Author(s): Gaston Priego; Alejandro Mendoza; Fabian Rivera; Eliseo Carrizosa; Ramon Dominguez

Linked Author(s): Alejandro Mendoza, Fabián Rivera

Keywords: River bifurcation; Sediment yield; Flow distribution; Avulsion; Vulcano

Abstract: It is well known the effects that a dam produces downstream of a river system. It disrupts the equilibrium due to the interruption of the sediment transport, that causes erosion and avulsion. A particular case occurs in a river in the southeast of Mexico. The Mezcalapa River has a dam system, and downstream there is a bifurcation that developed an unsteady flow distribution, apparently after the commissioning of a system of dams. The changes have been so significant, and one of the diffluentes of the bifurcation captured most of the flow gradually that during 1999 caused a severe flood in Villahermosa City with more than 600,000 inhabitants. Besides the effect of the dams, one hypothesis of the changes of morphology of the bifurcation and the change in the flow distribution that we explore here is related to the sediment yield in the basin. Today, to control the flow in the bifurcation, a structure was build in one of the diffluents. However, the high sediment yield in the zone is causing a partial close of this branch. If this process continues with the same pattern, a total closure of such diffluent is possible. To understand the role of the sediment yield, we did a multi-spacial survey during the last five decades. We used Land sat images from 1976 and the infrared spectrum to analyze the river. We identified a significant source of sediments: A Vulcano. The Chichonal Vulcano located around 60 km upstream of the bifurcation, erupted in 1982 and threw a large amount of ash into the river system. Today, almost four decades later, the effect remains and is needed to implement a strategy to manage these sediments along the river.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022815

Year: 2022