Resumo

MARINO, Márcia Thelma Rios Donato; FREIRE, George Satander Sá  e  HORN FILHO, Norberto Olmiro. Grain size variations along the Fortaleza metropolitan region coastline, Ceará, Brazil. RGCI [online]. 2013, vol.13, n.3, pp.267-282. ISSN 1646-8872.  https://doi.org/10.5894/rgci411.

This paper presents a study of the long shore and cross-shore grain size distribution of sandy beaches along the Fortaleza Metropolitan Region (RMF) coastline. Statistical parameters were used to compare grain sizes along the coast and among the subgroup of beaches. The different percentage of the grain size distribution and statistical parameters were used for comparisons. The collection of 99 samples of surface sediments during spring tide allowed for the observation of seasonal changes in three distinct periods: rainy, dry and transition seasons. This coastline developed beaches with different hydrodynamic energy levels, exposed and semi-exposed, protected by elongated strips and discontinuous beachrocks, which reduce wave energy, protecting the beaches from coastal erosion. The extreme sectors are the most dynamic and of greatest susceptibility to the wave action and storm surge. The sedimentary dynamics is characterized by the high mobility of sediments along the beach that results from 1) the action of longshore currents, between the emerged and submerged parts, and 2) the weather variations. Because it is fully inserted in the RMF, the coastal plain between the Porto das Dunas and Praia do Futuro beaches has suffered and continues to suffer the negative consequences of rapid urbanization and population growth. That, in turn, brings significant imbalances in the relationship between society and nature and engenders, as its most striking effect, environmental degradation. The grain size characteristics of this coastline are strongly conditioned by the influence of hydrodynamic, wind, and weather agents, associated with the type, orientation, and location of the beach as well as the proximity and type of sediment source area. It is recommended that future work conduct stratigraphic investigations along the coastal plain, detailed analyses of sediments on the morphoscopy and mineralogy, morphodynamic and sedimentological monitoring of the coastline, bathymetry and facies analyses of the shoreface and inner continental shelf adjacent, and previous studies (often covering medium and long periods) for building coastal resorts.

Palavras-chave : Textural analysis; Seasonal variations; Morphodynamic beach.

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