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

Abstract

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 field 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.

Stability, morphology and surface grain size patterns of channel bifurcation in gravel–cobble bedded anabranching rivers

“…Within the larger neighbouring Main Southwest Miramichi River, break-up occurs between 22 March and 2 May; the average break-up date is 14 April (Allen and Cudbird, 1971). Ice jams are common in the Miramichi basin of New Brunswick (Beltaos et al, 1989) and may form downstream of avulsion sites to force water over floodplains to reoccupy abandoned channels (Burge and Lapointe, 2005). On the Little Southwest Miramichi River, large ice jams occur every second year on average, obtaining a depth of 1 m above the floodplain (Burge, 2005).…”

Evolution of Early Pleistocene fluvial systems in central Poland prior to the first ice sheet advance – a case study from the Bełchatów lignite mine

“…A relatively high-energy channel coexisted with the floodplain where silt settled in oxbows evolving to mires with peat accretion. These features allow to interpret the sedimentary environment as a wandering river, i.e., a fluvial system transitional between the meandering and braided end members (Miall, 1996;Burge & Lapointe, 2005). Significantly, wandering rivers frequently develop in catchments with extensive vegetation cover (Nanson & Knighton, 1996;Beechie et al, 2006).…”

Biophysical Characterisation of Fluvial Corridors at Reach to Network Scales

“…When several image series are available, it is possible to observe changes in channel planimetry or channel pattern on annual to decadal timescales (Odgaard, 1987;Piégay et al, 1997;Gurnell, 1997;Gilvear et al, 2000;Winterbottom, 2000;Burge and Lapointe, 2005;Zanoni et al, 2008;etc.). It is also possible to predict discharge from water flow area, notably when water surface width is particularly sensitive to discharge change, which is the case of wandering or braided rivers.…”