Abstract: In this paper, the most used design aids for beams of rectangular section with parabolic haunches are presented. The beam is found subjected to concentrated load localized anywhere on the beam, and takes into account the bending and shear deformations to obtain the fixed-end moments factors, which is the main contribution of this research work. The first part of this work presents the design aids for the same type of beams to obtain the carry-over factors, the stiffness factors, and the fixed-end moments factors are obtained for a uniformly distributed load. The variables and the simplifications are the same as in the part 1. Also, a numerical example is shown using the design aids, and it is compared with the equations previously presented by the authors in a paper prior to this document, and the results are equal to a three-digit approximation. Therefore, design aids provide a great tool of help for structural engineers by the greatly time-savings.

Resumen: En este trabajo se presentan las ayudas de diseño más utilizadas para vigas de sección rectangular con cartelas parabólicas. La viga se encuentra sujeta a una carga concentrada localizada en cualquier parte de la viga, y toma en cuenta las deformaciones por flexión y cortante para obtener los factores de momentos de empotramiento, que es la principal aportación de este trabajo de investigación. La primera parte de este trabajo presenta las ayudas de diseño para el mismo tipo de vigas para obtener los factores de transporte o arrastre, los factores de rigidez, y los factores de momentos de empotramiento se obtienen para una carga uniformemente distribuida. Las variables y las simplificaciones son las mismas que en la parte 1. Además, se muestra un ejemplo numérico utilizando las ayudas de diseño, y se compara con las ecuaciones previamente descritas por los autores en un artículo anterior a este documento, y los resultados son iguales con una aproximación de tres dígitos. Por lo tanto, las ayudas de diseño proporcionan una gran herramienta de ayuda para los ingenieros estructurales por el gran ahorro de tiempo.

Abstract: In this paper, the most used design aids for beams of rectangular section with parabolic haunches are presented. The variables considered are: the heights at its two ends vary parabolically, the width of the beam is constant, and the height in the central part is constant. The beam is found subjected to a uniformly distributed load, which takes into account the bending and shear deformations to obtain the fixed-end moments factors, the carry-over factors and the stiffness factors, which is the main contribution of this research work. The simplifications are: the heights at its two ends are equal, as these are the most used by aesthetics in architectural constructions, and the total height of the beam in the central part is considered of 0.10 of the length of the beam according to the ACI (American Concrete Institute) code for deflection control. Also, a numerical example is shown using the design aids, and it is compared with the equations previously described by the authors in an article prior to this document, and the results are equal to a three-digit approximation. Therefore, design aids provide a great tool of help for structural engineers by the greatly time-savings.

Resumen: En este trabajo se presentan las ayudas al diseño más utilizadas para vigas de sección rectangular con cartelas parabólicas. Las variables consideradas son: las alturas en sus dos extremos varían de forma parabólica, el ancho de la viga es constante y la altura en la parte central es constante. La viga se encuentra sometida a una carga uniformemente distribuida, que toma en cuenta las deformaciones por flexión y cortante para obtener los factores de momentos de empotramiento, los factores de transporte o arrastre y los factores de rigidez, que es la principal aportación de este trabajo de investigación. Las simplificaciones son: las alturas en sus dos extremos son iguales, por ser estas las más utilizadas por la estética en las construcciones arquitectónicas, y la altura total de la viga en la parte central se considera de 0.10 de la longitud de la viga según el código ACI (Instituto Americano del Concreto) para el control de deflexión. Además, se muestra un ejemplo numérico utilizando las ayudas de diseño, y se compara con las ecuaciones previamente descritas por los autores en un artículo anterior a este documento, y los resultados son iguales con una aproximación de tres dígitos. Por lo tanto, las ayudas de diseño proporcionan una gran herramienta de ayuda para los ingenieros estructurales por el gran ahorro de tiempo.

ABSTRACT This paper present other part of the extensive experimental campaign by physical model in order to obtain an effective solution to reduce the wave overtopping in the Malecón traditional. It was determined the wave overtopping rate for the current situation and for two typologies of seawalls and seawalls combined with berms. It presents a comparative study, taking into account the alternative fulfill the admissible rate of 50 L/ms as project restriction. The testes confirm that the combination of the seawall and berm has the best results for the wave and water level studies conditions, and for the technical restrictions.

RESUMEN Se presenta otra parte de una campaña experimental usando modelación física para obtener una solución efectiva en la reducción del sobrepaso del oleaje en el Malecón Tradicional de La Habana. Se determinó la tasa media de sobrepaso para la situación actual y para otras tipologías de muro y muros combinados con berma. La evaluación de las alternativas fue llevada a cabo mediante un análisis comparativo, considerando la reducción la tasa media de rebase, así como observando cuál de estas cumple con la tasa media de descarga de 50 L/sm. Esto confirmó que las variantes que combinan el muro curvo con las bermas generan los mejores resultados para las condiciones estudiadas de clima marítimo y las restricciones técnicas impuestas.

ABSTRACT It present the stability studies for different coastal structures obtained by physical model studies. It was done at the Laboratorio di Ingeneria Costiera (LabLInc) of the Department of Civil, Architectural and Environmental Engineering (DICEA) of the University of Naples Federico II, It was done a preliminary study using rock to form the armour of the breakwater, as result the failure of the structure was verified. A new design was done for a low crest of breakwaters and berms, using concrete cubes for the armour. The tests results demonstrated that the berms failed for the higher wave heights. For breakwaters the failure is associated with the location at breaking zone, it is recommend to apply an concrete element with more interconnection, and pay attention to the toe protection of the structures.

