Geomorphic diversity of the middle Araguaia River, Brazil: A segment-scale classification to support river management

Abstract

The complex mosaic of geomorphic units that characterizes the fluvial corridor of large rivers poses challenges to effectively describe and discriminate the landforms diversity, and is relationships with the hydrosedimentological dynamics and state of the system. Consequently, the classification of the diverse array of fluvial features into discrete segments can be a systematic and organized approach useful to sustain geomorphically-informed management strategies. Here we propose a methodological approach and characterize the geomorphic diversity of the middle Araguaia River by applying a classification of reaches into segments with a certain consistent level of morphological variability. A GIS framework developed for this purpose relied on the survey, analysis, and statistical treatment of morphological variables derived from remote sensing data. It allowed to differentiate 19 distinct reaches (R1-R19) that were further clustered into five major segments (SI-SV). We investigated the first-order controls of the fluvial style in each of the identified segments and found that changes in valley gradient influence in a major way the segments I, III, and IV, while the entrance of important tributaries and the nature of the valley floor are natural governing factors in segments II and V, respectively. The system exhibits a significant morphological diversity among segments, and it is strongly influenced by the late Holocene avulsion history of the river. Given the increasing pressure of human activities on the hydrological system, the present study can be of use to subsidize sustainable management plans aiming to safeguard the last large free-flowing river of the Cerrado biome, and our methodological proposal is valid for use in other large rivers worldwide.