 31, 2012

Flood risk is increasing as the decades-old infrastructure steadily loses ground from relative sea level rise (SLRrel).

Parris, A., P. Bromirski, V. Burkett, D. Cayan, M. Culver, J. Hall, R. Horton, K. Knuuti, R. Moss, J. Obeysekera, A. Sallenger, and J. Weiss. 2012. Global Sea Level Rise Scenarios for the US National Climate Assessment. NOAA Tech Memo OAR CPO-1. 37 pp.

Parris, A., P. Bromirski, V. Burkett, D. Cayan, M. Culver, J. Hall, R. Horton, K. Knuuti, R. Moss, J. Obeysekera, A. Sallenger, and J.

Weiss. 2012. Global Sea Level Rise Scenarios for the US National Climate Assessment. NOAA Tech Memo OAR CPO-1. 37 pp.

Gulfstream

Intergovernmental Panel on Climate Change (IPCC) 2007.

Sea Level Monitoring and NOAA Tide GaugesSea Level Monitoring and NOAA Tide Gauges

NOAA’s National Water Level Observation Network (NWLON)

• Relative measurements

• Tidal-geodetic connection

• Sea level trends

• Vertical land motion

• Extreme events

Product: Long-term Product: Long-term relativerelative Sea Level Trends Sea Level Trends http://tidesandcurrents.noaa.gov/sltrendshttp://tidesandcurrents.noaa.gov/sltrends

Relative SLR and Vertical Land Motion (VLM)Relative SLR and Vertical Land Motion (VLM)

GaugeAltimeterAltimeter

-10 -8 -6 -4 -2 0 2 4 6 8 10mm/yr

SLR rates (1992-2010)

http://~/publications/Technical_Report_NOS_COOPS_065.pdf

Zervas, Gill and Sweet (2013)Zervas, Gill and Sweet (2013)VLM is an important contributor to VLM is an important contributor to relative SLR, especially within the relative SLR, especially within the mid-Atlantic and Gulf Coast regionsmid-Atlantic and Gulf Coast regions

Product: Extreme Water Level ProbabilitiesProduct: Extreme Water Level Probabilitieshttp://tidesandcurrents.noaa.gov/est/http://tidesandcurrents.noaa.gov/est/

• Data detrended (relative mean seal level) prior to analysisData detrended (relative mean seal level) prior to analysis

• Sandy’s impacts levels are “fixed elevations” in timeSandy’s impacts levels are “fixed elevations” in time

• 1950 probabilities: model lowered by historical relative trend1950 probabilities: model lowered by historical relative trend

• Future (2050, 2100) probabilities using relative “Scenarios”Future (2050, 2100) probabilities using relative “Scenarios”

• No wave runup/setup: ~ to FEMA’s Stillwater ElevationsNo wave runup/setup: ~ to FEMA’s Stillwater Elevations

Quasi-stationary approachQuasi-stationary approach

F(x; μ, σ, ξ) = F(x; μ, σ, ξ) = exp { - [ 1 + ξ(x-μ)/σ ]exp { - [ 1 + ξ(x-μ)/σ ]-1/ξ-1/ξ } }

μμ: location (median): location (median)

σσ: scale (spread): scale (spread)

ξξ: shape (of upper tail): shape (of upper tail)

Generalized Extreme Value (GEV) of Annual Max ObsGeneralized Extreme Value (GEV) of Annual Max ObsGeneralized Extreme Value (GEV) of Annual Max ObsGeneralized Extreme Value (GEV) of Annual Max Obs

Probability of a “Sandy-level event” is now significantly higher (return intervals lower) than in 1950 from SLRrel. A smaller storm surge is now required to innundate similar elevations.

Sweet et al. (2013)

Like rolling dice, but steadily losing number of sides…

Return Interval decay as a function of NCA SLRReturn Interval decay as a function of NCA SLRrel rel scenarios:scenarios:Less powerful storms with smaller storm surge than Sandy Less powerful storms with smaller storm surge than Sandy will innundate similar levels…will innundate similar levels…

years years

2050 2100

Sweet et al. (2013)

Time-dependent Sandy-impact level Return Intervals Time-dependent Sandy-impact level Return Intervals Time-dependent Sandy-impact level Return Intervals Time-dependent Sandy-impact level Return Intervals

Return Interval (years)

To Conclude

• Hurricane Sandy was an extreme event. While rare, the probabilities (risk) of similar event impacts have and will continue to increase as sea level rises.

• Climate-change related sea level rise reduces the expected time between these extreme events at a given location.

• Models of Sea Level Rise (projections) are being used with statistical models to inform Government and Policy decision makers with estimates of future risk.