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Coastal dunes that transgress typically move landward, while their reverse movement is not well understood. The article discusses the study of barchan and barchanoid dunes in the Lagoa do Peixe National Park in the coastal plain of Rio Grande do Sul, Brazil. The aim of the study is to analyze seasonal patterns and long-term trends in the direction and migration rates of these dunes, which can pose a threat to the lagoon if they invade its space. The crest migration of 12 dunes was monitored by satellite images between July 2003 and December 2018, and DGPS topographic surveys were performed on five dunes between 2010 and 2018. The migration rates obtained were combined with an analysis of the meteorological data and calculations of the drift potential for eolian sediment transport. The wind regime in the study area shows a multidirectional pattern, with the predominant wind direction being from the NE, followed by the ENE direction. The wind direction also exhibits a seasonal behavior, with the winds from the first quadrant being dominant during spring and summer months and a gradual increase in winds from the second and third quadrants from the end of summer to winter. The dune crest migration rates in the Lagoa do Peixe National Park show an average of 16.55 m·yr−1 towards WSW–W, mainly controlled by the direction of the effective winds. However, intense SSW–WSW winds caused by cold fronts in the past generate the reverse migration of dunes towards ENE–E. The reverse migration of dunes explains the steadiness of the dune fields at CPRGS and is a factor controlling dune stabilization and the geomorphological evolution of transgressive coastal dune fields. The article highlights the importance of monitoring dune movement to understand their responses to natural and anthropogenic stressors and to protect sensitive ecosystems., Conselho Nacional de Desenvolvimento Científico e Tecnológico, Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

Previously, paired spits have been described at the mouths of bays, estuaries, and deltas. This study analyzed the worldwide distribution and morphodynamic patterns of paired spits located at the mouths of interdistributary bays of deltas (three systems) and within coastal channels (24 systems). The methodology was based on the detailed analysis of satellite images, nautical charts, and tidal-range databases. The paired spits found were mainly located on microtidal coasts at high or mid latitudes. Waves were the main factor controlling convergent progradation and breaching of the spits, while the hydraulic blockage for the development of these paired spits was mainly due to tide-induced currents, as well as minor fluvial outlets in the interdistributary bays. Three morphodynamic patterns were identified: (i) stable, with low progradation rates, generally without breaching or degradation of any of the spits; (ii) stationary, with high progradation rates, alternating degradation or breaching of any of the spits with the formation of new spits or closure of the breaches; and (iii) instable or ephemeral, which included three subtypes, the severe erosion of one or both spits, the joining of the head of the two spits forming a single barrier, and the merging of each with its channel margin., Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

We have run a computer simulation of the atmosphere processes and evolution in order to obtain the surface wind field over the ocean. To accomplish this task, we have made use of the mesoescalar open source atmospheric model Weather Research and Forecasting (WRF). The spatial and temporal ranges used for the simulation correspond to the month of November 2007 and the central/north Macaronesia (40N, 20W - 25N, 5W). For an efficient implementation of this simulation in a scenario of rather limited computational resources, it has been necessary to make use of the latest poly architecture distributed computing techniques. Once the wind field has been obtained, we have derived surface currents due to wind stress, Ekman transport and upwelling indices for the whole area, daily and global mean. We have qualitatively and quantitatively compared these results with experimental values derived by other research groups (using remote sensing tools). Finally we have also verified that the results are consistent with those obtained by the numerical model RAMS run for the same space-time conditions described above by the Centre for Mediterranean Environmental Studies (CEAM)., La simulación del campo de vientos superficial en el océano, al noroeste de África, ha sido obtenida usando el modelo mesoescala de código abierto Weather Research and Forecasting (WRF). El rango espacio-temporal elegido para la simulación abarca la región de la Macaronesia central/norte (40º N, 20º W - 25º N, 5º W) durante un mes (noviembre del 2007). Para la ejecución eficiente de esta simulación en un escenario de recursos computacionales limitados ha sido necesario emplear las últimas técnicas en cálculo distribuido poliarquitectónico. Una vez obtenido el campo de vientos, se han derivado las corrientes superficiales debidas al esfuerzo del viento, el transporte de Ekman y los índices de afloramiento para toda la zona, para cada día y en media global. La validación cualitativa y cuantitativa de los resultados obtenidos ha sido realizada comparándola con estudios previos de teledetección realizados por otros grupos de investigación, así como con las simulaciones generadas a partir del modelo atmosférico RAMS. Este modelo ha sido empleado para la mismas condiciones espacio-temporales descritas anteriormente por el Centro de Estudios Ambientales del Mediterráneo (CEAM).

The weathered and fractured conglomerate cliffs of Mont Roig del Camp constitute a rock fall hazard for the surrounding pocket beaches and, therefore, for the population that frequent them, especially over the summer. Landslide susceptibility of the cliff has been assessed using the Rock Engineering System method (RES). The determinant and triggering factors considered in this study include: wave exposure, shoreline variations, cliff height, cliff slope, geotechnical quality of the rocky mass, superficial runoff and cliff orientations favoring landslides. Geographic Information Systems (GIS) have been employed to facilitate the information analysis and generate new susceptibility maps. The quality of the rock mass and cliff orientation are the most interactive factors for the stability of the cliff. However, shoreline variations and surface runoff are the most dominant factors in the system. Thus, the quality of the rock mass has been determined to be a basic variable in the cliff characterization because of its high dependence on the variations of the remaining factors. The landslide susceptibility map depicts a predominance of surfaces with moderate degrees of susceptibility concentrated mainly in the headlands, where the combined actions of subaerial and marine processes control the weathering and eroding processes. Therefore, the landslide susceptibility assessment based on this methodology has allowed the identification of hazardous areas that should be considered in future management plans.