Integration of Coastal Inundation Modeling from Storm
Tides to Individual waves
Kwok Fai Cheung, PhD, PE
Department of Ocean and Resources Engineering
University of Hawaii at Manoa
The Second International Workshop on the Application of
Fluid Mechanics to Disaster Reduction
IRIDeS, Tohoku University
Sendai, Japan
March 16, 2015
Coastal Flood Hazards due to
Tropical Cyclones
Hurricane Iniki 1992
Long time-scale processes
• Barometric, wind, and wave setup
• Astronomical tide
Short time-scale processes
• Wave runup
Coastal Inundation
• Combined effects of barometric, wind,
wave setup, astronomical tide, and
runup
Image courtesy of NWS
Model Package
Case Study: Hurricane Iniki in1992
NEOWAVE + WAVEWATCH III + SWAN
• NEOWAVE: nonhydrostatic long-wave model for
astronomical tides and barometric and wind setup
• WAVEWATCH III: Global and regional waves with CFS
Reanalysis winds and parametric hurricane models
• SWAN: adapted for wave setup
• 2-way coupling and grid nesting
5 km resolution
BOSZ
• Optional module used instead of SWAN
• Boussinesq model for wave-by-wave runup simulation
500 m resolution
50 m resolution
4~10 m resolution
Hurricane Iniki 1992
51001
51003
51002
51004
Hurricane Iniki 1992
51001
51003
51004
51002
Hurricane Iniki 1992
Coupling of Tide, Surge, and Wave Setup
Tide-surge Coupling in Hawaii Region
Tide, Surge &Wave Setup Coupling at Nearshore
Comparison with records at Port Allen tide gauge
Linkage to Phase-resolving Wave Processes
Important for Steep Volcanic Slopes of Hawaii
• The Port Allen tide gauge recorded 1.4 m (above MSL) of maximum surface elevation
during Hurricane Iniki
• Floodwater reached 4 to 6 m elevation with maximum of 8 m indicative of wave runup
NEOWAVE + SWAN
• Storm surge (barometric and wind setup) and offshore wave spectra for BOSZ
simulation of phase-resolving wave process
Transfer of Storm Surge to BOSZ
• Quasi-steady, spatially-variable
storm surge elevation  for
modeling of individual wave
propagation
• Residual terms, gD/x and
gD/y, from the long-wave
equations with the assumption,
U, V, and /t = 0
• Additional source terms,
gD/x and gD/y, in the
Boussinesq equations to
maintain the storm surge in the
domain
Black line: MSL coastline; White dots: debris line
Summary
Incorporation of basin-scale processes in regional modeling of
storm surge and wave setup
Modeling of individual wave processes on quasi-steady, spatiallyvarying storm surge elevation
Li, N., Roeber, V., Yamazaki, Y., Heitmann, T.W., Bai, Y., and Cheung,
K.F. (2014). Integration of coastal inundation from storm tides to
individual waves. Ocean Modelling, 83, 26-42.