Typology of Argentine beaches

FEDERICO IGNACIO ISLA; BUJALESKY, GG; BERTOLA G R; IANTANOS, N.; ESTRADA ENRIQUE

journal of coastal research

CERF

Lugar: West Palm Beach; Año: 2006 p. 375 - 378

Morphodynamic-based beach models assume uniform grain-size availability. However, uniform grain sizes seldom occur in present beaches. Waves and longshore currents induce sediment distribution, parallel or transverse to the coastline.And tidal ranges condition the temporal effects of waves and wave-induced currents. Argentine beaches are particularly sensitive to these effects. Beach composition varies from fine sand to uniform gravel up to 5 cm in diameter.Atlantic waves are higher than 1 m and 10 sec period; within gulfs and rias outlets local waves are significantly lower and with shorter periods. Spring tidal ranges also vary, from less than 1 m in Buenos Aires coastline to more than 8 m in southern Patagonia. More than 78 beaches were seasonally analyzed from the microtidal coast of northern Buenos Aires Province. 20 beaches, composed of gravel, sand or both textures, were also surveyed from the mesotidal regime of northern Patagonia. Finally, 35 macrotidal beaches were analyzed from southern Patagonia and Tierra del Fuego; some of them composed exclusively of fine sand, others composed of coarse gravel, with fine sand segregated along the beach profile (low tide terrace). Microtidal beaches do fit to the morphodynamic model proposed by Australian researchers. Mesotidal beaches have a different behavior in regard to the sediment composition and wave effects. Macrotidal beaches behave in relation to the type of sediment and its availability: Dissipative beaches may occur where there is a significant source of sand. Gravel availability is responsible for a dual behavior of a single beach: reflective close to high tide and dissipative during low tide.