Glacial erosion, evolution of river long profiles, and the organization of process domains in mountain drainage basins of coastal British Columbia

Abstract

[1] In glaciated British Columbia, Canada, Quaternary climate changes are responsible for profound spatial reorganization of Earth surface processes. These changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs. The evolution of glaciated landscapes is examined by analyzing the structure of geomorphic process domains and channel long profiles. To identify process domains we use channel surveys and GIS analysis to construct slope-area transects of the channel network. This analysis reveals generalized process-form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains. At the landscape scale of ''source'' colluvial channels (contributing area <1 km 2 ), the glacial/paraglacial signature commonly overrides that produced by contemporary debris flows. Along the axis of former ice flows, relict glacial cirques introduce a ''hanging'' fluvial domain at contributing areas as small as 8 Â 10 À2 km 2 and produce complex channel long profiles similar to those observed for rivers responding to tectonic forcing. Slope-area relations typical of unglaciated equilibrium environments do not apply here. The concept of process domains appears to hold, however, some major glacially forced modifications in the alluvial-colluvial transition are observed and the definition of a depositional colluvial subdomain is proposed. Comparison between field-and GIS-measured slopes reveals that GIS-associated error is not uniform between process domains, and that GIS-based plots do not successfully discriminate field-based process domains. The combination of glacial and post-glacial fingerprints and the effects of ongoing Earth surface processes generate a complex landscape whose glacial signatures may persist until the onset of the next ice age.Citation: Brardinoni, F., and M. A. Hassan (2006), Glacial erosion, evolution of river long profiles, and the organization of process domains in mountain drainage basins of coastal British Columbia,

Criteria to Distinguish Between Periglacial, Proglacial and Paraglacial Environments

“…The search for a metric Brardinoni & Hassan (2006) have explored the use of geomorphic process domains to locate the degree of recovery from glaciation of mountain landscapes.…”

Bumps in river profiles: uncertainty assessment and smoothing using quantile regression techniques

“…The geometry of a river, specifically its longitudinal profile, reflects climatic and tectonic forcing, variations in base level and sediment transport processes, and differences in bedrock erodibility. Gradients along rivers, for example, reflect spatial variations in uplift rates (Whipple et al, 2013;Mudd et al, 2014;Scherler et al, 2014) and indicate the extent of past glaciations (Brardinoni and Hassan, 2006). Moreover, they can act as predictors for the zones of erosion and sediment accumulation during extreme events (Devrani et al, 2015) and reflect the repeated impact of mass-wasting events (Korup, 2006).…”

Topographic signature of debris flow dominated channels: implications for hazard assessment

“…Ijjasz-Vasquez and Bras [8]), and provided field evidence of the dominance of debris flows in headwater channels (e.g. Stock and Dietrich [9]; Stock et al [10]; Brardinoni and Hassan [11]). Accordingly, area-slope diagrams have been extensively used to define the morphometric extent of process domains, which are defined as regions where sediment transfer is controlled by one dominant geomorphic process (e.g.…”