RESUMEN Se presentan los estudios de estabilidad realizados en modelo físico a estructuras de defensa costeras obtenidas de una amplia campaña experimental para definir la solución de defensa costera del Malecón Tradicional de La Habana. Se realizó un estudio preliminar a rompeolas conformada su coraza con rocas, como resultado se comprobó el fallo de la estructura. Se llevó a cabo el rediseño de los rompeolas de baja cresta y bermas emergidas utilizando como elementos para la coraza cubos de hormigón. Como resultado de las pruebas las bermas emergidas fallan para los mayores oleajes. En el caso de los rompeolas su fallo está asociado a la localización en la zona de rompiente. Se recomienda aplicar un elemento de mayor interconexión, y prestar atención a la protección del pie de las estructuras.

El propósito fue identificar las características fisicoquímicas del material que constituye el depósito tipo playa, para lo cual se desarrollaron tres fases en el proceso de investigación: (a) Campo: colecta de sedimentos superficiales en la berma, mediante una transecta longitudinal y sobre esta, cada 20 metros, transectas trasversales hacia las zonas del vaivén y el rompiente, para un total de 45 muestras; (b) Laboratorio: análisis físico (granulometría y morfología de los granos) y químico (contenido de CaCO ), y (c) oficina o de procesamiento estadístico. El depósito está constituido por partículas de la talla de las arenas medias a gruesas, moderadamente seleccionadas y leptocúrticas, morfológicamente angulosos, con un porcentaje de CaCO que varía según la posición. El material, tiene una fuente de origen predominantemente en las rocas metamórficas del Macizo del Ávila siendo trasportados hacia su posición actual por el río Limón.

The purpose was identify the physicochemical characteristics of the material constituting the beach depot, to do field research is assumed, developed in three stages: (a) Field, allowing the collection of surface sediments into the berms by a longitudinal transect and this at 20 m, manner transverse to the reciprocating parts of the surf zone and to a total of 45 samples; (b)Laboratory physical and chemical analysis (particle size and morphology of the grains) and (CaCO content), and (c) office or statistical processing. It is recognized that the deposit consists of particles of the size of the medium sands to coarse, moderately sorted and leptokurtic, morphologically angular, with a percentage of CaCO that varies with the position. It is concluded that the material has a source of origin in metamorphic rocks that limits south, being transported to its current location by Limón River.

