Avulsion at a drift-dominated mesotidal estuary: The Chubut River outlet, Patagonia, Argentina

ISLA FEDERICO I; ESPINOSA, MARCELA; RUBIO BELEN; ESCANDELL ALEJANDRA ; GERPE MARCELA; MIGLIORANZA KARINA SILVIA BEATRIZ; REY DANIEL; VILAS FEDERICO

JOURNAL OF HYDROLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015

0022-1694

The Chubut River flows from the Andes to the Atlantic Ocean, and is interrupted by a single dam built atthe middle valley. The lower valley is dominated by the aggradation of an alluvial plain induced by a com-plex of spits that enclosed the inlet in the last 5000 years. The river has reduced its flow because theblocking of the upper basin by terminal moraines during the Upper Pleistocene. At least the last two mar-ine transgressions have flooded this estuary, and contributed to the aggradation during regressions. Thearea is of particular interest in regard to irrigation channels practiced since the XIX century. Today, themean monthly flow is less than 10 m3/s although peaks of 95 m3/s have been recorded in Gaiman in July2001. The dynamics of the estuary is dominated by waves (wave-dominated estuary) as tidal effectsattenuate in less than 5 km. Three vibracores were collected within this floodplain: (a) at Gaiman, an areawithout any effect of the sea (35 km from the coast); (b) at Trelew, at the former avulsion plain of theriver (18 km from the coast); and (c) at Playa Magagna, a saltmarsh located 0.4 km from the beach.