Discussion
The results of this study indicate the introduction of a channel
occlusion and the subsequent hydrologic and geomorphic responses of the
riverscape have initiated expansive, positive changes to habitat
diversity. Prior research identified that valley plugs can have negative
ecosystem implications including various land-use challenges and
alterations to both floodplain and sedimentation dynamics (Shields Jr.,
Knight, & Cooper, 1999; Pierce & King 2008; Fore, Alford, Blackwood,
& Blanchard, 2019); however, we observed that in the SRR, the valley
plug has facilitated a positive return to near-historic conditions.
Accounts of the SRR valley during the early 20th century describe
abundant cottonwoods, willows, sedges, and wetlands suggesting the water
table was near the surface in much of the valley, similar to what we
have seen over the past decade with the evolution of the valley plug
(Fortney et al., 2011). Early surveys of the lower SRR also observed a
highly sinuous, braided system with multiple low flow channels within
the wide active channel (Fortney et al., 2011). Taking these early
observations into account, we conclude the conditions surrounding the
valley plug are very similar to the historic late 19thand early 20th century condition of the SRR, where the
river has shifted from a Stage III degraded riverscape to the
anastomosing grassed wetland or Stage 0, of the nine-stage Stream
Evolution Model identified by Cluer and Thorne (2014).