COMMENT ON “TEMPORAL GEOMORPHIC MODIFICATIONS AND CLIMATE CHANGE IMPACTS ON THE LOWER COURSE OF THE SÃO FRANCISCO RIVER, BRAZIL” BY TORRES ET AL. (2023)

Resumo

Torres et al. (2023) argued that the Lower São Francisco River (LSFR) has undergone a significant morpho-sedimentary process in recent decades. The work applied remote sensing techniques in a multi-temporal analysis (1986–2020) to quantify sedimentation and erosion processes. Moreover, the Modified Normalized Difference Water Index (MNDWI) was used to indicate the narrowing of the channel. The authors examine how precipitation, runoff, MNDWI, and sedimentation are interrelated. They found that lower precipitation, reduced runoff, and increased sedimentation are correlated. However, the investigation strategy and analysis of the results present several limitations in the study of large tropical rivers. We argue here why the observation of increased sedimentation in the investigated area may not be considered valid for other areas of the LSFR. We also explain why the applied statistical relationship (precipitation, flow, and sedimentation) is inadequate.  Our concern is that the use of results from an area that exhibits a transitional channel-pattern zone may be used as knowledge base for future interventions to repair a fluvial system as sensitive and complex as the São Francisco River.