REGIONAL SETTING AND CONTROLS ON PATTERN CHARACTERISTICS OF WANDERING MIRAMICHI SALMON RIVERS, NEW BRUNSWICK, CANADA

Side-channels within wandering rivers provide important habitat for salmonids on the Pacific and Atlantic coasts of North America. On the Pacific coast, side-channels provide refuge from high velocities in main-channels during winter high flows. On the Atlantic coast, side-channels provide over-wintering habitat for adult salmon and may provide refuge from heat stress for juveniles. Wandering rivers are composed of multiple channel sections surrounding semi-permanent islands, linked by single channel sections. The formation of wandering rivers has been associated with high sediment input from neoglacial moraines, however wandering rivers within the Miramichi region of New Brunswick are not associated with high sediment input. This study investigated the regional setting of wandering rivers within the Miramichi drainage basin and controls on the pattern characteristics of these rivers.

Wandering rivers within the Miramichi region occurred within larger valleys located downstream of a regional change in bedrock. On a slope-discharge plot, Miramichi wandering rivers plotted in the same range but lower than other wandering rivers and displayed a similar range of specific stream power values. Icejams are common within Miramichi rivers and trigger avulsions that create side-channels. Three factors are needed to form wandering rivers: (1) wide valleys, (2) channel energy levels between braiding and meandering, and (3) avulsion triggers.

A Pearson correlation matrix and principal component analysis were used to explore relationships among river pattern variables. Larger rivers within the Miramichi displayed greater anabranching intensity than smaller rivers. Larger rivers appear to produce higher icejams that create more avulsions and maintain channels that may otherwise be abandoned, thereby creating greater anabranching intensity.

To protect side-channel habitat within wandering rivers, naturally occurring avulsion triggers, such as icejams or terrace erosion, should be allowed to occur. Within regulated rivers, icejams or open water floods may be created to trigger avulsions, producing side-channels. Abandoned channels should not be infilled or blocked to provide future avulsion sites and habitat.