Understanding the temporal dynamics of the wandering Renous River, New Brunswick, Canada

Wandering rivers are composed of individual anabranches surrounding semi-permanent islands, linked by single channel reaches. Wandering rivers are important because they provide habitat complexity for aquatic organisms, including salmonids. An anabranch cycle model was developed from previous literature and held observations to illustrate how anabranches within the wandering pattern change from single to multiple channels and vice versa over a number of decades. The model was used to investigate the temporal dynamics of a wandering river through historical case studies and channel characteristics from field data. The wandering Renous River, New Brunswick, was mapped from aerial photographs (1945, 1965, 1983 and 1999) to determine river pattern statistics and for historical analysis of case studies. Five case studies consisting of a stable single channel, newly formed anabranches, anabranches gaining stability following creation, stable anabranches, and an abandoning anabranch were investigated in detail. Long profiles, hydraulic geometry, channel energy, grain size and sediment mobility variables were calculated for each channel. Within the Renous study area, the frequency of channel formation and abandonment were similar over the 54 years of analysis, indicating that the wandering pattern is being maintained. Eight anabranches were formed through avulsions, five were formed through the emergence of islands from channel bars and 11 anabranches were abandoned. The stable anabranch pair displayed similar hydraulic geometry and channel energy characteristics, while unstable anabranch pairs did not. The anabranch pair that gained stability displayed more similar channel energy characteristics than the anabranch pair that was losing stability (abandoning). It appears that anabranch pairs with similar energy characteristics are more stable than anabranches where these characteristics are out of balance. This is consistent with the hypothesis that anabranch pairs of similar length will be more stable than those with dissimilar lengths. Copyright (c) 2005 John Wiley & Sons, Ltd.