Excessive anthropic occupation reduces the coastal extension and causes significant impacts on the ecosystem. Urban evolution in coastal areas has reached a point of no return. For this reason, the knowledge about whether a particular type of infrastructure or vegetation on a frontal dune could cause greater or lesser impact on the beach is extremely useful for urban planning. The study area was Pehuen Co (Fig. 1), a town located in the southwest of the Buenos Aires Province (Argentina). The aim of this work is to analyze the evolution of beach profiles backed with different foredune cover in order to understand the erosion/accretion processes that may be related to the various dynamic conditions. This will provide useful information to decision makers for urban planning and sustainable management projects orientated for short, medium and long terms. Pehuen Co is a dissipative beach with east-west coastal orientation within a region with alternating wet and dry periods. Normally, rains are concentrated in spring-summer, decreasing in autumn and becoming minimal in winter. The prevailing winds are from N and NW, with greater intensity in the spring and summer, mainly December and January. The study area coincides with the smaller beach of the downtown sector (Fig. 2). To the west, the foredune has been heavily eroded and has a steep front, whereas to the east there are vegetated, large dunes. The dominant vegetation is Tamarix gallica and Carpobrotus edulis, which are not observed in the walkways to the beach or where there are infrastructures over the foredunes. Beach profiles in different geomorphological situations were analyzed in order to describe their behavior. Three different sectors separated 50 m from each other were selected: ZC1 next to a restaurant on top of the frontal dune, ZC2 on the vegetated dune, and ZC3 on a walkway to the beach (Fig. 2). Monthly beach profiles were carried out from July 2007 to June 2010. The profiles were made using a modified version of the method proposed by Emery (1961), already developed in Bustos et al. (2013). The analysis of the beach profiles was performed seasonally (summer, autumn, winter and spring). Additionally, others were surveyed after strong storms. The profiles were digitalized and the volumes for the sediment budget and the Annual Variation Rate (AVR) were calculated. The volume was calculated considering a constant beach width equal to 1 m and a length defined by the shorter profile. Principal Component Analysis (PCA) was applied to complete the analysis of the seasonal beach profiles. The study for all sectors demonstrated that during winter periods they all present concave profiles (Fig. 3), while during the summer periods were characterized by significant berms (Table 1). The profiles at ZC1 and ZC2 behaved rather similarly, whereas those at ZC3 were still more concave than the others. ZC3 during the winter of 2009 presented a 1.5 m microcliff on the dune front. Also, during the summer profiles showed areas of accumulation, mainly with the formation of berms and bars (Fig. 3). The sedimentary balance reflected the behavior of the profiles, with volume increment in the summer periods and reduction in winter (Fig. 4). ZC1 presented a negative balance with an erosional trend. ZC3 profiles had the highest losses, with up to 60 m³ of erosion in the winter of 2008. The TVA for both profiles were negative, for ZC1 it was -12.9 m³/ yr, and for ZC3 of -20.3 m³/yr. In contrast, ZC2 had a positive TVA (9.9 m³/yr). Its largest gain occurred in Autumn 2009 (65.6 m³) (Fig. 4). ZC3 showed more concave profiles than the rest and represents the place with higher sediment loss, especially during rainfall. The entrances to the beach are constructed perpendicularly to the coast and without vegetation protection. For this reason, they are easily eroded, mainly by rainwater runoff. Monthly characteristics and trends in the behavior of the beach profiles were obtained by applying a PCA. The average profile of ZC1 presented a stable line with a slight concave tendency. Sediment loss was mainly observed in summer, winter and autumn; accretion occurred in spring (Fig. 5). The ZC2 profile showed a slightly concave shape, similar to ZC1, while small erosion cycles were observed every three months. The average profile showed losses in winter, spring and autumn, whereas it only gained sediment in summer (Fig. 6). The average profile in ZC3 is more concave than ZC1 and ZC2. The temporal components showed an erosion trend, with cycles of approximately six months of accretion-erosion. During autumn, winter and spring the sediment of the average profile decreased while increased in the summer (Fig. 7). In order to evaluate the damages and response of the beach profiles to erosive events, the impact of a wind storm that occurred between 22 and 23 July is presented as an example. This event on the beaches of Pehuen Co was originated due to an extensive frontal storm. The winds associated with the front prevailed from the south with a maximum intensity of 63.7 km h-1. The total length of the event was approximately 33 h. The waves on the beach, favored by the strong wind, reached 5 m in height (based on SMN map data). Beach profiles were made before and after the event to estimate volumetric differences. The effects on the beach and buildings were analyzed by field recognition after the event. Based on the profile data, we observed an erosive behavior with the profile becoming concave. ZC1 had a total volume loss of 3.17 m³, specifically on the backshore. The rest of the beach remained basically constant. The erosion caused damage to the infrastructures over the dune. In September (2009) the profile had recovered 2.38 m³ with respect to the pre-storm profile. The ZC2 had a behavior similar to ZC1 in terms of sediment loss and gain. A volume of -9.16 m³ was lost. In September, a sediment recovery from the pre-storm profile of 9.04 m³ was observed (Fig. 8). ZC3 had significant erosion in the dune area, with an escarpment of 1.6 m high. In this zone of the backshore, a volume loss of 6.51 m³ was recorded between the pre- and post-storm profiles. In September, this profile did not recover as in the other two sites (ZC1 and ZC2). The escarpment began to diminish in height on December, four months after the storm occurred (Fig. 8). The ability to differentiate the behavior of the beach according to the coverage of its frontal dune is fundamental for land-use planning. Therefore, to find solutions applicable in the short and medium term is important to the natural balance, economic and social growth of these cities. It is concluded that in an erosive zone such as the central area of Pehuen Co, the frontal dune cover is decisive for coastal dynamics. The impact and recovery of the beach after storm events were better developed in places with vegetation cover over the dunes. In turn, the beach profiles in areas with perpendicular entrances to the beach had strong erosion processes and slow recovery. We recommend to modify the entrances to the beach and reduce their number as much as possible. Therefore, risk maps are needed in order to generate better planning for coastal urban development.

Los asentamientos urbanos ocasionan una degradación de las playas haciéndolas más vulnerables a los efectos de eventos naturales (olas, mareas, vientos). Por este motivo, conocer el impacto del tipo de infraestructura o vegetación en médanos frontales puede ocasionar en la playa resulta de suma utilidad para la planificación urbana. En la localidad de Pehuen Co, al sudoeste de la provincia de Buenos Aires (Argentina), se analizó la evolución de un sector específico de la playa con diferentes coberturas del médano frontal para comprender su comportamiento general (erosión y/o acreción). Para ello, se realizaron perfiles de playa mensuales y luego de tormentas fuertes, desde julio de 2007 a junio de 2010. Se eligieron tres sectores diferentes, separados 50 m entre sí, para realizar los perfiles: 1) al lado de una edificación construida sobre el médano frontal, 2) sobre el pie del médano vegetado, y 3) sobre una bajada peatonal hacia la playa. Sobre los resultados se aplicó un Análisis de Componentes Principales (ACP) y se calcularon los volúmenes sedimentarios. Con el fin de completar el análisis se creó una matriz de doble entrada que permitió observar los desplazamientos y comportamientos de las geoformas en cada perfil. Finalmente, para evaluar los daños y respuesta en los perfiles de playa ante eventos erosivos se evaluó el impacto de uno de los temporales de viento más fuertes del período. Se concluyó que la cobertura del médano frontal es decisiva para la dinámica litoral. El impacto y la recuperación de la playa luego de eventos de tormenta fueron mejores donde había coberturas con vegetación. A su vez, los perfiles de playa en zonas con bajadas a la playa perpendiculares a la misma tuvieron fuertes procesos erosivos y lenta recuperación de sedimentos. Las diferentes respuestas de la playa según las condiciones que posee el médano frontal serán de ayuda a quienes deben tomar decisiones al momento de planificar la urbanización y emprendimientos a corto, medio y largo plazo sobre la franja costera.

