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

这项研究考察了不列颠哥伦比亚省北海岸高能、森林和漂流木材排列的海滩沙丘系统的沉积和地貌响应。这些系统与加拿大的其他系统不同，因为极端的风、浪和潮汐制度，以及控制它们形式和功能的不同人为和生态因素(例如，浮木堵塞、迅速定居的植被)。这些系统对已知的东北太平洋气候变化信号也很敏感，如厄尔尼诺和太平洋年代际涛动(PDO)，不会像五大湖或加拿大大西洋上的其他系统那样经历冬季影响，如海冰、冻土或植被衰退。其主要目标是对近地表气流、地表粗糙度和泥沙输送之间的关系进行测量和建模，以便增进关于这些系统如何应对海岸侵蚀(通过波浪作用)和随后的重建(通过风沙输送)的知识。区域海洋-大气过程通过控制局部侵蚀水位的频率和大小，以及通过风沙输送来重建沙丘，从而驱动了海滩-沙丘地貌动力学。较长期的地貌反应和侵蚀重建制度的潜在变化将与气候变化和变化事件有关。要做到这一点，将探索3个研究假设。首先，潮汐阶段和风向通过控制沙子输送到海滩的沙量来影响海滩沙丘的动态。这一假设是最近一个理论模型的基础，该模型将用现场数据进行验证。其次，浮木堵塞和森林林提供了额外的粗糙度和储存能力，可以将风沙困在海滩上。这些功能提供了缓冲，抵御极端水位和海浪的攻击，并可以形成新的沙丘。第三，气候变率事件影响风、浪和水位的变化，并与沿海沙丘的季节和年际形态响应相关。由此可见，局部尺度的海岸侵蚀和沙丘重建动态与气候变异性和变化有关。

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.