Transporte longitudinal de sedimento na zona costeira de Natal/RN

The longshore sediment transport (LST) is determinant for the occurrence of morphological changes in coastal environments. Understanding their movement mechanisms and transport is an essential source of information for the project design and coastal management plans. This study aims to characterize, initially, the active hydrodynamic circulation in the study area, comprised of four beach sectors from the south coast of Natal, assessing the average annual LST obtained through three proven equations (CERC, Kamphuis and Bayram et al.), defining the best formulation for the study area in question, and analyze the seasonal variability and the decadal transport evolution. The coastal area selected for this work constitutes one of the main tourist corridors in the city, but has suffered serious damage resulting from associated effects of hydrodynamic forcings and their disorderly occupation. As a tool was used the Coastal Modelling System of Brazil (SMC-Brazil), which presents integrated a series of numerical models and a database, properly calibrated and validated for use in developing projects along the Brazilian coastline. The LST rates were obtained for 15 beach profiles distributed throughout the study area. Their extensions take into account the depth of closure calculated by Harllermeier equation, and regarding the physical properties of the sediment, typical values of sandy beaches were adopted, except for the average diameter, which was calculated through an optimization algorithm based on equilibrium profile formulation proposed by Dean. Overall, the results showed an intensification of hydrodynamic forcings under extreme sea wave conditions, especially along the headlands exist in the region. Among the analyzed equations, Bayram et al. was the most suitable for this type of application, with a predominant transport in the south-north direction and the highest rates within the order of 700.000 m3 /year to 2.000.000 m3 /year. The seasonal analysis also indicated a longitudinal transport predominance in the south to north, with the highest rates associated with the fall and winter seasons. In these periods are observed erosive beach states, which indicate a direct relationship between the sediment dynamics and the occurrence of more energetic sea states. Regarding the decadal evolution of transportation, it was found a decrease in transport rate from the 50’s to the 70’s, followed by an increase until the 2000’s, coinciding with the beginning of urbanization process in some stretches of the studied coastline.

Uso e ocupação do solo e a transformação da paisagem na faixa litorânea da Via Costeira, município de Natal/RN

The coastal area of the city of Natal due to its location and natural potentialities has been an area where we have experienced big changes in its environment, at the expense of several forms of use and human occupation. On the coast of Via Costeira beach the process of use and land occupation was structured at the end of 1970s and early 1980s, as a result of the government policy which has developmental essence, based on the settlement of plenty big enterprises by the Parque das Dunas/Via Costeira Project. This project was created to install in Natal, capital of the state, infrastructure equipment on this stretch of coastline consisted of dune fields and many parts of ecosystems which have high natural relevance and fragility that used to present a semi-isolation in the urban city, for the development of tourist activities, which is considered as a viable economic solution capable of setting right serious socioeconomic problems that had persisted there. According to what was said so far, this study aimed to analyze the forms of use and land occupation besides the change of the landscape along the Via Costeira coast in the city of Natal/RN. These changes often take place without considering the complexity and fragility of natural ecosystems involved. The geoenvironmental study was based on the geosystemic theory, thus It was possible to analyze the human interventions in the superficial aspects of landscapes holistically. The practical procedures were contemplated with literature searches, followed by field work where were fulfilled the recognition and general characterization of the area in order to investigate and analyze the main types of land occupation and its use that have taken place there since big buildings began to come out, being supported by the legislation whose laws are about protection and conservation of coastal natural resources. The research also includes the identification and evaluation of the main types of negative impacts caused due to different forms of use that induce environmental and social conflicts nearby this shore. Thus, It was carried out a spatial and multitemporal analysis from orthophotos, aerial photographs and others taken during the field work besides satellite images too. The information which is taken out from these instruments was used to draw maps related to land occupation, spatial impacts and other thematic maps. We worked on a hypothesis that the implementation of mega enterprises on Via Costeira and many different forms of intensified use by human actions, has not considered the natural aspects and restrictions of use in this area, these ones would be the main factors that brought on the suppression and degradation in this environment and consequently the transformation of the natural landscape.

