Donald T. Resio

A High-Resolution Coupled Riverine Flow, Tide, Wind, Wind Wave, and Storm Surge Model for Southern Louisiana and Mississippi. Part I: Model Development and Validation

Abstract A coupled system of wind, wind wave, and coastal circulation models has been implemented for southern Louisiana and Mississippi to simulate riverine flows, tides, wind waves, and hurricane storm surge in the region. The system combines the NOAA Hurricane Research Division Wind Analysis System (H*WIND) and the Interactive Objective Kinematic Analysis (IOKA) kinematic wind analyses, the Wave Model (WAM) offshore and Steady-State Irregular Wave (STWAVE) nearshore wind wave models, and the Advanced Circulation (ADCIRC) basin to channel-scale unstructured grid circulation model. The system emphasizes a high-resolution (down to 50 m) representation of the geometry, bathymetry, and topography; nonlinear coupling of all processes including wind wave radiation stress-induced set up; and objective specification of frictional parameters based on land-cover databases and commonly used parameters. Riverine flows and tides are validated for no storm conditions, while winds, wind waves, hydrographs, and high wa...

The Influence of Storm Size on Hurricane Surge

Over the last quarter-century, hurricane surge has been assumed to be primarily a function of maximum storm wind speed, as might be estimated from the Saffir–Simpson hurricane scale. However, Hurricane Katrina demonstrated that wind speed alone cannot reliably describe surge. Herein it is shown that storm size plays an important role in surge generation, particularly for very intense storms making landfall in mildly sloping regions. Prior to Hurricane Katrina, analysis of the historical hurricane record evidenced no clear correlation between surge and storm size, and consequently little attention was given to the role of size in surge generation. In contrast, it is found herein that, for a given intensity, surge varies by as much as 30% over a reasonable range of storm sizes. These findings demonstrate that storm size must be considered when estimating surge, particularly when predicting socioeconomic and flood risk.

Modeling the physics of storm surges

Despite the potentially catastrophic consequences of storm surges, the physics of surge generation and propagation has historically been poorly understood, and many misconceptions about surges still exist.

Evaluation of Contemporary Ocean Wave Models in Rare Extreme Events: The “Halloween Storm” of October 1991 and the “Storm of the Century” of March 1993

Abstract Two recent severe extratropical storms, the “Halloween storm” of October 26–November 2 1991 (HOS) and the “storm of the century” (SOC) of March 12–15 1993, are characterized by measurements of sea states of unprecedented magnitude off the east coast of North America. A Canadian buoy moored in deep water south of Nova Scotia recorded peak significant wave heights (HS) exceeding 16 m in both storms. In SOC, a NOAA buoy moored southeast of Cape Hatteras recorded a peak HS of 15.7 m, a record high for NOAA buoys. These extreme storm seas (ESS) exceed existing estimates of the 100-yr estimated design wave in these regions by about 50%. The extensive wave measurements made in both storms from buoys moored in deep water provide a rare opportunity to validate modern ocean wave models in wave regimes far more severe than those used for model tuning. In this study, four widely applied spectral wave models (OWI1G, Resio2G, WAM4, and OWI3G) are adapted to the western North Atlantic basin on fine mesh grids a...

Weakly turbulent laws of wind-wave growth

The theory of weak turbulence developed for wind-driven waves in theoretical works and in recent extensive numerical studies concludes that non-dimensional features of self-similar wave growth (i.e. wave energy and characteristic frequency) have to be scaled by internal wave-field properties (fluxes of energy, momentum or wave action) rather than by external attributes (e.g. wind speed) which have been widely adopted since the 1960s. Based on the hypothesis of dominant nonlinear transfer, an asymptotic weakly turbulent relation for the total energy e and a characteristic wave frequency ω* was derived eω 4 g 2 αss = ω 3 .de/dt g 2 ) 1/3 g 2 g2 ) The self-similarity parameter α ss was found in the numerical duration-limited experiments and was shown to be naturally varying in a relatively narrow range, being dependent on the energy growth rate only. In this work, the analytical and numerical conclusions are further verified by means of known field dependencies for wave energy growth and peak frequency downshift. A comprehensive set of more than 20 such dependencies, obtained over almost 50 years of field observations, is analysed. The estimates give α ss very close to the numerical values. They demonstrate that the weakly turbulent law has a general value and describes the wave evolution well, apart from the earliest and full wave development stages when nonlinear transfer competes with wave input and dissipation.

