Recent geomorphological evolution of channel bar in Magdalena River (Colombia) due to natural and anthropogenic interferences

The growing establishment of port structures in estuarine regions has resulted in alternated sedimentation patterns and new geoforms. The primary purpose of this study is to understand the recent formation and geomorphological evolution of the fluvial bar in the final portion of the Magdalena River. The geomorphological evolution analysis was made possible using Geographic Information Systems tools, satellite images, and bathymetric data. The studied bar formed and stabilized through anthropic and natural factors such as port structures (obstacles to sediment transport), channel morphology, and natural- and anthropic-caused variation to the sediment supply. The lateral bar formation, adjacent to port structures, began in 2017 with surface runoff accumulating and anchored on the riverbank since 2018. At present, the bar covers 45% of the original river width, and an approximate sediment volume worth 4,000,000 m3 has accumulated. Changes in the navigable channel result in slope modification from 2.02 degrees to 5.36 degrees. The construction of port structures, i.e. new pile bridges, changes the natural sediment flow, because they are obstacles, trapping sediments downstream. This period coincides with the end of a weak El Nin similar to o cycle, subsequent to a La Nina period also of low intensity, with reduced precipitation rates resulting in a decrease in flow, and therefore contributing to an increase in sedimentation. The observations suggest that it is crucial to understand the channel bars' morphology and origin to avoid possible economic and social impacts due to the disruptions in navigation.

Automated summary

This study focuses on the recent formation and geomorphological evolution of the fluvial bar in the final portion of the Magdalena River. The analysis reveals that anthropic and natural factors such as port structures, channel morphology, and sediment supply variation play significant roles in the formation and stabilization of the bar. The observations also highlight the importance of understanding the morphology and origin of channel bars to avoid potential economic and social impacts caused by navigation disruptions.