Irregular wave transformation and undertow for coastal structures in a surf zone

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references: p.56-58.Issued also on microfiche from Lange Micrographics.Laboratory measurements of free surface elevation and undertow velocity were made in front of a model revetment on a plane slope in shallow water to study the effects of the revetment on the wave transformation and undertow and to test the predictive capabilities of numerical wave transformation and undertow models. Irregular waves were generated from the TMA spectral form. Free surface oscillations were measured with wire resistance wave gages, and velocities were measured by acoustic Doppler velocimeter. The free surface and undertow measurements were compared to a previous study without a revetment to determine the effect of the structure on incident waves and undertow. Comparisons showed that for the case of a structure with 45% reflection, the wave transformation in the inner surf zone was unaffected and the undertow was slightly reduced. The reduction in undertow was found to exhibit some proportionality to the square of the reflection coefficient. The present and previous studies were compared to existing wave transformation and undertow models. Comparisons showed that the models performed as well for the case of 45% wave reflection as they did for the case of little wave reflection. Coupling of the wave transformation and undertow models through a calibration coefficient to account for the roller effects was presented, and the spatial and temporal variations of this coefficient were discussed