A global perspective on denudation data, primarily specific sediment yield in mountainous regions

Abstract

A brief review of the evolution of denudation research since the 1960s is followed by a review of specific sediment yield variability in mountainous regions of the world as a function of spatial scale, relief, glaciation, lithology and disturbance type and location within the basin. A general model of scalar relations of suspended sediment yield for Canadian regions warns against comparing data from basins with areas ranging over several orders of magnitude. A regional summary of specific sediment yield in mountainous British Columbia confirms that in basins <1 km2 and >30,000 km2 specific sediment yield decreases with basin size whereas in basins of intermediate size (between 1 km² and 30,000 km²) specific sediment yield increases with basin size. This effect is interpreted in terms of three distinct process zones in every mountain basin. These zones can be characterized as a) generally degrading hillslope zones, b) generally aggrading footslopes and valley sides, and c) channelized flows on valley floors demonstrating either net aggradation or degradation. These are identifiable repeating elements in such landscapes. Suspended sediment yield data from mountainous regions around the world are considered in light of the British Columbia model. Some support for the model is found where basins are stratified according to scale, relief, lithology, disturbance types, and location within each basin. Disturbance types include the presence of glaciers, land use activities of various kinds, such as increasing population pressure in the intertropical montane zone, changing population distribution and associated economic activities in the temperate montane zone, and potentially hydroclimate change.