O balneário Hermenegildo está localizado no extremo sul do Brasil, no município de Santa Vitória do Palmar. Esta praia vem sofrendo um significativo processo de erosão costeira, danificando propriedades situadas à beira mar, fato que vem sendo combatido pelos próprios moradores através da colocação de estruturas de contenção à erosão. Este trabalho tem como objetivo analisar se essas estruturas de contenção dispostas na orla do balneário Hermenegildo estão realmente contendo a erosão costeira e, além disso, qual seu impacto sobre as características da praia nesse trecho. Para isso, foi utilizado um GPS geodésico em módulo de posicionamento relativo cinemático em tempo real (Real Time Kinematic - RTK) para mapear linhas de referência: linhas de dunas na parte urbanizada e junto às dunas frontais nas porções sul e norte do balneário, linha d’água ao longo do mesmo trecho e perfis topográficos transversais à costa. Esses dados foram corroborados por outras ferramentas de análise, tais como imagens aéreas, mosaicos de fotografias convencionais e identificação das estruturas de contenção, utilização de um sistema de informações geográficas (SIG), além da própria revisão bibliográfica. Ao analisar as diferenças encontradas entre a posição da linha da base das escarpas na parte urbanizada (zona estruturada) e a linha da base das dunas frontais adjacentes ao norte e ao sul do balneário, foi detectado que parte considerável da orla urbanizada está sobre a pós-praia, com uma área de contenção calculada em 54.100m² no ano da medição. Especificamente a porção central da orla urbanizada, onde existe maior concentração de estruturas de contenção mais resistentes à erosão costeira (como enrocamentos), está mais projetada sobre a face da praia em relação às áreas adjacentes. Com isso, conclui-se que as estruturas de contenção no balneário, mesmo que colocadas pelos próprios moradores, muitas vezes sem um conhecimento adequado de obras de engenharia costeira, estão contendo, pelo menos parcialmente, a migração horizontal da linha de costa em direção ao continente, embora muitas casas já tenham sido destruídas nos últimos 50 anos e substituídas por áreas de praia. Por outro lado, essa fixação da mobilidade horizontal da linha de costa acarreta impactos na morfologia praial na parte que está mais impactada pelas estruturas, como diminuição da largura da praia, ausência de bermas, o que diminui a declividade na face da praia, e presença de escarpas íngremes no limite superior, entre a praia e a área urbana. Durante a medição realizada, a linha d’água apresentou uma concavidade em frente ao setor central, o que indica que ocorre uma retirada de sedimentos nas áreas junto às estruturas de contenção. Tal característica apresenta-se bastante dinâmica espaço-temporalmente e necessita ser mais bem analisada. Com o progressivo avanço marinho sobre uma área urbana projetada sobre a praia, com progressiva diminuição entre a linha de quebra de ondas e as estruturas de contenção e área urbanizada, torna-se apropriado refletir sobre estratégias de contenção à erosão para médio e longo prazo, com um efetivo planejamento territorial e ambiental.

Hermenegildo beach, located in Santa Vitória do Palmar, Rio Grande do Sul state, in the extreme south of Brazil (fig.1), has been undergoing a significant problem of coastal erosion that started at the end of the 50’s and has gotten worse since the 90’s. It has damaged seashore properties whose owners have faced this situation by armoring their properties with containment structures against the erosion (fig.2). This study aimed at analyzing whether the containment structures along Hermenegildo beach have actually hold coastal erosion and what impact they have on the characteristics of this stretch of beach. In order to carry it out, a geodesic GPS in real time kinematic (RTK) mode was used to map the so-called reference lines: all the upper limit of the beach in the urbanized part (limit of slopes and containment structures on the beach) and the upper limit of the beach along the frontal dunes in the south and the north of the urban area (the basis of the frontal dunes) on a coastal stretch that is about 5 km long; the high waterline along the same stretch (fig.5); an interpolated line was done linking linear regression made with the GPS points from foredunes from north and south of the urbanized part (fig.6). Additionally, 22 topographic profiles which are transversal to the beach were mapped, in order to investigate the morphological differences of the slopes found in this study (fig.7). These data were supported by data collected by other tools, such as aerial images, mosaics of conventional photographs and the identification of containment structures, the use of a Geographic Information System (GIS) and by the literature review itself. Points marked by the GPS in sectors called North Dunes and South Dunes have shown that the upper limit of the beach with these dunes has a relatively straight conformation on the map, similar to what is expected from a natural environment in that place (where most beaches are quite straight or oblong, except for washout channels which generate little recesses). However, the Urbanized Shore sector has a very irregular upper limit on the beach due to different shapes of containment structures or even to their absence on this stretch. The analysis of the differences found between the upper limit of the beach in the urbanized part (structured zone) and the one close to the frontal dunes in the south and the north of the urban area showed that the central part of the urbanized shore - where there is the largest number of containment structures, such as rockfill, which are more resistant to coastal erosion - advances over the shoreline, by comparison with the adjacent areas, and comprises a containment area of 54,100m² in the period under analysis (fig.8). The longest distance between the Urbanized Shore sector and the interpolated dune line was 45.3 meters (fig.8, ‘M’). Therefore, this study concluded that the containment structures on the beach, even though they were built by dwellers that did not have specific knowledge about coastal engineering, have hold, at least partially, the horizontal migration of the shoreline towards the landside, although several houses have already been destroyed and replaced by beach areas over the past 50 years. It must be highlighted that the authors of this study do not stimulate this kind of construction in other urbanized coasts. However, there is evidence that the protection structures, such as rockfill, have been efficient in Hermenegildo since they held the erosive process in that place, at least in the period under investigation. On the other hand, fixing the horizontal mobility of the coastline leads to significant impacts on the beach environment, mainly in the morphology of the part that has been more affected by the structures. Impacts comprise the decrease in the beach width, no berms - a fact that diminishes the declivity on the beach face - and steep slopes on the upper limit of the beach (fig.9); thus, it gets harder to gain access to the beach. During the measurement, the waterline had a concavity in front of the central area (fig.8); it means that sediment has been removed from the areas close to the containment structures and that they interfere with the sediment balance in the horizontal plane besides generating vertical sediment deficit. Such concavity seems to be quite dynamic in terms of space and time; thus, a deeper analysis is needed. The short distance from the coast to the waterline (fig.8, ‘m’) was related to the projection of the containment structures and the concavity of the waterline. The beach area is very small, not only for the dissipation of the wave energy but also for the users’ leisure, i. e., the natural shore has been thoroughly suppressed, a situation that is not considered adequate to that place. In addition, since there is progressive advance of the sea over the projected area and progressive reduction between the swash zone and the containment structures in the urbanized area, it is not known how long these structures are going to keep protecting the urban area. Therefore, it is necessary to reflect on long-term management strategies along with effective environmental planning to account for future constructions. Regarding the material and methods employed in the study, it is worth mentioning that the GPS-RTK is a very efficient and precise tool which enables researchers to collect numerous data quickly. In fact, all positioning data - that referred to the GPS - used in this study could be collected on one day in situ. Even though errors may occur, they can be considerably mitigated.

