Typology of Argentine beaches: Composition, Tidal Range and Wave Energy

ISLA, FEDERICO; BUJALESKY, GUSTAVO; BERTOLA, GERMÁN; IANTANOS, NERINA; ESTRADA, ENRIQUE

Itajai

Simposio; VIII International Coastal Symposium; 2004

Universidade do Vale do Itajai

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 periods; within gulfs and rias outlets local waves are significantly lower and with shorter periods. Spring tidal ranges also vary, from Jess 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 texn1res, were aloo surveyed from the mesotidal regime of northern Patagonia. Finally, 35 macrotidal beaches were analyzed from southern Palagonia and Tierra del Fuego; some of them composed exclusively of fine sand, others composed of coarse gravel, with fine sand segregated along the beadi profile (low tide terrace). Microtidal beaches do fil. 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 single beach: reflective close to high tide and dissipative during low tide.