Hydrology and Sediment Transport in a Highly Impacted Large Tropical River for Deforestation: The Araguaia, Central Brazil

Abstract:

With a drainage area of 377,000 km² and a mean annual discharge of ~ 6,420 m³/s the Araguaia River is the main tributary of the Tocantins River the principal system draining the central highlands of Brazil. The Araguaia River is a particularly sandy anabranching system that has been suffering geomorphologic and sedimentary changes because of the effect of extensive deforestation and land use, affecting the fluvial dynamics and leading to an accelerated erosion and sedimentation in the middle reach where the river flow through a wide alluvial plain.

This work presents the general geomorphic and hydrologic characteristics of the Araguaia and describes systematic results on bed load and wash load transport. We demonstrate that the river is undergoing a substantive increase in bed load transport and changes in its geomorphology. This is an outstanding current example of short term geomorphic response to deforestation in a large pristine tropical fluvial system without direct human interventions in the channel.