A dendrochronological investigation of paraglacial activity and streamflow in the vicinity of the Homathko Icefield, British Columbia coast mountains, Canada




Hart, Sarah J.

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Moraine and glacier dams bordering the Homathko Icefield burst in the 1980s and 1990s, causing catastrophic downstream floods. The largest of the floods occurred in August 1997 and was caused by rapid breaching of the dam that impounds Queen Bess Lake, below Diadem Glacier. The outburst flood from the lake eroded the Holocene-age sediment fill in the valley below, exposing a series of subfossil forest layers separated by overbank floodplain sediments. A field investigation of the eroded valley fill in 2008 revealed multiple paraglacial valley-fill units, many of which are capped by in situ stumps and woody detritus. Dendrogeomorphic dating and stratigraphic evidence revealed six major sediment deposition events that coincide with regional, independently dated glacier episodes over the past 1200 years. Construction of tree-ring chronologies for the study area also allowed for the examination of the relationship between radial tree growth and hydroclimate. Dendroclimatological and dendrohydrological techniques were used to reconstruct summer stream discharge of nearby Chilko River. An Engelmann spruce tree-ring chronology provided a proxy for mean summer discharge of Chilko River for the period 1775-2007. This record is the first to be developed from tree-ring data for a river draining a glacierized watershed in the British Columbia Coast Mountains. This proxy record provides insights into streamflow variability of a typical Coast Mountains river over the past 232 years and confirms the long-term influence of the Pacific Decadal Oscillation and El Niño-Southern Oscillation teleconnections on hydroclimatic regimes in the region.



Coast Mountains, paraglacial, tree-rings, Homathko Icefield, British Columbia, streamflow, Chilko River, dendrochronology