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Modeling and Mapping the Advance of Monthly Tidal Flooding
A Possible Threshold of Inhabitability
Philip Orton, Stevens Institute of Technology
Collaborators:Helen Cheng, New York Sea Grant and Science and Resilience Institute at
Jamaica Bay (SRIJB)Adam Parris, Brooklyn College (CUNY) and SRIJB
William Solecki, Hunter College, CUNYRadley Horton, Columbia University
Primary Funding: [email protected]
Surging Seas (Climate Central)
Motivation:
Sea level rise mappers based on daily high tide (MHHW) don’t represent the initial onset of future problems with “Sunny Day” tidal flooding àwe need a better metric of
tidal flooding!
A single tide gauge’s “minor flood” isn’t always representative of flood risk for an entire region – New York City is a great example (at right). à We need mapping
“We need granularity as to location [of tidal flooding]” – Mark Wilbert, today
What is a Useful Tidal Flood Metric?
• William Sweet’s work has revealed how nuisance flood occurrences are accelerating
• Sweet and Park (Earth’s Future, 2014) referred to “tipping point” in the advancement of impacts of 30 floods per year
à Is 30 days a tipping point indicator of uninhabitability, where adaptation must occur?
NPCC 2010, 2015, 2019 Reports
Published in the Annals of the New York Academy of Sciences
Climate Change Adaptation in New York City: Building a Risk Management Response: New York City Panel on Climate Change 2010 Report
Building the Knowledge Base for Climate Resiliency: New York City Panel on Climate Change 2015 Report
Advancing Tools and Methods for Flexible Adaptation Pathways and Science Policy Integration: New York City Panel on Climate Change 2019 Report
NPCC Sea Level Rise Projections
Antarctic Rapid Ice Melt (ARIM)
Monthly Tidal Flood Mapping with SLR: Methods Overview
• Simulation– Hydrodynamic model (regional model – NYHOPS)– 35 day simulation, mean streamflows, no wind– Simulate for present-day plus all SLR scenarios
• Computation– Tidal harmonic analysis - create tide-only timeseries– Compute mean of all monthly tidal maxima (MMHW)– Repeat analysis with USGS and NOAA tide gauge
observations– Bias-correct modeled MMHW to observations– Bathtub mapping from estuary model to inland flood zones
Observed water levels VS mean monthly and daily high water
data from the Battery tide gauge (Manhattan)
MHHW is a standard tidal datum
MMHW is not
NPCC Figure 4.B.6. Map (vs Longitude, Latitude) showing the difference between present-day tidal MMHW (monthly maximum) and MHHW (daily maximum) water levels.
The Battery
How Different is MMHW?
NPCC 2015/2019
Citizen Science/ Collaboration
Ongoing/Future Research• Collaborating with USGS (Ganju, Aretxabaleta)– Modeling the entire US East and Gulf Coast region’s tides
with sea level rise– Mapping future monthly tidal flooding as pilot studies
(Boston, Chesapeake, New Jersey)
• Also interacting with NOAA/ W. Sweet• Key questions:– What methods/models can be used for nationwide
monthly tidal flood mapping?– What is the best metric for mapping future frequent
floods? Is it MMHW? Minor flood level? The 1-month return period flood?
…. Define Uninhabitable!
NYC Government Response
• NPCC’s 100-year flood zones plus SLR are already used in some planning/zoning
• Was invited to meet with City Planning and Mayor’s Office of Resiliency in May– Not yet ready to add MMHW to their flood mapper or
planning• Having two tidal flood metrics may be confusing• Also, useful to wait for more research defining what tidal flood
metric is best
– We are collaborating to map MMHW with NPCC’s other SLR percentiles (10th, 25th, 75th)
Conclusions
• Across NYC, MMHW exceeds MHHW by 0.6-1.0 foot• MMHW is a substantially higher metric of tidal flooding,
flooding neighborhoods sooner as sea level rises• While MHHW is exceeded hundreds of times per year,
MMHW has only 20-35 exceedances per year and can better address a possible tipping point for habitability
• Mapping relatively frequent and observable monthly tidal flooding may be more helpful than mapping the rare 100-year flood, for communicating the impacts of sea level rise
Modeling and Mapping the Advance of Monthly Tidal Flooding
A Possible Threshold of Inhabitability
Philip Orton, Stevens Institute of Technology
Collaborators:Helen Cheng, New York Sea Grant and Science and Resilience Institute at
Jamaica Bay (SRIJB)Adam Parris, Brooklyn College (CUNY) and SRIJB
William Solecki, Hunter College, CUNYRadley Horton, Columbia University
Primary Funding: [email protected]
EXTRA SLIDES
http://stevens.edu/SFAS
http://stevens.edu/SFASSame NYHOPS model is applied in real-time ensemble flood forecasting
http://stevens.edu/SFAS