From august 2007 to june 2009, ten topographic profiles were made on the Carrizal beach during rainy and dry seasons in order to determine the morphologic changes on beach profiles. Samples of sediments were collected in nearshore, onshore and backshore related to the beach profiles. The results show that the morphology of the beach zone near the mouth of the lagoon of Coyuca is more dynamic with high berms to 2 meters, strong slopes from 10 to 15 degrees and beaches are less than 45 meters in width. A major stability is finding in the farthest part of the lagoons mouth where profiles are accumulative and longger than 50 meters with soft slopes. The sediments are composed of quartz-pheldespatic sands, usually of medium size, well sorted and skewed to coarse sands and they are leptocurtic in beach face and in backshore, while in the nearshore they are skewed to coarse sizes.

De agosto del 2007 a junio del 2009, se llevaron a cabo 10 perfiles topográficos en playa Carrizal durante las épocas de lluvias y estiaje de estos años para determinar el cambio morfológico de la playa. Paralelamente se realizó un muestreo de sedimentos en la infraplaya, mesoplaya y supraplaya asociados con estos perfiles de playa. Los resultados muestran los mayores cambios morfológicos de la playa en la zona aledaña a la boca de la laguna de Coyuca con escalones de erosión en las bermas de mareas de hasta 2 m de altura y playas menores que 45 m de amplitud. Una mayor estabilidad se tiene en la parte de la playa más alejada de la boca lagunar con perfiles acumulativos de más de 50 m de amplitud y pendientes suaves. Los sedimentos son arenas cuarzofeldespáticas con predominio de arenas medias, bien clasificadas, asimétricas hacia tamaños gruesos, leptocúrticas tanto en la zona de mesoplaya como en la supraplaya, con la presencia de arenas gruesas en la infraplaya.

Our ability to predict beach erosion above the still water level (SWL) is still not satisfactory due to the lack of adequate technology to accurately measure the sediment concentration and velocity in very shallow water, including the swash zone where the beach face is intermittently covered with water and exposed to the atmosphere. A simple procedure is proposed here to improve our predictive capability for the particular case of scarping erosion caused by wind-generated waves above the SWL. If the slope at the steep scarp is larger than the limiting slope of the internal sediment friction, the steep face is assumed to be eroded due to the computed offshore sediment transport at the toe of the scarp. The bedload and suspended sediment transport at the toe of the scarp was computed using a time-averaged model that includes the steep bottom slope effect. The model was validated against a novel experiment in a multidirectional wave basin, where scarping was reproduced. The water level was raised in four steps to reproduce the shoreface erosion, berm overwash and berm erosion, successively. Horizontal and tilted berms were tested against similar normal incident irregular waves to compare the performance of the profile without and with ponding, respectively. For the tilted case, ponding appeared when the tilted berm was overtopped. No ponding was observed for the horizontal berm test even when the berm was overtopped. The predictability was estimated using the Brier skill score (BSS). The predictability of the scarping was good (BSS ≥ 0.6) for the horizontal berm test and fair (BSS ≥ 0.4) for the tilted berm test. This decrease in the predictability may be related to the ponding, which is not included in the model.

