Anthropogenic disturbances drive the morphological and sedimentary changes of the Cuiabá River, Pantanal, Brazil: a remotely sensed approach

Land use changes and dam construction have impacted sediment yield in river catchments worldwide. This is especially true in central-west Brazil, where most of the main watersheds have been deforested and rivers, such as the Cuiabá, have been dammed in the last 50 years. Here, we investigated the geomorphological and sedimentary responses of the Cuiabá River to land use changes and dams since 1985, using a time-series of Landsat images to quantify fluvial bars, channel width, channel migration rate and suspended sediment concentration (SSC). Our results showed an increase in the area occupied by fluvial bars and in SSC between 1985 and 2000, driven by natural vegetation conversion to agriculture. However, construction of the Manso Dam in 2000 led to a decrease in bar area, migration rates and SCC downstream. The SSC time-series also showed that sediment production remains high up to the present day in the monitoring section upstream of the Manso Dam, triggered by new waves of deforestation since the early 2000s. We conclude that land cover change led to increased sediment supply to the Cuiabá River, especially before the 2000s. However, this effect was surpassed by dam constructions in the watershed, which drove a significant decrease in sediments exported downstream.