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

这项研究探讨了沉积和地貌的高能量，森林和浮木内衬海滩沙丘系统在BC省的北海岸的反应。这些系统与加拿大的其他系统不同，因为极端的风、波浪和潮汐状况以及不同的人为和生态因素（例如，浮木堵塞，迅速殖民植被），控制他们的形式和功能。这些系统也对东北太平洋的已知气候变率信号敏感，如厄尔尼诺和太平洋年代际振荡（PDO），并且不像五大湖或加拿大大西洋沿岸的其他系统那样经历冬季影响，如海冰，冻土或植被衰退。主要目的是测量近地表气流、地表粗糙度和沉积物输运之间的关系并建立模型，以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（通过风成沙输运）的知识。区域海洋-大气过程通过控制当地侵蚀水位的频率和幅度以及通过陆上风成（风）沙输送的沙丘重建来驱动海滩沙丘形态动力学。长期地貌反应和潜在的变化，在侵蚀重建制度将与气候变异性和变化事件。为此，将探讨三个研究假设。首先，潮汐阶段和风向影响海滩沙丘动力学通过一个“取”的效果，控制输送到海滩的沙子的量。这一假设是最近的一个理论模型的基础，将与现场数据进行测试。其次，浮木堵塞和森林看台提供额外的粗糙度和存储能力，以捕获海滩上的风沙。 这些特征提供了抵御极端水位和波浪攻击的缓冲，并可以形成新的沙丘。第三，气候变率事件影响风，波和水位制度，并可以与季节到年际的沿海沙丘的形态响应。因此，海岸侵蚀和沙丘重建的局部尺度动力学与气候变率和变化有关。

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.