Nuestra capacidad de predecir la erosión de la playa por encima del nivel medio del mar en reposo se encuentra todavía en desarrollo. Esto es principalmente debido a la falta de tecnología que permita medir con la precisión necesaria la concentración de sedimentos y la velocidad del flujo en aguas poco profundas, incluyendo la zona de swash que es intermitentemente sumergida y expuesta a la atmósfera. En un intento de mejorar nuestra capacidad de predicción, se propone un modelo sencillo para el caso particular de la formación de escarpe por encima del nivel medio del mar en reposo debido al ataque del oleaje generado por el viento. Si la pendiente del escarpe es superior a la pendiente de equilibrio del sedimento, la tasa de erosión del frente de arena se supone igual a la erosión estimada al pie del escarpe. El transporte de fondo y en suspensión al pie del escarpe es calculado empleando un modelo promediado en el tiempo al que se ha incluido el efecto de la pendiente del fondo sobre el transporte. El modelo es validado con un experimento en un tanque multidireccional de oleaje, donde se reprodujo la formación del escarpe. El nivel del agua en el tanque se elevó en cuatro pasos para reproducir la erosión del frente de playa, el rebosamiento y la erosión de la berma sucesivamente. Las bermas horizontal e inclinada hacia tierra se sometieron a oleajes irregulares similares de incidencia normal para examinar la influencia de la acumulación de agua tras la berma sobre la evolución del perfil de playa. En el caso de la berma inclinada se observó una acumulación esporádica de agua tras la cresta de la berma cuando ésta era rebasada. No se observó acumulación de agua tras la berma horizontal. La capacidad predictiva del modelo fue estimada en base a la escala de Brier (BSS por sus siglas en inglés), resultando buena (BSS ≥ 0.6) para el caso de la berma horizontal y justa (BSS ≥ 0.4) para el caso de la berma inclinada. Esta disminución en la predictibilidad puede estar relacionada con el rebosamiento sobre la berma, el cual no ha sido considerado en el modelo.

The behaviour of the acumulation of dead leaves of Posidonia oceanica (vegetal berm) over the backshore has been analized. Two beach profiles, before and after its mecanical elimination, were made. After that, SW a stormy episody took place, giving as a consequence the erosion of both backshore and foredune, due to the elimination of the vegetal berm. The final result was a loss of beach and foredune surface.

Se ha analizado el comportamiento del perfil de una playa natural con acumulación de hojas muertas de Posidonia oceanica (berma vegetal) ante la actuación de maquinaria de limpieza. Se realizaron dos perfiles, uno anterior a la retirada mecánica de la berma, y otro posterior a ésta, coincidiendo con un episodio de temporal de SW que incidió de forma directa sobre la playa desprotegida de la berma. El resultado obtenido fue una pérdida de superficie de playa y foredune.

The effects on the dynamics, morphology and texture of the beaches between Miramar and Nutria Mansa creek produced by beach mining activities in a sand pit located 2 km southwards from Centinela del Mar were analyzed. Also the beach recovery since the end of the sand exploitation in July 1997 was evaluated for mining area and for the case studied: Mar del Sur. The mining activity affected an area of 200.000 m2, with an extension of 1.800 m along the coast, with a sand volume estimated in 150.000 m3. The sand was mainly extracted from the berms and foreshore. A rapid increased in the coastal retreat has been detected for all the localities studied since 1984 in coincidence with the beginning of the mining activities on the beach. Otherwise the backward movements rates of the coastline decrease with the proxioity to the mining site. A decrease in mean grain-size and an increase in standard deviation was observed from the comparisson of grain-size analysis performed in 1956 and 1998. It indicated an increase of the erosive power of littoral currents during this period. An increase in the positive skewness was also detected in the foreshore during the same period. The morphologic studies, the grain size analysis and field observations showed that the sand mining generated an erosive wave which was moving northward in the direction of the littoral currents. The sand exploitation from the beach produced a decrease in the littoral current saturation favoring the degradation of the beach sand deposits and increasing cliff retreat, mainly of those carved over dunes. Several morphologic evidences indicated active erosion: - Wave cut platforms with no sand cover where ancient beaches were described. - Active scarp formation in present foredunes. - Isolated dune relicts on the beach. - Displacement of the intertidal beach to the seafront housing area. - Roads cut by active cliffs. The beach recovery induced by the sand mining after closure of the mining activities was studied considering the case type at Mar del Sur. An accumulative sedimentary budget, was recorded in the exploitation area for all the profiles, after a year of the interruption of the mining activities on the beach along 900 m. The budgets obtained from northeast to southwest are: profile 1: none, profile 2: 25,94 m2/m, profile 3: 41,69 m2/m, profile 4: 21,00 m2/m, profile 5: 18,59 m2/m. A net accumulation of 23.300 m3 was estimated. An annual negative budget of -554 m3 at Mar del Sur beach was detected after the interruption of the sand mining activities in July 1997. An accumulative sector located in the middle of the bay was observed with a positive budgets of 3.176 m3 as well as an erosive zone at the north with a negative budget of -3261 m3. Near the groin a small erosive zone was observed with a negative sedimentary balance of -486m3. The total budget of the bay is neutral (-68 m3) if the erosive effect of the groin is discarded. The comparison of the annual budget obtained by other authors, the morphologic features of the coast and the accumulation budgets registered in the middle of the bay may imply that the beach erosion was attenuated after the closure of explotation.

