What is the the largest fluvial group of islands in the world ?

lha Tupinambarana is the name of a former fluvial island bordered by rivers of the Amazon system in eastern Amazonas, Brazil. Today, it has been split into four completely separate parts by natural channels, just like those isolating it from the mainland—it is no longer one island, but four. The original island stretched from the municipalities of Parintins, in the northeast, to Nova Olinda do Norte, in the southwest. The combined area of the islands is to 11,850 km²