Lauro Júlio Calliari

Extreme storm surges in the south of Brazil: atmospheric conditions and shore erosion

The region under study is regularly subject to the occurrence of storms associated with frontal systems and extratropical cyclones, since it is located near one of the cyclogenetic regions in South America. These storms can generate storm surges that cause anomalous high sea level rises on Cassino Beach. The use of reanalysis data along with an efficient technique for the location of the cyclone, using a vorticity threshold, has provided a new classification based upon the trajectories of events that produce positive sea level variation. Three patterns have been identified: 1) Cyclogenesis to the south of Argentina with displacement to the east and a trajectory between 47.5oS and 57.5oS; 2) Cyclogenesis to the south of Uruguay with displacement to the east and a trajectory between 35oS and 42.5oS; and 3) Cyclogenesis to the south of Uruguay with displacement to the southeast and a trajectory between 35oS and 57.5oS. Maximum water level elevation above the mean sea level and beach erosion were associated, respectively, with winter and summer storms. Cassino beach displayed a seasonal morphological behavior, with short periods of episodic erosion associated with winter storm events followed by long periods of accretion characterized by the dominance of fair weather conditions.

Morfodinâmica praial: uma breve revisão

Desde o inicio dos anos 30 perfis de praia foram classificados em um dos dois tipos: perfis de tempestade ou perfis de ondulacao associados, respectivamente, com ondas de alta e baixa esbeltez. Mudancas no perfil praial envolvem muitas variaveis, tornando muito dificil a formulacao de modelos de predicâo de comportamento praial. Somente a partir da decada de 70, as caracteristicas dos sedimentos c os processos de transformacao de ondas operantes na plataforma interna e antepraia, acoplados com a morfologia tridimensional e a hidrodinâmica da praia, comecaram a ser estudados de maneira integrada. Tais estudos levaram a um melhor entendimento do comportamento de sistemas praiais e zonas de arrebentacao e tambem a formulacao de modelos sequenciais de comportamento morfodinâmico daqueles sistemas. Apresenta-se aqui uma breve sintese dos principais trabalhos e modelos introduzidos pela escola australiana de geomorfologia costeira na area de morfodinâmica praial e o resultado de sua aplicacao em algumas praias do sul e sudeste do Brasil.

Erosion or Coastal Variability: An Evaluation of the DSAS and the Change Polygon Methods for the Determination of Erosive Processes on Sandy Beaches

ABSTRACT Albuquerque, M., Espinoza, J., Teixeira, P., de Oliveira, A., Corrêa, I., Calliari, L., 2013. Erosion or Coastal Variability: an evaluation of the DSAS and the Change Polygon methods for the determination of erosive processes on sandy beaches. There has recently been growing concern about issues related to erosive processes on sandy beaches and climate change in the scientific community. Several methodologies have been proposed in the worldwide literature to quantify coastline retreat on shorelines in an accurate way. It has been questioned whether these methodologies show the erosive process or the shoreline variability in a certain area. From this perspective, this paper aims at characterizing the accuracy of the Digital Shoreline Analysis System (DSAS) and the Change Polygon Method in the studies of regression on shorelines which are prone to erosion. Data collected by a GPS-RTK along Hermenegildo Beach, located in the south of Brazil, and the geo-referencing of satellite images enabled the outline of the shoreline in different periods with the use of both methodologies and the analysis of their accuracy. The DSAS showed good correlation among data; however, since it uses equidistant transects, it could not account for some features in the shape of crests or troughs in the area under study. The DSAS is based on the calculation of rates of statistical variations in a series of vector data that represents the shoreline. In order to correct those features that were not accounted for by the transects, more lines would have to be created so that a larger stretch of the area under study could be reached. The Change Polygon Method, based on the creation of polygons with lines from different periods, may be used to calculate the area of the region under study and compare it with areas from other periods. The calculated shoreline length led to the definition of the shoreline displacement in meters per year. The correlation was 13% (R2=0.131) in terms of reliability for the DSAS whereas it was 94% (R2=0.9418) for the Change Polygon Method, considering the same shorelines. Results showed that the Change Polygon Method is more reliable to evaluate variations in areas and shorelines by comparison with the DSAS. Choosing an efficient method to identify problematic areas with economic and social risks is fundamental to define strategies for proper management of places with erosive processes.

