The river corridor is a diverse zone in terms of its scale, situation and character, and is one which is heavily modified by human activity. In many countries, river management has been driven by flood defence requirements, land drainage and also the desire of riparian landowners to have stable, well-defined river banks. As a result, channel cleaning, embanking, reinforcement and straightening have been widespread because they maximize the flood conveyance of the channel and maintain an essentially stable river course. As a consequence of these activities the special attributes of river corridors have in the past been largely ignored by river managers. Fortunately, recent attempts to improve "ecosystem health" in freshwater environments has meant that river conservation and rehabilitation measures have sought to re-introduce some of the attributes of river corridors and wetlands in terms of, for example, their sediment and solute attenuating capacity and their role as temporary flood storage areas.

River corridors span a wide scale. At one end of the spectrum, the corridor may comprise a narrow strip of riparian vegetation separating the hillslope from the river channel. At the other end, the corridor may consist of a wide and complex flood plain including many landscape units. The natural function of the corridor is to mediate the transport of water and dissolved and particulate material to the river network. The sedimentological and biogeochemical functions that the river corridor provide are particularly important to the long-term restoration and conservation of the river habitat. In research terms, there is a need to understand better the biogeochemical processes and transportation involved, including the manner in which the river corridor acts as a filter for particulate materials and as a sink for nutrients and other materials in soluble form, and how these fractions are affected by complex interactions between surface, hyporheic and groundwater flow in this environment. Better understanding of river corridor and wetland processes will help ensure that measures such as the introduction of riparian buffer strips (bands of well-developed riparian vegetation along the channel margin, including wetlands) by river managers, in the belief that they can help to process diffuse contaminant runoff from agricultural land, are more likely to succeed. Such buffer strips intercept eroded sediment and sediment-associated contaminants in overland flow and may remove soluble and colloidal nutrient forms from water draining laterally into the river channel. However, these processes are complex and thus the success of such buffer strips in attenuating and/or modifying nutrient transfer is still uncertain.

This edited volume addresses research issues focused on the biogeochemistry of the riverbank with special reference to data observation, modelling and attempts to restore these environments. The contents have been subdivided into a number of sections with specific themes. Thus there are a number of papers that focus on hydrochemistry, in particular, the role of organic carbon in upland wetlands and in flood plain rivers. A second section focuses on nutrients in the river corridor and wetland environment, where the emphasis is on understanding nitrogen and phosphorus dynamics. A large number of papers examine the river corridor zonation attributes such as seasonal water table fluctuation and vegetation dynamics. A final section of papers look at river corridors and ecosystem health.

The editors particularly wish to thank Dr Lucy Bolton for her assistance with putting together this volume.