In the Pacific Northwest, dunes are prolific along many sections of the coast. In the early 1900s invasive beach grasses were planted on the dunes to stabilize the sand, creating shore parallel vegetated hills of sand known as foredunes that protect against flooding and erosion. However, some homeowners prefer to grade the dunes for ocean views, potentially limiting their capacity for protection against coastal flooding. We are working to quantify how coastal dune management practices impact dune morphology in order to assess how various management practices may impact the protective capacity of the coastal dunes.

Additionally, the Pacific Northwest is at risk of experiencing a large earthquake and subsequent tsunami caused by a rupture along the Cascadia Subduction Zone. While earthquake and tsunami impacts have been well-studied in the Pacific Northwest, to date most tsunami inundation modeling has not incorporated sediment transport or morphologic change. Because dunes are a large source of sand and are dynamic features, modeling tsunami impacts on Oregon’s dune-backed beaches will help us better understand the morphologic change caused by a tsunami. Additionally, we will investigate the influence of various types of dunes (e.g., tall and vegetated, wide and vegetated, low and unvegetated) on tsunami impacts, to gain a better understanding of how they may (or may not) protect homes and infrastructure from tsunami inundation. Dunes on the Oregon coast have historically been modified to maintain desired ecosystem services such as views of the ocean, so understanding how modified dunes respond to tsunamis has important management implications. We utilize hydrodynamic models with sediment transport capabilities (e.g., FUNWAVE-TVD) to model the tsunami inundation and tsunami-induced morphological change on Oregon’s dune-backed beaches.

Cover of the Oregon Coastal Dune guidebook created as a collaborative document between OSU, DLCD, and OPRD. Photo credit: Carly Ringer.