Channel Form Adjustment in Supraglacial Streams, Austre Okstindbreen, Norway

Abstract

Despite rapidly changing surface conditions, supraglacial streams are shown to be capable within limits of adjusting their beds in such a way as to develop and maintain characteristic forms. The most consistent variation of bed topography occurs in a perennial stream with a more stable base-level and meandering planform, a variation which is concentrated in the riffle-pool waveband of alluvial rivers and which persists despite more than 1 m of surface ablation. Analyses of cross-sectional form along the same stream reveal that some but not all parameters vary systematically. Mean depth and width-depth ratio differ significantly between pool and step sections, while those parameters together with an asymmetry index fluctuate at a wavelength commonly associated with meandering. High velocities undoubtedly contribute to the rapidity of adjustment and to the transport of ice crystals (size range of 2 to 32 mm) carried as saltating bed load or in suspension. The characteristics of transport suggest that it is supply- rather than capacity-limited.