Wave height

About: Wave height is a research topic. Over the lifetime, 5920 publications have been published within this topic receiving 100257 citations.

Wave height from planing and semi‐planing small boats

Abstract: The increasing number of small boats has raised concerns about their effects on the environment, particularly their waves. Bank erosion is one of the foremost concerns of boat waves but disruption of habitat, resuspension of bottom sediments, and damage to aquatic plants are other areas of concern. A large programme of field measurement of boat waves was conducted on Johnson Lake in Alaska to evaluate boats typically used on the Kenai River. The boat wave study compared wave characteristics of four boats under a variety of loadings, speeds, distances and motor powers. Over 400 tests were run on Johnson Lake with each test providing wave measurement at four locations. Two measures of waves and two types of tests were used in the study. MAXPOW was the wave height at the maximum power of the motor. MAXWAV was the maximum wave height produced by the boat which required runs at a range of speeds to determine the MAXWAV. While the MAXWAV data herein have considerable scatter in magnitude, the conditions at which MAXWAV occurs are consistent from boat to boat. To prevent generation of maximum wave heights, small boats should operate as far as possible either above or below length Froude number of 0.6, displacement Froude number of 1.3, or beam Froude number of 1.0. A general boat wave height equation was developed for the four boats based on boat speed, volume displaced by the boat and distance from the boat, and are applicable to semi-planing and planing boats based on MAXPOW and MAXWAV data. The predictive equation for V-hull boats was compared to independent data not used in the development and was found to be in agreement with the data. The predictive equation is limited to depth/boat length greater than 0.35. Published in 2005 John Wiley & Sons, Ltd.

An Algorithm for Estimation of Wave Height From Shadowing in X-Band Radar Sea Surface Images

Abstract: Directional wave spectra and integrated wave parameters can be derived from X-band radar sea surface images. The calibration of such spectra has until now depended on various empirical and semiempirical methods, which also require an external reference increasing the total expenses of operation. A novel algorithm, which is fully based on theory, producing reasonable estimates of the significant wave height based on shadowing in the images, has been now developed. The method does not require any reference measurements, and with that, enables automatic calibration of spectra from radar sea surface images, as well as the potential for reduced operational cost and increased accuracy of such wave-monitoring systems. Promising results are obtained with data acquired at a test site in the North Sea. Further work is, however, required to refine the algorithm and to test it under varying circumstances at various sites.

Data assimilation and bathymetric inversion in a two‐dimensional horizontal surf zone model

Abstract: [1] A methodology is described for assimilating observations in a steady state two-dimensional horizontal (2-DH) model of nearshore hydrodynamics (waves and currents), using an ensemble-based statistical estimator. In this application, we treat bathymetry as a model parameter, which is subject to a specified prior uncertainty. The statistical estimator uses state augmentation to produce posterior (inverse, updated) estimates of bathymetry, wave height, and currents, as well as their posterior uncertainties. A case study is presented, using data from a 2-D array of in situ sensors on a natural beach (Duck, NC). The prior bathymetry is obtained by interpolation from recent bathymetric surveys; however, the resulting prior circulation is not in agreement with measurements. After assimilating data (significant wave height and alongshore current), the accuracy of modeled fields is improved, and this is quantified by comparing with observations (both assimilated and unassimilated). Hence, for the present data, 2-DH bathymetric uncertainty is an important source of error in the model and can be quantified and corrected using data assimilation. Here the bathymetric uncertainty is ascribed to inadequate temporal sampling; bathymetric surveys were conducted on a daily basis, but bathymetric change occurred on hourly timescales during storms, such that hydrodynamic model skill was significantly degraded. Further tests are performed to analyze the model sensitivities used in the assimilation and to determine the influence of different observation types and sampling schemes.

Comparison of Spectral Refraction and Refraction-Diffraction Wave Models

Abstract: Wave energy estimated from linear, spectral wave propagation models incorporating refraction and refraction‐diffraction are compared over two bottom configurations: an analytic circular shoal and relatively smooth coastal bathymetry from San Diego, California. The agreement between the two models improves with an increase in the width of the incident directional spectrum and with a decrease in the complexity of the local bathymetry. There are, however, significant differences between the model transformations of directionally narrow spectra on both bathymerries. Pure refraction models are not quantitatively accurate in these cases. These comparisons also demonstrate the importance of directional wave spreading in transformations over even relatively simple natural bathymetry. Data from a fundamentally low‐resolution pitch‐and‐roll buoy, if used as the sole source of directional information for incident waves, can lead to significant uncertainty in wave heights estimated by the refraction‐diffraction model.