MUMS: Coupling Uncertain Geophysical Hazards Workshop: Coastal Flooding Uncertainty, Attribution, and Communication - Taylor Asher, March 25, 2019
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Coastal flood hazards are amongst the deadliest and most costly natural disasters on the planet. Their underlying processes are, in some regards, in an advanced state of knowledge. Yet, the scale and variety of both causes and effects leave open many challenging questions. And our advanced state of knowledge has failed to realize a reduction in deaths or damages. In this talk, I will address the underlying physical processes of coastal flooding and knowledge gaps, with an eye toward current research and the overarching issue of turning knowledge to action.
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MUMS: Coupling Uncertain Geophysical Hazards Workshop: Coastal Flooding Uncertainty, Attribution, and Communication - Taylor Asher, March 25, 2019
- 1. Taylor Asher March 25, 2019 credit: Mike Groll, AP
- 3. 2019/03/25 3 Shallow water eqs. • (x,y,t) • (u,v,η) • Nonlin, 2nd order, inhomogeneous, coupled PDEs in rotating reference frame • 10-10,000 core-hours for typical simulation 2 2 0 e H e x H y Du fv g u Dt x Dv fu g v Dt y h hu hv t x y William Pringle & Keith Roberts U. Notre Dame
- 4. 2019/03/25 4
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- 6. 2019/03/25 6 https://www.nhc.noaa.gov/surge 2 2 e H e x H y Du fv g u Dt x Dv fu g v Dt y
- 7. • AEP annual (surge) exceedance probability • c vector of storm parameters, usually 5-10 • η surge elevation 2019/03/25 7 AEP |p P d c c c c
- 8. 1. Select parameters c 2. Calculate p(c) from historical data 3. Run simulations 4. Solve 2019/03/25 8 AEP |p P d c c c c
- 9. 1. Simulate climate 2. Extract, downscale relevant TCs 3. Run simulations 4. Solve 2019/03/25 9 0 20 40 60 80 100 120 140 160 870 920 970 1020 Radiusofmaxwinds(km) central pressure (mb) AEP |p P d c c c c
- 11. 2019/03/25 11
- 14. 2019/03/25 14
- 15. 2019/03/25 15
- 16. 2019/03/25 16
- 17. 2019/03/25 17
- 18. • Nadal-Caraballo, Norberto (2017). Quantification of Uncertainty in Probabilistic Storm Surge Models. 3nd Annual Probabilistic Flood Hazard Assessment Workshop, Rockville, MD – December 4-5, 2017. • Toro, G.R., 2008. Joint probability analysis of hurricane flood hazards for Mississippi. Risk Engineering, Inc. 2019/03/25 18
Editor's Notes
- $10 B/yr 1900-2005, but 2006-2018 has been 2x-3x that
- This is kinda what it looks like It’s messy, complicated We can’t/don’t model most of what you’re seeing Clever physics to simplify problem Spectral waves, wave action conservation (form of energy) Difficult to get at parameterization effects
- Brief overview of math, for those not interested, here’s a video of Cyclone Idai that recently devastated Mozambique (~1k dead) 3 eqs. (continuity + horiz. momentum), 3 indep vars, 3 unknowns RANS eqs., Boussinesq, incompressible 2D, depth-integrated horizontal momentum equations and continuity (mass conservation) equation u and v horizontal velocities, x and y horizontal coordinates, t time Variables: f the Coriolis parameter (the Earth spins so we’re in a rotating reference frame) h depth, g gravity, eta water elevation, nu an “effective” (eddy) viscosity term tau represents various stress terms for effects like bottom drag (frictional dissipation) and surface drag (wind stress)
- In spite of simplifications, things work well
- rare events means you’re data-starved, and don’t know what you’re missing until it pops up. if the world is too complicated to think of all the ways you might fuck up, then you’re always going to be estimating your error based on the ways you’ve fucked up so far, which means you’ll always been over-confident in how accurate you are... [Talk about issues of identifiability, use Ike example]
- But there’s only 40-160 yrs of data
- But GCMs aren’t that great
- Bottom curve is global climate model-based
- H. Katrina single vs. double distrib
- H. Sandy flooded subways and basements http://www.photofromtheworld.com/img/Photo/Event/Natural%20Disaster/2012%20Hurricane%20Sandy/Bowling%20Green%20subway%20station%20in%20Battery%20Park%20in%20New%20York%20on%20October%2030,%202012.jpg
- Me late to SAMSI http://www.photofromtheworld.com/img/Photo/Event/Natural%20Disaster/2012%20Hurricane%20Sandy/Bowling%20Green%20subway%20station%20in%20Battery%20Park%20in%20New%20York%20on%20October%2030,%202012.jpg
- Florence 10 days out – a big storm might hit somewhere “ 5 days – a big storm will hit somewhere
- Florence 10 days out – a big storm might hit somewhere “ 5 days – a big storm will hit somewhere
- Florence 10 days out – a big storm might hit somewhere “ 5 days – a big storm will hit somewhere