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In this study the numerical model Delft3D is implemented on high-resolution grids to evaluate beach morphological response to groins and submerged breakwaters under sea-breeze conditions. The numerical model is compared with field measurements from three sites on the northern Yucatan coast of Mexico. At these sites, relatively low energy waves with significant wave heights arrive at a steep oblique angle to the coast that drives high sediment transport rates. After calibration of the model, by adjustment of model free parameters, the model results show accurate representations of the diurnal variation of hydrodynamic conditions (wave height and current velocity) driven by the daily sea-breezes. Moreover, the morphodynamic model shows a good representation of the rapid morphological changes, particularly of the accretion pattern caused by a temporary groin and the subsequent recovery following the structure removal. However, erosion patterns at the downdrift areas of structures were not reproduced, owing to the numerical model limitations of simulating swash morphodynamics. Model validation with field observations of the beach response behind submerged breakwaters enabled the model to be used for a parametric study. Following previous work, new equations are developed in the present study that show an improvement for predicting shoreline changes near submerged breakwaters under sea-breeze conditions. Despite the limitations in reproducing downdrift erosion, overall the high-resolution modelling approach satisfactorily simulates the hydrodynamic and the updrift accretion responses to coastal structures on sandy beaches with oblique waves. • Simulations of beach change near groins and submerged breakwaters are performed. • Results are compared to measurements at three sites with high sediment transport rates. • New equations show improved prediction of shoreline change near submerged structures. [ABSTRACT FROM AUTHOR]

Medellín, G.; Mariño-Tapia, I., and Euán-Ávila, J., 2015. The influence of a seawall on postnourishment evolution in a sea-breeze-dominated microtidal beach. The postnourishment beach evolution is evaluated on a sea-breeze-dominated microtidal beach in Yucatan (Mexico). The study area has experienced severe beach erosion due to both alongshore sediment-transport gradients during calm conditions and offshore sediment transport during extreme wave events. Therefore, a shoreline restoration program, including beach nourishment and the removal of groynes, was carried out in 2002. Bimonthly subaerial/intertidal beach profiles measured during 7 years (2002-09), in front of a seawall and at an adjacent beach (nonwalled), are employed to analyze the beach nourishment evolution. Empirical orthogonal function (EOF) analysis of the shoreline time series is performed using the data extracted from the 50 field surveys. The temporal evolution of the EOF analysis shows the following: (1) an abrupt increase in beach width due to nourishment at the study site at the beginning of 2003, (2) followed by a sustained increase (from 2004 to 2007) owing to the sediment advection from a massive beach fill performed up-drift of the study area, and (3) a decrease in beach width from 2007 until the end of the study period. Moreover, the mean profile-volume change is estimated separately for walled and nonwalled beach sections. The nonwalled profiles results are consistent with the temporal evolution described by the EOF analysis. On the other hand, walled beach profiles show a net volume loss from 2002 to 2007, remaining stable during the following 3 years. Consistent with previous studies, seasonal variability of sand volume was found to be greater in front of the seawall with respect to the nonwalled section. Nevertheless, the erosional/despositional rates in the two sections show opposite trends during mean (sea-breeze) wave conditions, being more important in the subaerial beach profiles. The latter implies that swash-zone sediment transport represents an important contribution to the total sediment budget in the study area; hence, seawalls can significantly modify coastal dynamics in sea-breeze-dominated environments. [ABSTRACT FROM AUTHOR]

This paper presents a qualitative assessment of coastal processes along the northern coast of the Yucatan Peninsula based on a method used to estimate the potential longshore sediment transport. Despite the deep-water low-energy wave conditions (Hs = 1 m) in the study area, erosion is critical in many locations, including the urbanized stretches of coast. The waves were characterized using a 12 y (1997-2009) deep-water wave hindcast data (WAVEWATCH III) as forcing for a spectral wind-wave numerical model (MIKE 21 SW) used to propagate the waves to the coast. Simulated time series of significant wave height, peak period, and direction are compared against in situ measurements at 10 m water depth. Numerical results are further employed for estimation of the nearshore wave climate along the coast. Wave conditions are strongly affected by the wide continental shelf in front of the northern Yucatan Peninsula, with an increase in wave energy at the eastern part of the peninsula where the shelf narrows. The nearshore wave climate is employed for the qualitative assessment of potential longshore sediment transport (LITDRIFT model) in the study area. The sediment transport calculations are consistent with both volume impoundment estimations at a groin and dredging estimates at a harbor (-35,000 m³/y). A net westward potential longshore sediment transport is found along the entire coast, ranging between --20,000 and --80,000 m³/y, except west of Holbox, where longshore transport direction is inverted. Based on sediment transport gradients, potential erosion and deposition areas are identified. Erosion/accretion patterns at nonurbanized areas are consistent with field observations. This dominant westward longshore transport suggests an extremely sensitive shoreline to littoral barriers, as supported by observations in the most urbanized areas. These areas show no gradients on longshore sediment transport, whereas beach erosion is a common feature enhanced by littoral barriers. Shore protection should then be oriented toward sediment management strategies. [ABSTRACT FROM AUTHOR]