Freshwater systems are among the most biologically diverse and rich systems in the world (Decamps, 1997; Master et al., 1998). This richness and diversity is in large part a result of the highly dynamic nature of river systems which creates a mosaic of shifting habitat types that vary in age, species composition, and structure and provide a broad range of natural conditions around which the life cycles of species and natural communities have evolved (Ward et al., 2002).

Since the rich and unique biodiversity values of rivers are related to the dynamic nature of these systems, effective river conservation must include the protection of key physical and ecological processes. These processes are driven in large part by the movement of water and the associated movement of sediment, energy, materials and organisms. They are also driven by energy inputs to these systems, including the contribution of organic and other materials that provide the foundation on which the web of life within these systems is built.

River health depends on a wide array of processes that require dynamic interaction between the water and land through which it flows. The areas of dynamic connection and interaction provide a frame of reference from which to conserve, restore and manage river systems. We choose the term active river area to define this framework. “Active” indicates the dynamic and disturbance-driven processes that form and maintain river and riparian systems and their associated habitats and habitat conditions. “River area” represents the lands that contain both of aquatic and riparian habitats and those that contain processes that interact with and contribute to a stream or river channel. The active river area framework offers a more holistic vision of a river than solely considering the river channel as it exists in one place at one particular point in time. Rather, the river becomes those lands within which the river interacts both frequently and occasionally.

The active river area provides a systematic means for conceptualizing and protecting the river as a dynamic system with a broad range of conditions that are typical of natural river systems. The active river area is spatially explicit and can be readily identified – narrow in some areas, wider in others – and captures the living, dynamic processes and places that define these systems. The active river area includes a number of distinct components, which provide specificity to guide actions for protection, restoration and management.