Channel morphology as a key factor to hydrological and sedimentological patterns in the largest fluvial ria lake of Amazonia

Abstract

Amazon ria lakes are geomorphological features still poorly known despite their great magnitude and uniqueness. The Tapajós ria comprises one of the largest natural channels in the world, measuring impressive 20 km in width in its lower reach. Important data on longitudinal distribution of matter and energy has been collected in the last decades, but far less attention has been given to its transversal variation. In this paper we analyze grain size and major element concentration of bottom sediment on Tapajós ria lake, sampled along transversal profiles, in order to investigate the importance of channel morphology on data interpretation and to better describe fluvial dynamics. Geomorphological analyses of the channel Digital Elevation Model (DEM) coupled with remote sensing products allowed us to describe depositional features along the ria. We observed that novel patterns might emerge when transversal distribution is considered. Our results also support that local drainages and processes such as marginal scarp retreat may have an important role on the ria infilling. This approach has the potential to be applied to other large fluvial systems in the world helping to increase our understanding of the processes that shape their morphology.