Mapping spatial-temporal sediment dynamics of river-floodplains in the Amazon

Abstract

Abstract Water composition in floodplains plays a key role in ecological processes and is affected by both local water sources and flooding from the main river. Despite local studies, still lacks a complete understanding on the relationship between hydrological processes and sediment distribution in the river-floodplain system of the Amazon basin. This paper presents the first mapping of the dynamics of suspended sediments in rivers and lakes (>0.25\u202fkm2) of central Amazon, considering different water types. Previous studies have considered only white-water rivers with high sediment concentration. This study also describes some river-lake systems in terms of their spatial-temporal pattern of sediments and water flows. Time series between 2003 and 2017 of red and infrared reflectance of Moderate Resolution Imaging Spectroradiometer (MODIS) images were temporally filtered to retrieve incomplete and low-quality data. These images were assessed as a proxy of the surface suspended sediments concentration; and maps of the spatial-temporal variation of sediments were created, such as the class frequency map. This map represents a 15-year frequency at which each pixel remains in one of the surface suspended sediments concentration classes: high, moderate, and low, with an overall accuracy of 71%. Our findings allowed to observe the variation of sediment concentration along the Solimoes-Amazonas River, such as, for instance, its increase from the confluence with the Tapajos River to the mouth. Some hydrological processes were also observed in lakes of the middle reach, such as overbank flow and resuspension of sediments in depression lakes. In some ria lakes, the main water source comes from local basin with the backwater promoting sediment input in these lakes during the low-water period. The maps produced by this study are available and useful for supporting biogeochemical studies.