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Historical description of the morphology and hydraulic behavior of a bifurcation in the lowlands of the Grijalva River Basin, Mexico

Mendoza, Alejandro, Soto-Cortes, Gabriel, Priego-Hernandez, Gaston, Rivera-Trejo, Fabian
Catena 2019 v.176 pp. 343-351
historical records, lowlands, remote sensing, rivers, sediment yield, watersheds, Mexico
The bifurcation of a river is a transient condition caused by an avulsion where a channel is abandoned, and a new one is developed. The bifurcation may remain for an extended period. The Mezcalapa River, located in the Grijalva River Basin, in southwestern Mexico, has a record of several avulsions; the last one occurred in 1934 giving origin to the bifurcation Mezcalapa-Samaria-Carrizal that is still active. There have been significant changes in the flow distribution in the bifurcation during the last five decades, with flow distribution ratios oscillating from 0.1, that was attained by 1983 and again in 2017, to ratios of 2 observed by 2004. We utilized historical records of gauging stations, satellite imagery, and field data to characterize the hydraulic and morphologic behavior of the bifurcation. Historical data shows that a system of dams has reduced the sediment yield arriving at the bifurcation since 1966 and that the bifurcation planform is changing constantly. Interventions to control the flow distribution have a considerable impact on the behavior of the bifurcation.