Large rivers, slow drainage rearrangements: The ongoing fluvial piracy of a major river by its tributary in the Branco River Basin - Northern Amazon

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Drainage capture between large rivers is a rare occurrence and as such the dynamics are poorly understood. In fact, most of our knowledge about this process is based on a previousstudy of the active drainage capture between the Orinoco and Negro rivers in the Northern Amazon Basin. The present study identifies and characterises a large drainage capture in progress of the Uraricoera River by its tributary the Uraricaá River within the Branco River Basin of the Northern Amazon. Our analysis of topographical features and a series of historical satellite images suggests that this type of river capture tends to be very slow and can take centuries to be complete. It was also established that river courses can be captured by their tributaries just upstream of where they converge. We suggest that accelerated headward erosion, driven by subsidence along the Branco and Negro rivers, is leading to stream piracy in the northern portion of the Amazon Basin.