Se investigó el efecto producido por la extracción de arena de playa de la cantera ubicada 2 km al suroeste de Centinela del Mar (partido de Lobería) sobre la dinámica, morfología y textura de las playas localizadas entre Miramar y el Arroyo Nutria Mansa. Asimismo, se evaluó el efecto de la recuperación de las playas en la zona de extracción y en sectores aledaños (caso tipo: Mar del Sur), luego del cese de las tareas de explotación en junio de 1997. La actividad minera afectó una extensión de 1.800 m de playa, sobre una superficie de 200.000 m2 y un volumen estimado en 150.000 m3 de arena. Las tareas de extracción minera se realizaban principalmente de los sectores de berma y playa frontal y abarcaban un extensión de 900 m a lo largo de la línea de ribera. Se detectó un incremento brusco en la velocidad de retroceso de la costa durante el período 1984-1997, en todas las localidades monitoreadas, en concordancia con el inicio de las actividades mineras en la playa en el año 1988. Por otro lado estas velocidades de retroceso aumentan hacia el sitio de extracción. Los análisis texturales comparativos entre los años 1981 y 1998, han evidenciado un incremento en el tamaño de grano y en la desviación estándar (peor selección), lo cual estaría indicando un aumento en las condiciones erosivas. La asimetría ha presentado valores más positivos en la playa frontal. Los análisis morfológicos, texturales y las observaciones de campo demuestran que la explotación del yacimiento generó una onda erosiva que se desplaza hacia el noreste en el sentido de la deriva litoral. El efecto de la explotación produjo una disminución en la saturación de las corrientes litorales favoreciendo en consecuencia la degradación de los depósitos arenosos e incrementando la velocidad de retroceso de los acantilados, en especial de aquellos friables como las costas de dunas. Las evidencias morfológicas que corroboran este hecho son: el hallazgo de numerosas plataformas de abrasión desprovistas en su totalidad de sedimentos arenosos en sectores donde antiguamente existían depósitos de playa, formación de escarpas en dunas actuales, remanentes de dunas aislados en sectores de playa, cortes de senderos vecinales por acantilados activos y extensión de la actual zona intermareal hacia sectores con edificaciones que antes quedaban fuera de su influencia. La evaluación efectuada luego de un año del cese de las actividades de explotación de la cantera en el área de extracción ha dado como resultado un balance sedimentario positivo (acumulación), a lo largo de los 900 m de playa que ocupaba la muesca de extracción. Las tasas sedimentarias registradas de noreste a suroeste respectivamente son las siguientes: perfil 1: neutro, perfil 2: 25,94 m2/m, perfil 3: 41,69 m2/m, perfil 4: 21,00 m2/m, perfil 5: 18,59 m2/m. Se estimó una acumulación neta de 23.300 m3. La recuperación de las playas aledañas al sector de mayor erosión fue estudiada tomando como caso tipo las playas de Mar del Sur. Se detectó un balance anual levemente negativo (-554 m3) para Mar del Sur luego del cese de las actividades mineras, con un sector de acumulación localizado en el centro de la bahía (+3.176 m3), un sector erosivo al noreste (-3.261 m3) y con un balance negativo de menor magnitud asignado, por las variaciones morfológicas registradas, al efecto del espigón (-486 m3). Si se descarta la influencia de la estructura el balance total es prácticamente neutro (-68m3). La comparación con balances anuales determinados por otros autores (Isla et al., 1997), las características morfológicas de la costa de Mar del Sur, y la acreción registrada principalmente en el centro de la bahía, podrían indicar que la erosión ha sido levemente atenuada luego del cese de la explotación. La construcción de un espigón en el último año, generó una alteración muy localizada sobre una superficie de 5.000 m2 y se considera que no afectó significativamente el balance sedimentario total calculado para Mar del Sur. Se sugieren recomendaciones para minimizar el impacto ambiental generado por las tareas de explotación.

The beaches of Villa Gesell have suffered important rates of erosion related to antrhopogenic activities which altered the natural coastal ecosystem. The man induced erosion was mainly recognized on the beaches located in the center of the town. A morphodynamic model that shows the beach configuration response to man induced erosion and seasonal variations is proposed in the paper. Three stages of man induced erosion were described: high, moderate and low .The model is useful to detect low rates of erosion based on the monitoring of the stable berm and transitional berms behavior in the beach profile. The coastal area of Buenos Aires is represented by an accumulative coast characterized by an active dune field of 0.05 km to 3.5 km width with dunes height that vary between 2 to 25 m. The beaches are 60 m to 140 m width and present slopes below 2°. They are composed of medium to fine sand. The beach profiles show seasonal changes. It was observed that only one berm is stable and is the most sensitive parameter to evaluate the natural recover to erosion. It is preserved during storm erosion episodes and is recovered naturally except in those sectors where the beach is affected by urbanization. Two or more berms attach to the stable berm in winter and disappear in summer during a year cycle. This reflects the natural evolution of the beach profile under natural conditions. In urbanized areas, the transitional berms disappear and the stable berm is cut by scarps during surge storms. The stable berm has higher altitudes and width (30-40 m), than the seasonal berms (20-25 m). The mean grain-size of the stable berm varies from 1.10 to 1.88 phi and the sorting between 0.56 to 1.28. Grain-size diminished from summer to winter while the sorting increased. The backshore between the stable berm crest and the foredune also suffers seasonal changes. During winter the slope is reduced. The natural recovery is related to the supply of sand from the dune. In sectors where the dune was destroyed by urbanization the profile can not be naturally recovered resulting in erosion of the backshore. Textural analysis of beach sediments from different subenvironments were analyzed as well as their relation with: temporal variations in a mesoscale (seasonal changes), spatial changes along the coast and across the beach profile and human-induced erosion. Mean grain-size, phi standard deviation and skewness were adequate parameters to identify man-induced erosional processes in the foreshore of the city of Villa Gesell. An increase in the standard deviation, a coarser grain size and a trend to a negative skewness characterised the beach sectors affected by erosional processes. Diagrams comparing skewness and standard deviation representations were useful tools to discriminate shore erosion. It was observed a positive linear regression for erosional beaches and a negative regression for natural beaches. The univariate entropy analysis was used because it can treat a complex grain size distribution as readily a simple one and does not ignore limitation such as normality of distribution. The comparison of the results are quite well correlated with the standard deviation. The standard deviation and the relative entropy analysis of the foreshore sediments mainly represent the seasonal changes. During summer the standard deviation decreases while during winter it increases in response to the incoming of seasonal berms with higher contents of shells. The presence, location, and morphological conservation of the stable berm during a year cycle is proposed to be used as a field indicator to determine the beach vulnerability to erosion.