Beach morphodynamics: a brief review

• Abstract: Since the early 1930s, beach profiles have been broadly classified in one of the two types: storm profiles or swell profiles associated, respectively, with steep or low waves. Changes in beach profiles involves so many variables that becomes very difficult to obtain a model which can account for a sucessfull explanation or prediction of these changes. Only in the early 1970s. the sediment characteristics, the process of wave transformation in shallow waters and the coupling between the three-dimensional morphology and the hydrodynamics were sistematically analyzed in order to get a better understanding of the processes responsible for beach changes and its evolutionary sequences. In this paper a brief review about the sucessfull beach morphodynamic models developed by the Australian school of coastal geomorphology is presented as well as some results of this approach applied to some of the southern and southeastern Brazilian beaches.

Marine intrusion and freshwater discharge as opposite forces driving fish guilds distribution along coastal plain streams

Abstract This work investigated variations in fish guilds along marine surf zone to freshwater reaches of coastal plain streams and their relationships with environmental factors. Fish and abiotic data were collected monthly during 1 year and an automatic image-recording system was used to monitor marine intrusion events. Aside ephemeral salinity gradients produced by storm surges, freshwater conditions prevailed inside streams. Despite of that, fish habitat use guilds were spatially distributed according to their salinity tolerance, with marine species occurring mainly in the stream site near the adjacent surf zone and non-salinity tolerant freshwater fish in the upstream site. Marine intrusion was the main factor correlated with the entrance of marine-related fish into streams during summer. In contrast, higher rainfall during colder months prevented the dominance of marine species. This work highlighted that spatial segregation in fish habitat use guild could occur even in the absence of long-lasting salinity gradients, since active colonization by euryhaline fish and sporadic marine intrusions can lead to the occurrence of marine-related fish in coastal plain streams. Future studies should evaluate if this marine intrusion role on fish of coastal plain streams would be affected by changes in sea level and rainfall in a global warming scenario.

Intertidal Bathymetry Estimation Using Video Images on a Dissipative Beach

ABSTRACT Sobral, F.N.C., Pereira, P.S., Cavalcanti, P.G., Guedes, R.M.C., Calliari, L.J., 2013. Intertidal Bathymetry Estimation Using Video Images on a Dissipative Beach. Located at southern of Brazil, Cassino beach is a multiple sandbar beach. A video technique to map intertidal bathymetry changes was applied using CMYK color model to find the waterline position, hydrodynamic data and runup 2% (R2) parameterizations. Linear regression between waterline video detected and elevation estimated with in situ measured maximum swash, showed a correlation coefficient of r2=0.82 and r2=0.91, respectively. Rmse values for those comparison was 10.14 m (horizontal detection) and 0.12 m (elevation). The empirical swash coefficient (Kosc) was 1.08 with a total error δz of rms=0.25 m and represents a waterline underestimated to compensate the overestimated horizontal determination. The principal error was found to be at horizontal position, which means that the R2 parameterization was efficient. The estimated bathymetry temporal evolution changes showed a similar morphologic evolution when compared with beach profile with a total rmse of 0.13 m.

High-energy events and short-term changes in superficial beach sediments

Laboratorio de Oceanografia Geologica, Fundacao Universidade Federal do Rio Grande (Av. Italia, km 8, Campus Carreiros, 96201-900 Rio Grande, RS, Brasil) lcalliari@log.furg.br The sediment distribution along modern beaches is the result of the complex interaction between the sediment source, the wave energy level and the general offshore slope upon which the beach is constructed (KOMAR, 1998). Sediments tend to be sorted according to the energy levels that the beach is exposed, so that beaches exposed to higher wave energy levels are expected to be composed by coarser sediments. In the composition of beach sediments, quantities of heavy minerals might be present. Since they are denser than quartz grains, they present a different hydraulic behaviour when compared to lighter grains. The behaviour of heavy minerals has been studied mainly related to erosional and/or accretional beach processes (e.g. SLINGERLAND, 1977; KOMAR et al., 1989; KOMAR, 1998). The straight wave-dominated southernmost coastline of Brazil is characterised by an extensive sandy coastal plain. The study area comprehends 220 km of sandy beaches located between the Patos Lagoon inlet and the Uruguayan border (Fig. 1). Beaches in this region are classified as dissipative and intermediate, associated to one or two longshore sandbars (CALLIARI; KLEIN, 1993). Seasonal variations are present, with accretion profiles during spring and summer and erosion profiles during autumn and winter. The climate of this coastal region is under the control of the high-pressure centre of the Atlantic anticyclone, whose latitudinal migration and the passage of polar front systems in 6-10 days intervals have a seasonally modifying influence on the climate. During cold fronts events, more common during winter months, SW winds become stronger (8 m.s

