ABSTRACT
The last few decades have seen increasing interest in enhancing, restoring, and protecting the ecology of wetlands, streams, and watersheds. Achieving these goals requires sound fundamental and applied knowledge, close interaction between scientists and engineers, a systems approach, and a good understanding of spatial and temporal scales. This entry addresses the role and importance of an active floodplain in wadeable two-stage stream systems where the active floodplain plays an important role in sustaining or establishing dynamic equilibrium. Specifically, focus is placed on the size and geometry of the active floodplain (Stage 2) relative to the size of a main channel (Stage 1) that is shaped by channel-forming discharges (Fig. 1). Consideration is also given to floodplains for modified streams and constructed channels such as agricultural ditches. The goal of this entry is to aid the reader in understanding the hydrology, hydraulics, and geomorphology of these systems and to then use this knowledge to protect or size a self-sustaining two-stage channel system.
