HR: 14:40h
AN: H33F-05    [Abstracts]
TI: Glacially-Induced Scaling Relations in Mountain Drainage Basins
AU: * Brardinoni, F
EM: fbrardin@geog.ubc.ca
AF: The University of British Columbia, Department of Geography, 1984 West Mall, Vancouver, BC V6T1Z2 Canada
AB: River networks define specific scaling relations in the landscape. Accordingly, contributing area scales with local slope gradient controlling geomorphic process domains hence rates of erosion; and channel-reach hydraulic geometry and morphology. In currently glaciated environments ice flows possess peculiar geomorphic erosion and transport laws which likely disturb pre-glacial landscape structure and superimpose "glacial" scaling dependences. On such premise, it is hypothesized that formerly glaciated environments currently exhibit transient scaling dependences that deviate significantly from those documented in unglaciated analogs. Study sites are drawn from the Coast Mountains of British Columbia. Results show direct spatial scale linkages and generalized departure from unglaciated scaling relations at all levels. Glacial macro-forms, by imposing local channel gradient and degree of colluvial-alluvial coupling, affect the spatial distribution of process domains, which in turn control channel-reach morphology and hydraulic geometry. In particular, morphometric characteristics of relict glacial troughs introduce a peculiar colluvial-alluvial transition trend in the area-slope space. Hanging valleys, which enclose purely alluvial riffle-pool reaches separate strongly-coupled colluvial reaches located both up- and down-stream. Transitions across process domains tend to reset downstream trends of channel width, depth, and D₉₅. Exponents of area-width and area-depth relations deviate significantly from 0.5 and 0.33. Specifically, colluvial channels exhibit higher downstream channel widening, while fluvial reaches denote negative (downstream narrowing) or nearly null exponents. To model channel width, a Manning-based expression, which expresses roughness as a function of D₉₅, is applied. Complex channel-width trends that were measured in the field are described reasonably well. Channel width in colluvial reaches is consistently underestimated. The stepped topography of glaciated landscapes appears to be an ideal natural laboratory to study how channel geometry and morphology respond to a wide range of imposed slope gradients and sediment supply.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1819 Geographic Information Systems (GIS)
DE: 1879 Watershed
SC: Hydrology [H]
MN: Fall Meeting 2005