Backswamp (distal floodplain, floodplain wetland, floodpond, floodplain lake)

Position: Floodplain

 

Form

The distal floodplain, at valley margins, is typically the lowest area of the valley floor. They are major storage units of fine-grained, vertically accreted, suspended load sediments. Morphology is typically fairly flat (or has low relief), with depressions. Ponds, wetlands and swamps commonly form where lower order tributaries drain directly onto the floodplain.

 

Process description

Forms when the reduction in energy gradient from the proximal to distal floodplain only allows suspended load materials to be transferred to the backswamp. This results in slow rates of fine-grained vertical accretion in these settings. A distinct gradation in energy with distance from the channel may result in pronounced textural segregation across the floodplain. Backswamps, wetlands, lakes and pond features are common in these poorly drained (unchannelled), low-energy, vertically-accreting environments. Naturally colonised by dense aquatic/swamp vegetation that traps fine-grained suspended-load sediments. This promotes accumulation of cohesive, organic-rich mud. Materials are typically highly bioturbated.