Las playas de la localidad de Villa Gesell han sufrido un importante grado de erosión relacionado con un mal manejo del ecosistema costero y con un incremento explosivo en la población turística. Se presenta un modelo de variación morfodinámico estacional en playas afectadas por distintos grados de alteración antrópica al medio físico, reconociéndose tres estados de erosión inducida: bajo, mediano, alto. Se determinó un ciclo de recuperación anual para playas naturales, con cambios en la configuración del perfil de playa relacionados a la disposición y presencia de bermas estacionales durante el invierno. En áreas urbanas se detectó una alteración en los ciclos naturales de recuperación. Las bermas estables pueden estar o no presentes en función del grado de deterioro del equilibrio natural. En sectores fuertemente afectados por la urbanización, la berma estable desaparece y pasa a integrar bermas estacionales acíclicas. Si el grado de alteración es separación se mantiene una berma estable que es parcialmente erosionada durante un ciclo anual y pueden o no adosarse bermas transicionales durante el invierno. Asimismo se analizan los parámetros texturales de los sedimentos de los distintos subambientes de playa y su relación con las variaciones temporales en una mesoescala (cambios estacionales) y su relación espacial (variaciones a lo largo de la costa). La playa frontal, es el subambiente que mejor refleja las variaciones temporales y espaciales, debido a la gran influencia de la alternancia entre el lavado y deslizamiento producidos por la acción combinada de las mareas y del oleaje. Los parámetros texturales que evidenciaron una mejor respuesta a las condiciones erosivas son la asimetría, la selección y la media en la playa frontal. Mientras que los parámetros físicos determinantes son disminución en el ancho de playa e incremento en la pendiente. Otro factor textural determinativo es la combinación entre selección y asimetría en los diagramas bivariantes. En playas erosivas, al incrementarse la desviación estándar disminuye la asimetría y en playas naturales la relación es inversa. El análisis univariante de la entropía en los sedimentos de playa frontal puede considerarse como una alternativa apropiada para determinar la selección, aunque en las playas estudiadas la última resalta mejor la selectividad del medio de transporte. La selección y entropía son los únicos parámetros texturales determinativos de las variaciones estacionales. Se detectó una disminución en la desviación estándar y de la entropía durante el verano en las muestras analizadas.

Observations in a mangrove lined coast in south-western Puerto Rico (rainfall 800-1,000 mm; evaporation 1,900-2,200 mm; mean annual temperature 25º C; and average tidal range 0.3 m) have shown that the degree of structural development of the mangrove forest is closely related to wave exposure. In exposed coastal segments, sand berms formed by wave action within the outer fringe prevent water flow towards the inner forest, resulting in high salinities. The berms are higher in areas where the outer mangrove fringe has been destroyed by storms or other causes. Dead mangrove stands are found behind these areas and salinities reach 75-80‰ We suggest that the mangrove fringe contributes to dissipate wave energy over a broad area which reduces the high of the berm. The presence of absence of "blowholes" in the seagrass Thalassia; bed is an index of the degree of protection that the coast receives. The "thickness" of the mangrove fringe is also related to the degree of shelter: it is "thin" in high energy segments, "thick" in coastal segments subject to intermediate energy and "thin"again in the most sheltered locations. In the outlying cays mangrove development follows a similar pattern: the outer exposed cays (essentially coral islands mantled by coarse sands) are devoid of mangrove cover or have stunted trees (generally Laguncularia; canopy height, 2 m). Islands which are less exposed are colonized by Rhizophora which frequently forms overwashed forests (canopy height, 8-9 m). In the most seltered areas, Rhizophora colonizes the shallow banks, forming islands which soon develop an inner hypersaline lagoon due to the accumulation of material in the outer edges and the accumulation of salt in the interior. The wave energy level reaching a given section of the coast is therefore an important factor which determines the degree of structural development of the mangrove forest. High energy levels are associated with erosion, destruction or deposition of berms which affect mangrove development. Low energy levels, however, are associated with a rapid process of island maturation, aging and death due to rapid salt accumulation.