Implications of an f−4 equilibrium range for wind-generated waves

Abstract The existence of an f−5 equilibrium range was hypothesized for middle to high frequencies for a well-developed sea generated by the physical parameters of gross sea state in the pioneering work of Phillips. Various experimental studies since then, notably JONSWAP, have shown that if the power law is −5, then the proportionality constant is frequency dependent. Recent Lake Ontario data has shown an f−4 variation, which agrees with models of the equilibrium range as a Kolmogorov cascade. From this, the JONSWAP fetch relation and appropriate Assumptions about momentum transfer are shown to imply an important new spectra form for energy transfer from wind to wave, which differs slightly from other recent attempts. With suitable parameter relations, the midrange spectral energy can be shown to be essentially the same as its well known f−5 counterpart.

The Estimation of Wind-Wave Generation in a Discrete Spectral Model

Abstract The estimation of wind-wave generation using a new discrete spectral model is compared to Hasselmann et al.s (1976) parametric model and to models driven primarily by direct transfer of energy from the atmosphere into the surface waves. The main source term in this new model is a new parameterization of the net energy transfer due to nonlinear wave-wave interactions. After calibration of the wave-wave interaction source term to resemble the form of the solution to the complete Boltzmann integrals, the discrete spectral model is able to reproduce the fetch-limited results of Hasselmann et al. and fits well within the envelope of duration-limited growth curves from recent investigations. Since this model is discretized into frequency and direction components, a finite-difference scheme is used to model propagation effects. The formulation of this model allows simulations in oceanic conditions to consider both wave growth under local winds and swell decay of waves passing through a region simultane...

Systematic Variations in Inshore Bathymetry

To specify and characterize systematic regional variations in inshore bathymetry, the eigenvectors of 504 profiles of the U.S. Atlantic and Gulf coasts were calculated. The first three eigenvectors calculated account for over 97% of the topographic variance. The first eigenvector represents nearly linear departures from the mean; the second and third eigenvectors represent curvilinear bathymetrie variation; i.e., bar/trough morphology. The orthogonality of the linear slope and curvilinear bar/trough forms does not support the concept of a functional relationship between slope and the frequency of bars. In addition no relationship was revealed between inshore bar/trough morphology and offshore slope within nine miles (14 km) of the shoreline.

Nonlinear energy fluxes and the finite depth equilibrium range in wave spectra

Results using a finite depth representation of Webbs [1978] transformation of Herterich and Hasselmanns [1980] equation for the rate of change of energy density in a random-phase, spatially homogeneous, finite depth wave spectrum show that the equilibrium range in finite depth preserves a k−2.5 form consistent with Resio and Perries [1991] deepwater results and that the relaxation time toward an equilibrium range in shallow water is considerably faster than in deep water. Results from this finite depth nonlinear energy transfer representation compared to previously calculated results of analytical spectral situations show agreement, and the finite depth Zakharov [1968] and Herterich and Hasselmann [1980] forms are shown to be numerically equivalent. Spectral analyses of matching wave spectra sets at sites in 8 and 18 m depths at Duck, North Carolina, show a k−2.5 shape in the equilibrium range and show energy gains above the spectral peak and at high frequencies with energy loss in the midrange of frequencies near the spectral peak, consistent with four-wave interactions. Spectral energy losses between these two sites correlate with spectral energy fluxes to high frequencies, again consistent with four-wave interactions. The equilibrium range coefficient shows strong dependence on friction velocity at both gages.

Coexistence of weak and strong wave turbulence in a swell propagation

By performing two parallel numerical experiments-solving the dynamical Hamiltonian equations and solving the Hasselmann kinetic equation-we examined the applicability of the theory of weak turbulence to the description of the time evolution of an ensemble of free surface waves (a swell) on deep water. We observed qualitative coincidence of the results. To achieve quantitative coincidence, we augmented the kinetic equation by an empirical dissipation term modeling the strongly nonlinear process of white capping. Fitting the two experiments, we determined the dissipation function due to wave breaking and found that it depends very sharply on the parameter of nonlinearity (the surface steepness). The onset of white capping can be compared to a second-order phase transition. The results corroborate the experimental observations of Banner, Babanin, and Young.