Beach-dune morphodynamics and climate variability impacts of Wickaninnish Beach, Pacific Rim National Park Reserve, British Columbia, Canada




Beaugrand, Hawley Elizabeth Ruth

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To date, there has been little research on the morphodynamics of Canada’s Pacific mesotidal beach-dune systems and their potential response to climate variability and change. Accordingly, this study examines and characterizes the morphodynamics of a mesotidal beach-dune system on western Vancouver Island (Wickaninnish Beach) and investigates its potential response to extreme seasonal storms, climate variability events, and climate change trends. This research also informs protected areas management approaches, whose effectiveness is important to the conservation of early successional and proportionately rare specialized dune species. Research methods include repeat cross-sectional surveys, repeat vantage photographs, and analysis of the wind, wave, and water level regime. Both the regional wind regime and aeolian sediment transport regime are bimodal, with a WNW (summer) component and a SE (winter) component. The nearshore littoral sediment transport regime is characterized by both longshore and rip cell circulation cells. To date, survey results are informative only of seasonal changes. Longer-term monitoring will better reveal contemporary trends of the beach-dune system. A high dune rebuilding potential (aeolian sand transport potential = 9980 m3 m‐1 a‐1, resultant aeolian sand transport = 3270 m3 m‐1 a‐1 at 356 degrees) was found based on the incident wind regime and sand grain diameter. A threshold elevation for dune erosion was defined at 5.5 m aCD. Erosive water levels were analyzed using three approaches yielding the following results. Erosive water levels are reached on average, ~3.5 times per year; with a probability of 65% in any given year; and, annual return levels are 5.59 m aCD, suggesting erosive water levels are reached annually. Statistical relations show that the positive phase of El Niño Southern Oscillation (ENSO) (El Niño) shares the most variance with the incident oceanographic regime (e.g., significant wave height, peak period), and although a causal relationship cannot be drawn, El Niño may contribute to the occurrence of erosive events on Wickaninnish Beach. Beyond El Niño, overall findings suggest climate variability signals are manifest in regional erosional water level regimes.



climate variability, Wickaninnish Beach, Pacific Rim National Park, coastal erosion, dune, beach