PERILLO Gerardo Miguel E.
congresos y reuniones científicas
Ebb deltas of the Negro River Estuary, Argentinean Patagonia
Conferencia; 2022 Particles in the Americas Conference (PiA 2022); 2022
Institución organizadora:
Particles in the Americas (PiA)
Argentina has a coastline of approximately 6,816 km, although the number of estuaries is relatively small compared to countries of similar size. In terms of tidal regimes, they cover the whole range from microtidal to hypertidal. Even though the Negro river estuary is in the boundary between mesotidal and macrotidal regimes, its mouth present a well-defined ebb delta due to the accumulation of sediments on both sides of the mouth, forming two banks (La Hoya and Miguel) without a frontal shield. This structure has a main channel dominated by ebb currents and marginal channels dominated by flow currents. A study employing old charts documented the growth trend of the Miguel Bank in the direction of the littoral drift, and the La Hoya Bank tends to migrate towards the coast of Buenos Aires. While a marginal channel of the Miguel Bank has a strong influence on the littoral dynamics coming from the Balneario El Condor. Tidal range is mixed semi-diurnal. In addition, the Negro River is the end member to a fluvial system integrated by the Patagonian rivers Limay, Neuquén, and the Negro itself. All three rivers are tributaries on the estuary. However, since the 1970’s the Limay and Neuquén rivers have reduced their sediment contribution due to the construction of several dams and hydroelectric power stations. The major fluvial sediment inputs to the estuary banks come from the Negro River, from its three valleys Upper, Middle, and Lower. The development of an extensive meander system in the Middle Valley restricts some of the sediment from the Upper Valley and gives the possibility of greater carrying power to the waters of the Lower Valley. We conclude that the tidal delta historic evolution is closely related to the sequential sediment retention at the various dams. However, since the 70´s its evolution is mostly due to the tidal and littoral dynamics.