THE SERIAL DISCONTINUITY CONCEPT - EXTENDING THE MODEL TO FLOODPLAIN RIVERS

The serial discontinuity concept (SDC) was developed as a theoretical construct that views impoundments as major disruptions of longitudinal resource gradients along river courses. According to the SDC, dams result in upstream-downstream shifts in biotic and abiotic patterns and processes; the direction and extent of the displacement depend on the variable of interest and are a function of dam position along the river continuum. As originally formulated, the SDC did not consider interactions between the river and its flood plain. The new perspective presented herein is an initial attempt to encompass the dynamics of alluvial flood plain rivers into the model using a three reach characterization: constrained headwater reach, braided reach and meandering reach. The constrained headwater reach has conditions similar to those described in the original SDC, but the braided and meandering reaches provide a perspective that was not addressed in the model. Lateral interactions between the channel and the flood plain are critical to a holistic understanding of natural river ecosystems and the alterations induced by regulation. The fringing flood plain, with its diverse water bodies and alluvial forest mosaic, is considered an integral part of the river system.