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 manuscript 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. A floodplain ratio (FPR) is used to evaluate different active floodplain widths. The FPR is the ratio of the floodplain width, when the channel-forming discharge is exceeded, divided by the top width of the channel when this discharge occurs. Ideally, active floodplains should have FPRs greater than 5 though smaller floodplains will have some beneficial influences on the sustainability of channel systems. The approaches described in this article are relatively simple and represent a minimum level of analysis that should be performed if modifications or protection strategies are proposed for a stream system. This chapter is not intended as a guide to restoration.
