Physiographically controlled allometry of specific sediment yield in the Canadian Cordillera: A lake sediment-based approach

It is generally supposed that specific sediment yield declines as the drain age basin area increases, as part of the mobilized sediment becomes trapped in the downstream cascade of storage zones. In British Columbia, using flu vial suspended sediment load data, Church and Slaymaker(Nature 1989, Vol 33 7, pp. 452-454) have observed a pattern of increasing specific sediment yie ld at all spatial scales up to 3x10(4) km(2). This trend has been attribute d to the dominance of secondary remobilization of Quaternary sediments over primary denudation of the land surface. Using a larger data set of lake se diment-based estimates of long-term sediment yield, sub-regional patterns o f specific yield have been investigated for the Canadian Cordillera. Betwee n spatial scales of 0.9 and 190 km(2) sediment yield trends are differentia ted by physiography, as indicated by the variable allometry observed in the specific sediment yield-drainage basin area relations. Highest sediment yi elds were observed in the Coast Mountains where specific sediment yields co nform to the regional pattern described by Church and Slaymaker. However, i n flat-lying plateau and major valley areas specific sediment yield decreas es with increasing drainage area, thus conforming to the conventional model of sediment delivery. In several other subregions of intermediate relief t here were no significant relations between specific yield and drainage area . These results suggest that no single model of sediment yield is adequate to describe sediment transfer processes in the Canadian Cordillera at the s ub-regional scale.