TY - JOUR
T1 - Evolution of a foredune and backshore river complex on a high-energy, drift-aligned beach
AU - Heathfield, Derek K.
AU - Walker, Ian J.
N1 - Funding Information:
This research was funded in part by an NSERC Discovery Grant (Application 238751-2011 ) to IJW and logistical support from Parks Canada Agency — Pacific Rim National Park Reserve. Special thanks for field assistance and/or data sharing are extended to H. Beaugrand, M. Collyer, I. Darke, and J. Eamer. Figure support thanks to O. Heggen and D. Shugar. Helpful suggestions on earlier drafts of this paper were also provided by two anonymous reviewers, D. Atkinson, R. Davidson-Arnott, and A. Plater.
PY - 2015/11/1
Y1 - 2015/11/1
N2 - This paper examines the multi-decadal evolution of a foredune and backshore river complex on a wave-dominated, drift-aligned coast at Wickaninnish Bay on southwestern Vancouver Island, British Columbia, Canada. Local shoreline positions are generally prograding seaward as fast as +1.46ma-1 in response to rapid regional tectonic uplift and positive onshore sediment budgets. The northern end of the foredune system has extended rapidly alongshore in response to net northward littoral drift. Despite these net accretional responses, the beach-dune system experiences relatively frequent (return interval ~1.53years) erosive events when total water levels exceed a local erosional threshold elevation of 5.5m above regional chart datum. Geomorphic recovery of the beach-dune system from erosive events is usually rapid (i.e., within a year) by way of high onshore sand transport and aeolian delivery to the upper beach. This response is complicated locally, however, by the influence of a backshore river that alters spatial-temporal patterns of both intertidal and supratidal erosion and deposition. Historic landscape changes and rates of shoreline positional change are derived from several years of aerial photography (1973, 1996, 2007, 2009, 2012) using the USGS Digital Shoreline Analysis System (DSAS). Significant volumetric changes are also estimated from aerial LiDAR-derived DEMs in 2005, 2009 and 2012, and related morphodynamics are interpreted using a statistically constrained geomorphic change detection method. Results suggest that supratidal bar development, overwash deposition and aeolian deposition on a low-lying supratidal platform, combined with alongshore extension of the foredune complex, is forcing Sandhill Creek to migrate northward in the direction of beach drift. In response, the river actively erodes (-1.24ma-1) a bluff system landward of the channel, which generates substantial sediment volumes (-0.137m3m-2a-1) that feed a large intertidal braided channel and delta system. These local responses provide context for a conceptual model of the evolution of a wave-dominated, drift-aligned beach-foredune system that interacts with a backshore river. This model may provide useful information to local park managers as erosion and sedimentation hazards threaten visitor safety and park infrastructure.
AB - This paper examines the multi-decadal evolution of a foredune and backshore river complex on a wave-dominated, drift-aligned coast at Wickaninnish Bay on southwestern Vancouver Island, British Columbia, Canada. Local shoreline positions are generally prograding seaward as fast as +1.46ma-1 in response to rapid regional tectonic uplift and positive onshore sediment budgets. The northern end of the foredune system has extended rapidly alongshore in response to net northward littoral drift. Despite these net accretional responses, the beach-dune system experiences relatively frequent (return interval ~1.53years) erosive events when total water levels exceed a local erosional threshold elevation of 5.5m above regional chart datum. Geomorphic recovery of the beach-dune system from erosive events is usually rapid (i.e., within a year) by way of high onshore sand transport and aeolian delivery to the upper beach. This response is complicated locally, however, by the influence of a backshore river that alters spatial-temporal patterns of both intertidal and supratidal erosion and deposition. Historic landscape changes and rates of shoreline positional change are derived from several years of aerial photography (1973, 1996, 2007, 2009, 2012) using the USGS Digital Shoreline Analysis System (DSAS). Significant volumetric changes are also estimated from aerial LiDAR-derived DEMs in 2005, 2009 and 2012, and related morphodynamics are interpreted using a statistically constrained geomorphic change detection method. Results suggest that supratidal bar development, overwash deposition and aeolian deposition on a low-lying supratidal platform, combined with alongshore extension of the foredune complex, is forcing Sandhill Creek to migrate northward in the direction of beach drift. In response, the river actively erodes (-1.24ma-1) a bluff system landward of the channel, which generates substantial sediment volumes (-0.137m3m-2a-1) that feed a large intertidal braided channel and delta system. These local responses provide context for a conceptual model of the evolution of a wave-dominated, drift-aligned beach-foredune system that interacts with a backshore river. This model may provide useful information to local park managers as erosion and sedimentation hazards threaten visitor safety and park infrastructure.
KW - Bluff
KW - Coastal erosion
KW - Drift-aligned
KW - Foredune
KW - LiDAR
KW - River
KW - Wave-dominated
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U2 - 10.1016/j.geomorph.2015.08.006
DO - 10.1016/j.geomorph.2015.08.006
M3 - Article
AN - SCOPUS:84941308792
SN - 0169-555X
VL - 248
SP - 440
EP - 451
JO - Geomorphology
JF - Geomorphology
ER -