Dj. Giberson et D. Caissie, STREAM HABITAT HYDRAULICS - INTERANNUAL VARIABILITY IN 3 REACHES OF CATAMARAN BROOK, NEW-BRUNSWICK, Canadian journal of fisheries and aquatic sciences, 55(2), 1998, pp. 485-494
The hydraulic habitat of 12 sites in a small salmon stream in central
New Brunswick was investigated between 1992 and 1995 to determine patt
erns of habitat (substrate) stability between and within reaches. Stab
ility was evaluated by measuring particle size distribution in replica
ted erosional and depositional sites in each reach and calculating the
proportion of the bed predicted to be in motion at given flood flows.
Erosional (riffle) sites in all reaches showed significant difference
s (ANOVA, p < 0.05) in substrate particle sizes from year to year, mov
ement of embedded sediment samplers, and high predicted bedload meveme
nt, even in small spates. In contrast, depositional sites (flats, some
runs) appeared stable, showing no significant year-to-year difference
s in particle sizes, no movement of embedded samplers, and no increase
in predicted bedload movement until high flow. The impact of the floo
d on the streambed depends heavily on the particle size distribution p
resent during the flood, resulting in different levels of substrate di
sturbance during equal-magnitude floods in different years. Certain si
tes (e.g., flats) may be able to serve as hydraulic refugia to stream
fauna during some floods. It is clear that year-to-year variations in
substrate stability must be considered when evaluating habitat stabili
ty for stream fauna.