Ventilação e prescrições urbanísticas: uma aplicação simulada para a Orla da Praia do Meio em Natal/RN

This work analyses a study on natural ventilation and its relation to the urban legislation versus the building types in an urban fraction of coastal area of Praia do Meio in the city of Natal/RN, approaching the type or types of land use most appropriate to this limited urban fraction. The objective of this study is to analyse the effects of the present legislation as well as the types of buildings in this area on the natural ventilation. This urban fraction was selected because it is one of the sites from where the wind flows into the city of Natal. This research is based on the hypothesis stating that the reduction on the porosity of the urban soil (decrease in the set back/boundary clearance), and an increase in the form (height of the buildings) rise the level of the ventilation gradient, consequently causing a reduction on the wind speed at the lowest part of the buildings. Three-dimensional computational models were used to produce the modes of occupation allowed in the urban fraction within the area under study. A Computational Fluid Dynamics (CFD) software was also used to analyse the modes of land occupation. Following simulation, a statistical assessment was carried out for validation of the hypothesis. It was concluded that the reduction in the soil porosity as a consequence of the rates that defined the minimum boundary clearance between the building and the boundary of the plot (and consequently the set back), as well as the increase in the building form (height of the buildings) caused a reduction in the wind speed, thus creating heat islands

Estudo de revestimentos inorgânicos com inibidor de corrosão aplicado na superfície do concreto

The corrosive phenomenon on reinforced concrete structures is one of the most founded pathologies on the coastal area. With the objective to prevent the process development, or even, retard its beginning, it was studied the application of inorganic covering over concrete surfaces, after its cure, as well as, evaluate the efficiency of the covering applied on the concrete in reducing its porosity of concrete preventing the entrance of aggressive agents to preserve the integrity of the existing armor inside it, comparing the result obtained with the body-of-proof reference, that didn´t receive covering protection. On the concrete production it was used Portland Cement CP II 32, coarse aggregate, fine aggregate and water from the local distributive. Two types of covering were used, one resin based of silicon and solvent and other white cement based, selected sands and acrylic resin. The concrete mixture adopted was 1:1,5:2,5 (cement, fine aggregate, coarse aggregate) and 0.50 water/cement ratio. With the concrete on fresh state was made the experiment test to determinate the workability. On the hardened state was made the concrete resistance experiment, absorption of water and electrochemical experiments, through polarization curves. Also was held optical microscopy and Scanning Electron Microscopy experiments to analyze the layer of the covering applied to the concrete surface and the interface between the concrete and the layer. The obtained results shows that the covering applied to the concrete surface didn´t affect the resistance towards compression. On the absorption of water occurred a diminution of the percentage absorbed, improving the concrete development by making it more impermeable towards the entrance of aggressive agents. The electrochemical experiment results confirmed the water absorption results; the body-of-proof covered presented larger protection towards the development of corrosives process and retarded the evolution of the corrosive phenomenon

Boto cinza (Sotalia guianensis, Van Benédén, 1864) (Cetacea, Delphinidae): Atividade aérea, forrageio e interações inter-específicas, na Praia de Pipa (Tibau do Sul RN) e estudo comparativo entre duas populações do Nordeste do Brasil

Sotalia guianensis is a small cetacean of the Delphinidae family, with coastal habits and whose area of distribution ranges from Florianópolis (27º35'S, 48º34'W), in Brazil, to Honduras (15º58'N, 85º42'W). At Pipa beach, on the south coast of RN state, in Brazil, the species occur throughout the year. The present study was carried out in two bays, which are bordered by cliffs. The animals were monitored from vantage points, using the "Ad libitum" and "all the occurrences" methods; during the years of 1999 and 2004. The study was divided in 4 chapters: Behavioral standards of two populations of gray dolphin, (Sotalia guianensis, Van Benédén, 1864) in the northeast of Brazil; Aerial activity of the gray dolphin: its possible function and the influence of environmental and behavioral factors; The influence of daily and monthly variation of the tides, of the period of the day and group size on the gray dolphin forage activity; kleptoparasitism interactions of frigatebird (Fregata magnificens, Mattheus, 1914) during the gray dolphin forage activity. The results have shown that the gray dolphin has a varied and complex behavioral repertoire. The leap is the most frequent behavior; the aerial activity is diffuse during daylight and is influenced by some factors, such as the level of the tide and social factors. The gray dolphin, when in the bay, most frequently feeds isolate or in small groups. The forage is diffuse during daylight; however, being more frequent in the morning and is influenced by the daily and monthly variation of the tide. At Pipa beach, kleptoparasitarian interactions were registered between the gray dolphin and the frigatebird (Fregata magnificens). The frigatebird forage strategy consists basically of two ways: to fly over great extensions searching for dead fish and to steal food (kleptoparasitism). These interactions were predominantly carried out between immature and female adult birds and adult and immature dolphins, and occurred during daylight. The present study can be considered an initial landmark to a better knowledge on the gray dolphin surface behavior, especially regarding the aerial behavioral repertoire and forage strategy of this species. However, it is necessary to continue these studies, so that we can understand better the complex social life of these animals and thus create effective measures for its conservation