River channel avulsion in the Taquari River megafan of the Brazilian Pantanal: Remote sensing and modeling reveal recent and future changes

Abstract

The largest crevasse in the Taquari River megafan in the Pantanal, Brazil with a perennial flooded area of ∼500,000 ha, was initiated in 1997 and impacted the environment and people. Here, we spatially characterize and explored a model aiming at predicting the evolution of the rechanneling of the Taquari River within this huge flooded area. Our approach is based on a spatiotemporal dry/wet index (R), which measures the degree of moisture in six major land cover classes. The index was annually estimated from MapBiomas Landsat rasters between 1996 and 2021 and calculated for 142 grid cells (5 × 5 km each). Temporal regressions were then used to predict the state of individual grids in the long term, up to 2080. The results suggest a gradual and slow terrestrialization between 1997 and 2021 as areas returned to pre-avulsion levels, mainly in the eastern and northern limits, closer to the crevasse. Modeling projections suggest that river rechanneling of the Taquari River might be completed by 2080 with its new mouth on the Paraguay-Mirim River. Large areas that are currently aquatic (open water, flooded soils, and flooded vegetation) are predicted to return to terrestrial state (forests and pastures) in the long term.