Ismael Mariño-Tapia

Effects of reef roughness on wave setup and surf zone currents

ABSTRACT Franklin, G.L., Mariño-Tapia, I. and Torres-Freyermuth, A., 2013. Effects of reef roughness on wave setup and surf zone currents. Circulation in reef systems controls an important number of key processes, such as the transport and dispersion of larvae, nutrients, and sediments. In fringing reef systems, where a shallow lagoon backs onto the reef crest, circulation appears to be dominated by wave breaking. Despite the identified importance of wave driven flows within reef systems, there is a lack of detailed knowledge on these processes within the surf zone of reef crests and the effects reef roughness has on these flows. A numerical study, using two-dimensional (2DV) simulations, was carried out in order to improve the understanding of wave-driven flows in the surf zone of a fringing reef. The model used is Cornell Breaking Wave and Structures (COBRAS), which solves the Reynolds-Averaged Navier-Stokes (RANS) equations with a turbulence closure scheme. The effect of different reef roughness on wave height, wave setup, infragravity waves and mean flows was studied. Model results revealed that wave setup increases significantly (~22%) with increasing bed roughness, consistent with prior studies on sandy beaches. Furthermore, cross-shore velocity structure is heavily affected by bed roughness. The latter implies that the coral reef flattening trend observed world-wide could result in a decrease in the circulation within the lagoon with important implications for reef health.

Post-nourishment beach scarp morphodynamics

ABSTRACT Ruiz de Alegria-Arzaburu, A., Mariño-Tapia, I., Silva, R., Pedrozo-Acuña A., 2013. Post-nourishment beach scarp morphodynamics Large and persistent beach scarps can be safety hazards to beach users and result in serious social and economic implications. In this study the morphological evolution of beach scarps of large dimensions is examined on a nourished microtidal Caribbean Mexican beach. Beach profiles were measured three-to-four monthly along the beach after the nourishment in December 2009 and over 1.5 years. A beach scarp was defined as a feature with a slope larger than the critical angle of repose of 32° and a minimum height of 0.25 m. The top and bottom positions of the scarps were calculated from the minimum and maximum values of the second derivative of the measured beach profiles (slope gradient). The cross-shore morphological evolution of the scarps was related to wave runup (R2) and tides, and also to both with the contribution of the longshore energy flux (Pl). During calm conditions characterised by longshore uniform mean and maximum R2 of 0.73 and 0.83 m, and Pl=180KN/s, the scarps remained present along the beach. Energetic conditions with mean and maximum R2 of 0.83 and 1.2 m and Pl=400KN/s, increased the longshore rythmicity of the beach and induced significant cross-shore erosion (over 20 m) and the disappearance of ~50% of the scarps. The added contribution of the longshore energy flux, wave runup and tidal elevation explain 40% of the morphological evolution of beach scarps over the study period.

Pacific Coast of Mexico

Abstract The Pacific coast of Mexico has 68% of the country’s coastline. It comprises several distinct ecoregions and a wide variety of habitats, a great diversity of coastal types and marine diversity, and several endemic or flagship species that live there permanently or transiently. This natural richness offers many opportunities for development and also provides a great challenge for conservation, since the influence of events acting at different scales, including global warming, urban population growth, industrial development, contamination, and overfishing, is evident clearly. The increasing economic activities enhance population growth in some coastal municipalities. Growing urban areas require new resources, magnifying pressures on the environment that manifest themselves through habitat destruction, greater waste production, and soaring pollution. The coasts of the Mexican Pacific are environments vulnerable not only to a variety of natural phenomena but to human activities whose catastrophic effects on natural communities are unequivocally obvious. This review shows that the Mexican Pacific is a region with serious sustainability challenges. A prominent need is to prioritize factors promoting wellness; previously economic growth has been the main and almost only driver without taking into consideration environmental conservations. The need is for diversifying activities that trigger economic growth, reduce socioeconomic inequality, modernize the infrastructure, and improve public security. At the same time, actions to protect critical socio-ecosystems, with the services that they provide, and to conserve the unique biological diversity they support, must be implemented to address the complex challenges that this region of the world is experiencing.