The floodplains are a unique part of the Top End and they are quite new in geological terms.  Their soils are the result of millions of years of erosion and the deposits of the silt from the floods of the rivers as well as the impacts of the sea over the last six thousand years.  Many of the floodplains were mangrove forests a few thousand years ago, and changed to freshwater environments as the sea levels changed.  The rich soils combine with algaes and nutrients washed down from other habitats to create these very productive areas.  The paperbark swamps and areas fringing the floodplains are also very productive areas and provide for a wide variety of wildlife.