Morphodynamics of dune erosion and rebuilding on macrotidal beaches of British Columbia

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This research examines the sedimentary and geomorphic responses of high-energy, forested and driftwood lined beach-dune systems on BC's north coast. These systems are distinct from others in Canada for extreme wind, wave & tide regimes and for different anthropogenic & ecological factors (e.g., driftwood jams, rapidly colonizing vegetation) that control their form and function. These systems are also sensitive to known climate variability signals of the NE Pacific such as El Nino and the Pacific Interdecadal Oscillation (PDO) and do not experience winter season effects such as sea ice, frozen ground or vegetation declines like other systems on the Great Lakes or in Atlantic Canada. The main objective is to measure and model the relations between near-surface airflow, surface roughness and sediment transport so as to enhance knowledge on how these systems respond to coastal erosion (via wave action) and subsequent rebuilding (via aeolian sand transport). Regional ocean-atmosphere processes drive beach-dune morphodynamics by controlling the local frequency & magnitude of erosive water levels and dune rebuilding via onshore aeolian (wind) sand transport. Longer-term geomorphic responses and potential changes in the erosion-rebuilding regime will be related to climate variability & change events. To do this, 3 research hypotheses will be explored. First, tide stage & wind direction affect beach-dune dynamics via a 'fetch' effect that controls the amount of sand delivered to the beach. This hypothesis is the basis of a recent theoretical model that will be tested with field data. Second, driftwood jams & forest stands provide additional roughness & storage capacity to trap windblown sand on beaches.  These features provide a buffer against extreme water levels & wave attack and can create new dunes. Third, climate variability events affect wind, wave & water level regimes and can be correlated to seasonal to interannual morphological responses of coastal dunes. It follows that local-scale dynamics of coastal erosion and dune rebuilding are related to climate variability & change.