Journal ArticleDOI
Wave variance partitioning in the trough of a barred beach
Reads0
Chats0
Abstract:
The wave-induced velocity field in the nearshore is composed of contributions from incident wind waves (f > 0.05 Hz), surface infragravity waves (f 2/g), where fis the frequency, = 2f, }c is the radial alongshore wavenumber (2re/L, L being the alongshore wavelength), [ is the beach slope, and g is the acceleration due to gravity. Using an alongshore array of current meters located in the trough of a nearshore bar (mean depth = 1.5 m), we investigate the bulk statistical behaviors of these wave bands over a wide range of incident wave conditions. The behavior of each contributing wave type is parameterized in terms of commonly measured or easily predicted variables describing the beach profile, wind waves, and current field. Over the 10-day period, the mean contributions (to the total variance) of the incident, infragravity, and shear wave bands were 71.5%, 14.3% and 13.6% for the alongshore component of flow (mean rms oscillations of 44, 20, and 19 cm s -1, respectively), and 81.9%, 10.9%, and 6.6% for the cross-shore component (mean rms oscillations of 92, 32, and 25 cm s -1, respectively). However, the values varied considerably. The contribution to the alongshore (cross-shore) component of flow ranged from 44.888.4% (58.5-95.8%) for the incident band, to 6.2-26.6% (2.5-32.4%) for the infragravity band, and 3.433.1% (0.6-14.3%) for the shear wave band. Incident wave oscillations were limited by depth-dependent saturation over the adjacent bar crest and varied only with the fide. The infragravity wave rms oscillations on this barred beach are best parameterized by the offshore wave height, consistent with previous studies on planar beaches. Comparison with data from four other beaches of widely differing geometries shows the shoreline infragravity amplitude to be a near-constant ratio of the offshore wave height. The magnitude of the ratio is found to be dependent on the Iribarren number, 0 = [(H/Lo) -1/2. Shear waves are, as previous observation and theory suggest (Oltman-Shay et al., 1989; Bowen and Holman, 1989), significantly correlated with a prediction of the seaward facing shear of the longshore current.read more
Citations
More filters
Journal ArticleDOI
Empirical parameterization of setup, swash, and runup
TL;DR: In this paper, an empirical parameterization for extreme runup, defined by the 2% exceedence value, has been developed for use on natural beaches over a wide range of conditions.
Journal ArticleDOI
The history and technical capabilities of Argus
Robert A. Holman,J. Stanley +1 more
TL;DR: In this article, the authors describe the components of the Argus Stations with an emphasis on quantitative characterization of the accuracies and resolution of system components, and present algorithms for estimation of a range of important nearshore measurements.
Journal ArticleDOI
Observations of swash under highly dissipative conditions
TL;DR: In this paper, the authors investigated the dependence of swash parameters on environmental conditions such as short-wave height, period, and local beach slope, and found evidence for saturation of the higher infragravity frequencies for ξ 0 less than, roughly, 0.27.
Journal ArticleDOI
Nonlinear evolution of shear instabilities of the longshore current: A comparison of observations and computations
TL;DR: In this article, the authors consider the generation of nearshore currents due to obliquely incident breaking waves, damping effects due to bottom friction, and diffusion effects caused by lateral momentum mixing caused by turbulence and depth-varying current velocities.
Journal Article
The behaviour of a multiple bar system in the nearshore zone of Terschelling, the Netherlands: 1965-1993
B.G. Ruessink,Aart Kroon +1 more
TL;DR: In this paper, the behavior of a multiple bar system in the nearshore zone of the island of Terschelling, the Netherlands, was investigated on the time scale of years using a data set of soundings.
References
More filters
Journal ArticleDOI
Radiation stresses in water waves; a physical discussion, with applications
TL;DR: The radiation stresses in water waves play an important role in a variety of oceanographic phenomena, for example in the change in mean sea level due to storm waves (wave set-up), the generation of "surf-beats", the interaction of waves with steady currents, and the steepening of short gravity waves on the crests of longer waves as discussed by the authors.
Journal ArticleDOI
Observations of bispectra of shoaling surface gravity waves
Steve Elgar,Robert T. Guza +1 more
TL;DR: In this paper, the authors elucidated the nonlinear dynamics of waves shoaling between 9 and 1 m water depths via the bispectrum and found that the biphase values associated with significant bicoherence levels in 9 m depth are consistent with Stokes-like nonlinearities, but as the water depth decreases the waves evolve through a slightly skewed shape somewhat asymmetrical to a vertical axis toward a highly asymmetrical unskewed sawtooth shape.
Journal ArticleDOI
Setup and swash on a natural beach
TL;DR: In this paper, the authors measured 154 runup time series measured on a moderately steep beach under incident waves varying from 0.4 to 4.0 m significant wave height, and found that the infragravity band appears to become dominant in the swash below some value of ξ0.
Journal ArticleDOI
Energy saturation and phase speeds measured on a natural beach
TL;DR: In this article, the authors measured wave height and speed from 7m depth shoreward and found that wave heights in the inner surf zone are strongly depth independent: the envelope of the wave heights is described by H/sub rms/ = 0.42 h, and the depth dependence of the breaking wave height is related to the kinematic instability criterion.
Journal ArticleDOI
Surf Zone Longshore Currents and Random Waves: Field Data and Models
TL;DR: In this paper, the longshore current models are based on balancing the gradient of the radiation stress with the alongshore bed shear and Reynold's stresses, assuming stationary wave conditions and straight and parallel bottom contours.