AbstractWoody debris is ubiquitous in coastal waters, and on shorelines proximate to forested regions. Logs and driftwood play a vital role in coastal and global ecosystems, and can provide valuable data to support studies of oceanography, geomorphology, ecology, history and archaeology. There is growing interest in the role that woody debris can play in nature-based coastal engineering solutions. However, large quantities of woody debris in coastal waters can pose significant hazards to communities, infrastructure, navigation and ecosystems. Thus, the changing abundance and distribution of coastal driftwood, driven by factors including human activities and climate change, has potential for both positive and negative consequences. A better understanding of coastal driftwood fate and transport processes is needed to inform management practices, uses, and sustainable ecosystem management. To date, research on physical transport of woody debris, has been concentrated on tsunami and inland (riverine) environments, where spatiotemporal scales and driving processes are significantly different from typical climatic or even extreme (storm) conditions in coastal waters. In this paper, we describe a series of scale physical model experiments, conducted to provide insight to debris transport processes in coastal waters under a range of controlled wave and water level conditions. The experiments were conducted in a 50.4-metre by 29.4-metre wave basin, in which a 1/30 scale model of a natural shoreline comprised of a shallow fringing reef, a sandy shoreline, and several small coastal structures (groynes and breakwaters) was constructed. Wooden dowels and tree branches, scaled to replicate the size distribution of woody debris observed on Pacific Northwest shorelines, were released in the model. Despite some limitations (e.g., model scale effects), the experimental test results provided several valuable insights to factors affecting debris mobility in coastal areas. The results will inform the parameterization of important physical processes in a numerical model being developed to predict the fate and transport of woody debris in coastal waters.
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