skip to primary navigation skip to content
 

Background

Floodplains and floodplain woodlands are vital elements in the natural landscape. They act as buffers between adjacent land (farmland, forest plantations etc.) and river channels, they store excess water temporarily during flood periods, and they provide wildlife habitats and corridors for species dispersal. They have multiple hydrological and ecological functions, but these have been highly disturbed by environmental change, cultivation, urbanisation, industrial development and water resource management.

A floodplain comprises not only the river and active channel, but also all adjacent sections of the surrounding landscape presently influenced by fluvial processes and the presence of a water table. Typically, the natural floodplain may have oxbow lakes in old river channels, backswamp deposits of fine sediments, ridges and swales on the convex bends in the river and areas of sedimentation (aggradation) and erosion (degradation), formed as the river migrates laterally across the floodplain. A diverse vegetation community in various stages of succession occurs along the resulting moisture and disturbance gradients, exploiting the complex range of habitat types and moist, fertile soils. The response of this mosaic of vegetation communities to disturbances is spatially and temporally complex and is therefore, difficult to predict.

Many floodplains have suffered a loss of natural function, and their ecological health and biodiversity have been severely degraded .This has led to an interest in the potential for restoration and rehabilitation of floodplains. Efforts to date have focused mainly on small rivers, but there is now a need to shift the emphasis to floodplains and river corridors in larger river systems.

The Floodplain Biodiversity and Restoration project is based on the assumption that floodplain hydrology is frequently the most important factor influencing biodiversity. The frequency, magnitude and duration of flooding events, erosion and deposition patterns, and patterns of water table recharge have been shown to fundamentally affect the regeneration success of riparian species, and therefore any restoration initiative. While the flow needs of within-channel species are increasingly well-understood as the Instream Flow Incremental Methodology and PHABSIM are more widely used, understanding of the flow needs of riparian species has lagged behind.

Aerial view of the Drôme River near Crest, France showing various destructive elements in the floodplain landscape including a site of gravel extraction in the foreground, river channelization in the background and the encroachment of agricultural land. (N. Barsoum, 1996)