Assessing impacts of anthropogenic large woody debris and dynamic restoration on beach-dune morphodynamics and resilience in Pacific North America

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Coastal dunes are rare globally and provide key ecosystem services such as habitat for endangered species, sites of high tourism value, groundwater recharge and protection against coastal erosion and sea-level rise. In British Columbia, these systems are rare (<5% of the coast) and distinct due to: 1) extreme wind, wave and water level regimes; 2) sensitivity to climatic variability signals (El Niño-La Niña; Pacific Decadal Oscillation) and 3) lack of nival effects (snow, shore-fast ice). In Pacific North America, there are two common anthropogenic alterations that affect beach-dune form and function on undeveloped coasts - large woody debris (LWD, mostly historic logging refuse) and invasive vegetation (introduced to stabilize dunes). Research on both is limited, impacts are substantial and management responses are underway, such as 'dynamic' restoration projects that restore geomorphic processes and native plant communities in compliance with federal legislation (e.g. Canadian Species at Risk Act, US Endangered Species Act). The long-term goals of the proposed program are to transform understanding on how LWD (Focus 1) and dynamic restoration to remove invasive plants (Focus 2) affect beach-dune morphodynamics, sediment budgets, and resilience to coastal erosion, climatic variability impacts and sea-level rise. In turn, this will provide useful information for ongoing coastal management and ecosystem restoration efforts. The program builds on established partnerships with management agencies at 3 study sites: 1) Parks Canada-Pacific Rim National Park, Tofino BC; 2) US Fish & Wildlife Service-Humboldt Bay Wildlife Refuge, Arcata CA; and 3) BC Parks & the Hakai Institute, Calvert Island, BC. As such, the program is collaborative and presents excellent HQP training opportunities. Focus 1 will quantify the impacts of LWD on beach-dune sand transport, morphodynamics and landscape evolution (foredune growth, dune migration, erosion-recovery cycles, shoreline progradation/retrogradation). Focus 2 will assess the effectiveness of various restoration treatments that remove invasive vegetation, stimulate dynamic geomorphic processes and re-establish native plant communities. Both foci will use leading-edge technologies and methods to conduct event-based experiments coupled with detailed terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) surveys to measure sand transport, erosion/deposition patterns and sediment volume changes. These data will complement high-res time-lapse photogrammetry (TLP) and GIS analyses of historic aerial photos of study sites to quantify and interpret seasonal to interannual impacts of these alterations on dune resilience to natural (e.g. erosive water levels) and artificial (e.g. vegetation removal) disturbance events with direct relevance for land management and development of climate change adaptation strategies.