What is the main rainy season river type that floods Amazonian várzea forests called?

The main rainy-season river type that floods Amazonian várzea forests is a whitewater river.

Whitewater rivers carry abundant suspended sediment, much of it eroded from the Andes. When these rivers overflow during the annual flood pulse, they deposit nutrient-rich material across várzea floodplains. This helps make várzea soils more fertile than those of many upland Amazon forests.

Várzea forests are seasonally flooded, unlike permanently flooded igapó forests associated mainly with acidic, nutrient-poor blackwater. The two forest types can look similar from a distance, but their water chemistry, soils, plant communities, and productivity differ.

Examples of major whitewater systems include the Solimões and Madeira rivers. River levels and flood timing vary across the basin, so seasonal inundation is not identical everywhere.