Observing Multi-Scale Ocean Dynamics off of Rough Rocky Coastlines: Wave Dissipation Observing System
Abstract
Wilsons objectives are to use field observations to study the physics of and validate numerical models of coastal ocean (shoreline to 30 m depth) dynamical processes important to Navy operations. In particular, this proposal focuses on surface gravity wave dissi pation on rocky coastlines. Although 75% of the world coastlines are rocky, limiting Naval Special Forces accessibility, relatively little is known about wave and circulation dynamics in such environments. In contrast to well-studied sandy coastlines, rocky coast lines have complex three-dimensional geometries at scales of centimeters to 100s meters, and often sharp depth gradients. The multi- scale bottom variability (or roughness) has strong effects on wave processes such as scattering, reflection, nonlinear energy transf ers, and important to this proposal dissipation, all of which are dramatically different than on sandy beaches. Rocky shoreline wave dissipation will also strongly affect water-column turbulence and wave-driven currents (rip currents, undertow) feeding back t o the wave field. The accuracy of existing wave models developed for low sloped beaches in predicting rocky shoreline onshore wave p ropagation is unknown, nor is it known what new physics need to be included to make accurate predictions. It is certain, however, th at both bottom drag and wave breaking are first-order processes on rocky shores. This proposal aims to address those specific proces ses in new field experiments for validating theory and models. This is one of a set of three DURIP proposals associated with a submi ssion to the MURI Program, ONR Topic 3: Littoral ocean dynamics off rocky coasts and shorelines by PI team MacMahan/Feddersen/Rosman /Wilson/Kirby/Kumar. It will include a comprehensive set of field experiments and associated modeling of wave, circulation, and turb ulence processes on different rocky shoreline types in the Monterey, California, region, representative of rocky shores worldwide. I n support of this effort, this proposal aims to create a system for observing wave dissipation due to (a) bottom drag and (b) wave b reaking. Specifically, the system consists of: a) Elements of an Obstacle-scale Array (collaborative with Rosman DURIP), for measuri ng the drag and frictional dissipation associated with large rocky roughness elements, for which dominant forces and length scales i nvolved are not presently well understood. Equipment is requested to measure the wave bottom boundary layer at high resolution, to m easure form drag, and to obtain detailed seabed roughness and bottom-type information. b) Equipment for remote sensing of wave break ing dissipation. This includes a shore-based video camera system, and a UAS lidar/video quadcopter (US-made and recently waiver-appr oved for NDAA), to be used with newly-developed remote sensing techniques for measuring (i) wave breaking dissipation and (ii) spati ally-variable nearshore surface currents.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 07, 2021
- Source ID
- N000142112711
Entities
People
- G. Wilson
Organizations
- Office of Naval Research
- Oregon State University
- United States Navy