Ocean Beaches of Rio Grande do Sul

Beaches along the Rio Grande do Sul (RS) coast are fully exposed with the exception of the extreme northern end where a rocky headland composed of sandstone, basalt and volcano-clastic sequences provide a small degree of protection to coastal dynamics. The beaches generally consist of fine quartz sand with a low gradient swash zone usually containing low-relief beach cusps. Beaches range between intermediate and dissipative, with beach state controlled in part by grain-size variations through the contribution of shell fragments, gravel and coarse quartz sand. This wave-dominated coast is episodically exposed to storm waves, which favors the formation and maintenance of two to three shore parallel sand bars. Most of the beaches possess distinct hazard to bathers associated to their beach state and hazard rating. The longshore bar and trough (LBT) and rhythmic bar and beach (RBB) states are very common and the troughs are usually deeper than the height of the bathers. The combination of higher beach population during summer seasons and rip-dominated intermediate beaches result in the most hazardous beaches along the northern littoral and in the extreme south. Other beach hazards are related to the presence of washouts and flooding, as well as, to episodic deposition of fluid mud at the surfzone and beach as a result of anthropogenic influence. Approximately 80 % of the coastline is undeveloped and the main impacts are associated to car traffic and litter represented by solid waste and plastic beads. Foredunes along the littoral are affected by changes in coastal orientation in relation to the prevailing northeast winds and beach morphodynamics and range from well-developed to non-existent.

Coastal Hydrodynamics and Longshore Transport of Sand on Cassino Beach and on Mar Grosso Beach, Southern Brazil

ABSTRACT Fontoura, J.A.S.; Almeida, L.E.; Calliari, L.J.; Cavalcanti, A.M.; Möller, O., Jr.; Romeu, M.A.R., and Christófaro, B.R., 2013. Coastal hydrodynamics and longshore transport of sand on Cassino Beach and on Mar Grosso Beach, southern Brazil. The hydrodynamic and morphodynamic parameters of a region in southern Brazil were determined by collecting sediments with stream traps (bedload and suspended load) in the surfzone and capturing images, studying topography, and researching sedimentology with the help of a movie camera, a total station, and laboratory work. Data on deep-water waves were garnered with a CPTEC/INPE model. Field work was carried out in 50 field trips during a 1-year period; 42 out of 50 trips focused exclusively on hydrodynamic and morphodynamic data, whereas eight of the trips were also used for collecting sediments. In addition, data on wind direction and velocity and on the longshore currents were also collected. All data were obtained in normal atmospheric conditions. Field work was carried out in six cross-shore profiles along Cassino Beach and Mar Grosso Beach (three profiles on each side of the estuary of Patos Lagoon).

Depósitos fosfáticos marinhos na costa sudeste e sul do Brasil: potenciais áreas de ocorrência identificadas com dados de retroespalhamento acústico do fundo e sedimentológicos analisados sobre mapa batimétrico 3D

Bathymetric, sedimentological and seabed acoustic backscatter data were integrated into a 3D GIS (Geographic Information System). 38 kHz echo sounders were used to collect data over 14,596 nautical miles during six fish biomass assessment cruises over the continental shelf, slope and adjacent oceanic regions between Chui-RS (34°S) and Cape Sao Tome-RJ (22°S), Brazil. The bathymetric set of data were complemented with satellite altimetry and also with data from general bathymetric charts in order to build a bathymetric grid with 5,397,090 points. From this grid, a 3D virtual representation of the seabed was generated, using the language for description of three-dimensional interactive environments X3D. Bottom features such as Rio Grande Cone and Terrace, Sao Paulo Plateau and others, were identified in the bathymetric maps. 3D GIS implementation allowed to analyze backscatter and sedimentological information over the bathymetric grid, demonstrating to be a useful tool to highlight areas with characteristically phosphatic deposits. 3D GIS proved to be more valuable than two-dimensional representations because allowed observation of details and interpretation of information from different not static viewpoints.