Circulation and Sediment Transport at Headlands with Implications for Littoral Cell Boundaries By DOUGLAS ADAM GEORGE B.S. (Humboldt State University, Arcata) 1999 M.S. (Columbia University, New York City) 2001 M.Sc. (Dalhousie University, Halifax) 2003 DISSERTATION Submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Hydrologic Sciences in the OFFICE OF GRADUATE STUDIES of the UNIVERSITY OF CALIFORNIA DAVIS Approved: _____________________________________ John L. Largier, PhD, Chair _____________________________________ Brian P. Gaylord, PhD _____________________________________ Gregory B. Pasternack, PhD Committee in Charge 2016 i Copyright © Douglas Adam George 2016 All rights reserved. Douglas Adam George September 2016 Hydrologic Sciences Circulation and Sediment Transport at Headlands with Implications for Littoral Cell Boundaries Abstract Coastal communities face the highest base sea level elevations in human history as the uncontrolled experiment of anthropogenic-driven climate change continues. Coastal engineering is expected to greatly expand as protection of infrastructure, property, and habitats becomes increasingly necessary. One of the most basic approaches in the protection toolbox is beach nourishment – the practice of placing large volumes of sand on existing beaches to shore up dunes and create a wider buffer from the ocean. The underlying assumption to beach nourishment projects is that they are temporary and will be repeated as the sand washes away over time. The clash between the natural coastal processes of littoral drift and the human efforts to build beaches leads to the framing question of this dissertation – where should sand be or not be placed to maximize the efficacy of a climate change adaptation strategy? The most exemplary coastal engineering projects dovetail with natural features to positively exploit fluid dynamic processes that are self-perpetuating and universal. For example, using a rocky headland as a protective anchor against erosion is prudent to optimize the longevity of a sand placement – yet most research has been conducted on beaches that are somewhat removed from the effects of ii headlands. Further, not all headlands are equal, though, and some may not provide any benefits to a nourishment project. This dissertation focuses on the knowledge gap about how sediment moves around headlands. Historically, studies on the hydrodynamics of headlands have emphasized tide- dominated systems through observations and numerical modeling. This yielded an opportunity to explore circulation and sediment transport around headlands located on wave-dominated coasts. Three studies were undertaken to conduct a deeper investigation on the geomorphic, oceanographic, and sedimentologic influences on sediment flux. The first used a GIS-based classification of headlands to identify morphological features common among 78 California headlands that may or may not perform as littoral cell boundaries. The second executed a field observation study at a large headland in southern California with the goal of understanding sediment pathways and patterns under different forcing conditions. The last study was a numerical modeling effort using Delft-3D and SWAN to identify how variable oceanographic and sedimentologic conditions affect sediment transport around four idealized headlands that were designed based on the first study. Through these three studies, headland size and shape coupled with incident wave angle emerged as the dominant factors influencing sediment pathways and sediment grain size determined the volume of sediment flux. The findings in each study were interpreted in the context of littoral cell boundaries, in particular to assess the “openness” of a headland-defined boundary. Assigning gradations of boundaries instead of the more commonly used “boundary” or “no boundary” monikers became apparent from the results that revealed sediment pathways varied by sediment grain size. The overarching conclusion from this dissertation is that a new set of parameters should be utilized to define littoral cell boundaries at headlands that take into account size, shape, and sediment. The headlands most iii likely to be candidates for absolute boundaries are large, pointed ones for most common beach- sized sand while large, broad-faced ones are barriers for coarser sand but not finer sand; smaller headlands are less likely to be absolute boundaries in general but can be barriers for coarser sand under certain conditions. The discoveries presented herein expand knowledge of headland dynamics as it relates to particle transport and delineation of dynamic littoral cell boundaries, both of which lead to the prospect of improved coastal management decisions in an era of