Planform geometry response of the upper-middle Araguaia River to changes in the hydro-sedimentary regime from 2001 to 2018

Abstract

The Araguaia River is characterized by a rapid geomorphic response to the degradation of the basin induced by land-use changes. The planform geometry in the upper middle-course of the Araguaia River was assessed over the 2001-2018 period. Thus, we extended to 53 years the pre-existing published time series data on the river’s morphology and its response to land use changes. Based on the analysis of multi-temporal remotely sensing images we quantified the morphometric parameters on islands and sandy bars and estimated erosive and depositional areas in the actual river system. From 1965 to 1998, the river partially changed its anabranching pattern, increasing the tendency toward braiding. The morphological changes from 2001 to 2018 reveal a new transitional phase of contraction of the channel’s active zone and a partial loss of braiding due to higher representativeness of the islands. This scenario responds to changes in the hydro-sedimentary regime over the last two decades. Given the expansion of the agricultural frontier and the proposals for the construction of four large dams along its main stem, the current state of adjustment of the channel-floodplain system must be considered in the management plans of this large river of the Cerrado biome.