Dieter Muehe

Estado morfodinâmico praial no instante da observação: uma alternativa de identificação

Determinations of the morphodynamic state of beach and surf zone were made on four beaches in Rio de Janeiro state, with two beaches located northward and two westward of Cabo Frio. Twenty four monthly measurements of beach and surf zone profiles associated to measurements of wave height and period, sediment settling velocity as well as swash climate were made during low spring tide. The beaches were classified by their modal morphodynamic state, a differentiation due to different wave climate and sediment characteristics. With exception for the reflective state, low correlation between the predicted and observed Morphodynamic State were obtained using Deans parameter (Ω). This is a consequence of the low correlation between the grain size (and settling velocity) of the beach face sediments and the topographic gradient, when applied to a single beach. A new approach for the identification of the Morphodynamic State is proposed by inferring the beach and nearshore morphology through the comparison of the wave height and period in the outer breaker zone to the height and semi-period of wave in the swash zone.

The smartline approach to coastal vulnerability and social risk assessment applied to a segment of the east coast of Rio de Janeiro State, Brazil

A growing awareness of increasing trends in coastal erosion and flooding due to climate change is triggering a demand for the rapid assessment of the potential responses of the coastlines around the world, principally in locations where human occupation is especially endangered. Investigations of present and future physical vulnerability and associated social risk have, therefore, become crucial for coastal management. In order to provide a quick and simple methodology for the identification of vulnerable coastal segments, Sharples (2006) has proposed a mapping methodology, called the smartline approach, which consists of representing, by means of simple lines, a geomorphic classification of the hinterland, backshore and beaches. The aim of this paper is to apply the smartline approach to coastal vulnerability assessment with inclusion of social data. The results show that this methodology is appropriate for the indication of coastal segments with varying degrees of vulnerability to erosion and flooding and for the appraisal of the resulting social risk.

Geomorfologia, cobertura sedimentar e transporte de sedimentos na plataforma continental interna entre a Ponta de Saquarema e o Cabo Frio (RJ)

A plataforma continental interna defronte a restinga da Massambaba - um sistema de duplos cordoes litorâneos localizados entre Saquarema e Arraial do Cabo, com 48 km de extensao - apresenta topografia regular, interrompida por raros afloramentos de rochas do embasamento cristalino e por ocorrencias localizadas de arenitos de praia. Um amplo afloramento destes ultimos ocorre na faixa batimetrica de 48 a 60 m, correspondendo a posicao da linha de costa cerca de 10.000 anos atras. Outro afloramento de arenitos de praia, de reduzida dimensao, ocorre proximo ao perfil S-4, a distância de 50 m da face da praia, em profundidade de 4 m. A cobertura sedimentar, sem aporte significativo de sedimentos terrigenos, e constituida predominantemente por areias quartzosas reliquiares. O gradiente batimetrico apresenta declividade elevada, atipica para uma plataforma passiva, atingindo o limite distai da plataforma continental interna, a isobatimetrica de 60 m, a uma distância da ordem de 4 milhas nauticas da linha de praia. O padrao de distribuicao granulometrico apresenta gradientes de decrescimo em direcao a leste, isto e, em direcao ao Cabo Frio, e em direcao a maiores profundidades. A diminuicao do tamanho granulometrico em direcao ao Cabo Frio e atribuida como sendo resultado do aporte de sedimentos terrigenos atraves de um sistema de drenagem pleistocenico, interrompido pela construcao do cordao litorâneo mais interiorizado, e a remobilizacao dos sedimentos por acao de ondas e correntes com transporte residual em direcao a leste.

Beach morphodynamic state at the moment of observation: an alternative for identification

. Abstract: Determinations of the morphodynamic state of beach and suef zone were made on four beaches in Rio de Janeiro state, with two beaches located northward and two westward of Cabo Frio. Twenty four monthly measurements ofbeach and suefzone profiles associated to measurements of wave height and period, sediment settling velocity as well as swash c1imatewere made during low spring tide. The beaches were classified by their modal morphodynamic state, a differentiation due to different wave c1imate and sediment characteristics. With exception for the reflective state, low correlation between the predicted and observed Morphodynamic State were obtained using Deans parameter (Q). This is a consequence of the low correlation between the grain size (and settling velocity) of the beach face sediments and the topographic gradient, when applied to a single beach. A new approach for the identification of the Morphodynamic State is proposed by inferring the beach and nearshore morphology through the comparison of the wave height and period in the outer breaker zone to the height and semi-period ofwave in the swash zone.

Can the trapping of shoreface sand by mud layers induce coastal erosion? The example of the Paraiba do Sul river outlet, Northern Rio de Janeiro state

Husky Duck Ltda. (Estrada Velha da Pavuna, 4522, 20761-171 Rio de Janeiro, RJ, Brasil) e-mail: huskyduck@terra.com.br A coastal segment of about 4 km length, located immediately southward from the Paraiba do Sul river mouth, forming the ocean beach of the town of Atafona, in the north of Rio de Janeiro state (Fig. 1), has experienced severe coastal erosion (ARGENTO, 1989). In consequence, tens of houses have been destroyed by the erosion as well as by foredune migration.

TRADIÇÃO DA GEOGRAFIA NOS ESTUDOS COSTEIROS

Geography has a strong tradition on coastal studies since, at least, the XVIII century. The studies of Marine Physical Geography and coastal geomorphology as also, recently, the interest on social aspects of the coastal zone, demonstrate the course of this tradition. This paper presents a retrospective of this tradition since the rise of the scientific interest about the littoral, passing to the physical and social approaches of the ocean and coastal studies and, finally, concluding with an analysis about the geographer’s insertion in recent publications. The brief historical and statistical data discussed evidence the geographical tradition on coastal studies and, at the international context, the significant position of this science, reflected in two important scientific magazines.