profound coastal change. iv Acknowledgements My dissertation is the product of the support and guidance from a slew of people including my advisor, John Largier, my UCD committee, Greg Pasternack and Brian Gaylord, and my USGS committee, Curt Storlazzi and Patrick Barnard. John was open to me being a part- time student trying to sustain my career and myriad of challenges associated with conducting my research from afar; this product came about from his collegial style with me that respected my background and prompted growth in new areas. Greg also greatly assisted me in navigating the UCD realm and battled on my behalf many times, including unexpectedly providing student funding more than once. Curt and Patrick were stalwarts who encouraged me to grow and keep my eye on the prize. Numerous others provided intelligent conversations, tutoring, and thoughtful discourse during these past four years: Rocko Brown, Justin Vandever, Matt Robart, my sugar mama Phyllis Grifman, members of the Coastal Sediment Management Workgroup, colleagues at the USGS including Li Erikson, Guy Gelfenbaum, Andrew Stevens, and Jon Warrick, and my labmate Kate Hewett. The backing of my friends through this experience was grounding and invaluable and so I thank Liz Pittinos, Joe Toland, Lori Kelly, Amy East, Steve Grimes, Nena Vandebroek, Ken and Laura Krueger, Conor and Joél Flannery, Amy Foxgrover, Paul Melvin, Sean Corcoran, Kathi Koontz, my ETC family, and many others. Covering the geography from Bodega Marine Laboratory to Davis to Santa Cruz was only possible with the generosity of guest rooms and couch space from more than a dozen friends and family, and my trusty set of wheels, Digdoug. I was also fortunate to garner the support of my employers at ESA and AMS who allowed me the space to balance two worlds. I thank my siblings, Amber and Peter, my cousin Danielle, my Aunt Georgette and Uncle Joe, and my nephews, Daniel and Gabriel, for celebrating the highs and enduring the lows with me. Finally, I thank my parents who have stood behind me for more than a decade to help me realize this dream – there’s no doubt in my mind that without their love and encouragement from this earthly place (Mom) and from beyond (Dad), I would not have accomplished this PhD. To understand the heart and mind of a person, look not at what he has already achieved, but at what he aspires to. -Khalil Gibran v Chapter Specific Acknowledgments In addition to the individuals named above, the following provided further assistance that was greatly appreciated for the three studies. Chapter 2 Elena Vandebroek, Dennis Hall (NOAA), and Joshua Novac and Erin Musgrave (Dewberry) provided geospatial technical assistance and data and Li Erikson (USGS) provided wave data. Discussions regarding geomorphology with Rocko Brown and cluster analysis with Christie Hegermiller helped guide this research. The published manuscript from Chapter 2, which was co-authored with John, Curt, and Patrick, was improved upon by review from Bruce Jaffe (USGS), Edward Thornton (NPS), and an anonymous review. The methodological appendix, published under a co-authorship with Elena, benefitted from review by Clif Davenport (CGS), John Dingler (USACE), and Nancy Ferris (BAAMA). The Hydrologic Sciences Graduate Group at the University of California Davis and the US Geological Survey’s Coastal and Marine Geology program supported this work. Chapter 3 The field observational component of this dissertation was completed in Malibu with extensive assistance from the following individuals: Matt Robart, David Dann, and Brian Gaylord (all BML), Tom Ford (The Bay Foundation), and Dan Hoover, Tim Elfers, Andrew Stevens, and Jackson Curry (all USGS). Instruments came from John, Brian, Curt, and Patrick. Jon Warrick (USGS) provided guidance for sediment photogrammetry. This work was produced with support from the USC Sea Grant Program, National Oceanic and Atmospheric vi Administration, U.S. Department of Commerce, under grant number NA14OAR4170089, and the USGS Coastal and Marine Geology program. Unpublished work off Bodega Head utilized the assistance of Matt Robart and David Dann (both BML), and Sam Johnson (USGS), with funding from the PADI Foundation and the UC Natural Reserve System. Chapter 4 The monumental modeling task could not have been attempted nor completed without the deep involvement of Edwin Elias, Andrew Stevens, Li Erikson, and Andrea O’Neill (all USGS). Patrick provided a much-needed modern computer that accelerated the process many times over. The USC Sea Grant Program, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, financially supported the modeling under grant number NA14OAR4170089, with substantial computer and software support from the USGS Coastal