Downstream‐propagating channel responses to decadal‐scale climate variability in a glaciated river basin

Journal of Geophysical Research: Earth Surface
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Abstract

Regional climate is an important control on the rate of coarse sediment mobilization and transport in alpine river systems. Changes in climate are then expected to cause a cascade of geomorphic responses, including adjustments in downstream channel morphology. However, the mechanics and sensitivity of channel response to short‐term climate variability remain poorly documented. In the Nooksack River, which drains a glaciated stratovolcano in Washington State, bed elevation changes were inferred from shifting stage–discharge relations at seven USGS stream gages. Decadal‐scale elevation trends at most sites can be explained as a downstream‐propagating channel response to regional climate variability, where periods of persistent warm, dry [cool, wet] conditions corresponded to periods of aggradation [incision]. The channel elevation response propagated downstream at a rate of one to four kilometers per year; propagation rate scaled closely with channel slope. Historical trends in glacier extent and flood intensity both show some potential to explain climate–sediment linkages, though assessing causation is complicated by the shared climate signal in both records. Results show the influence of the Pacific Decadal Oscillation, with relatively high coarse sediment yields prior to 1950 and since 1980, and notably lower sediment yields from 1950 to 1980. Measured sediment yields from nearby glaciated basins corroborate this history, suggesting a regional coherence to these climate–sediment linkages. These results document consistent relations between climate, sediment supply and downstream channel response at the basin‐scale, with channel responses propagating downstream over periods of decades with little apparent attenuation.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Downstream‐propagating channel responses to decadal‐scale climate variability in a glaciated river basin
Series title Journal of Geophysical Research: Earth Surface
DOI 10.1029/2018JF004734
Volume 124
Issue 4
Year Published 2019
Language English
Publisher AGU
Contributing office(s) Washington Water Science Center
Description 18 p.
First page 902
Last page 919
Country United States
State Washington
Other Geospatial Nooksack River