AN ABSTRACT OF THE THESIS OF Erica L. Harris for the degree of Master of Science in Oceanography presented on March 11, 2011. Title: Assessing Physical Vulnerability of the Coast in Light of a Changing Climate: An Integrated, Multi-hazard, Multi-timescale Approach Abstract approved: _____________________________________________________________________ Peter Ruggiero Hazards threaten coastal communities and ecosystems over a wide range of spatiotemporal scales. One of the most pressing concerns for coastal property owners, decision makers, and researchers is the uncertain role that a changing climate will have on the intensity and frequency of these hazards. The significant uncertainties associated with both projected rates of global sea level rise (SLR) and the potential for continued trends of increasing wave heights and changes to storm tracks has made the task of incorporating the impacts of climate change into coastal vulnerability assessments challenging. Within this context of this uncertainty, we present a methodology to directly incorporate the impacts of climate change and variability into coastal vulnerability assessments via an integrated multi-scale, multi-hazard approach. Our quasi-probabilistic technique integrates two coastal hazards (dune overtopping and coastal erosion) over a time scales ranging from individual storm events to multidecadal trends influenced by a variety of climate change scenarios. Since both SLR and changes in storminess have the potential to exacerbate the extent of vulnerable stretches along a coast, these two climate controlled factors are integrated into projections of local total water levels (wave runup plus tides) to assess the relative strengths of their influence on flood and erosion hazards. Despite underlying uncertainties associated with future climate conditions, coastal decision makers need to begin planning for a changing climate now. Therefore, we use a suite of recently published semi-empirical global SLR predictions to develop scenarios of future conditions. The potential for continued changes in storminess is accounted for by developing a range of wave climate scenarios based on decadal observations from regional wave buoys. While this approach has been developed for dune backed coastlines in general, discussed here is application of the technique to a 14 kilometer stretch of the dynamic Northern Oregon coast along which significant coastal erosion and flood hazards are currently perceived. By using simple models to predict the possibility of coastal dune overtopping and the extent of coastal erosion from storm events we can quantitatively assess the relative influence of climate change trends based on projections at various future planning horizons. Incorporation of these future hazard probabilities into the development of coastal hazard maps can provide science-based support to allow prioritization of resource allocation to best prepare coastal communities, fragile ecosystems, and jeopardized infrastructure which are likely to experience accelerated vulnerability due to a changing climate. © Copyright by Erica L. Harris March 11, 2011 All Rights Reserved Assessing Physical Vulnerability of the Coast in Light of a Changing Climate: An Integrated, Multi-hazard, Multi-timescale Approach by Erica L. Harris A THESIS submitted to Oregon State University in partial fulfillment of the requirements of the degree of Master of Science Presented March 11, 2011 Commencement June 2011 Master of Science thesis of Erica L. Harris presented on March 11, 2011 APPROVED: __________________________________________________________________ Major Professor, representing Oceanography __________________________________________________________________ Dean of the College of Oceanic and Atmospheric Sciences __________________________________________________________________ Dean of the Graduate School I understand that my thesis will become part of the permanent collection of the Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. __________________________________________________________________ Erica L. Harris, Author ACKNOWLEDGEMENTS First and foremost, I would like to thank my advisor, Peter Ruggiero. Thank you for the opportunity for involvement in this exciting research, serving as a mentor and bringing me to Oregon. I would also like to acknowledge the funding that provided a means for this idea to become a reality, NOAA‘s National Sea Grant College Program under NOAA Grant #NA06OAR4170010. To my committee members, Jonathan Allan and Tuba Ozkan-Haller, thank you for your involvement. Your advice and support throughout the project has been extremely helpful. I extend this thank you to Paul Komar who has graciously provided input for this project since its conception. Completion of graduate school would have been much more difficult without the Matlab assistance and support of my fellow Nearshore All-Stars: Heather Baron, Katy Serafin, Kristen Splinter, Greg Wilson, Meg Palmsten, Jeremy Mull, Joe Long, Greg Guannel, Betsy Seiffert, Pedro Pereira and David Newborn. You guys rock! I also want to express gratitude to the computer mastery of John Stanley, Tom Leach and Bruce Marler. Without your assistance in navigating network drives and setting up Malab licenses, I would have been lost. Additionally, I would like to thank John Stanley for the never ending supply of bike cover seat—because of you, my rides home from the office on rainy winter days were much drier. I would also like to thank my mom for believing in everything I have chosen to do and cheering me on every step of the way. Your unconditional love and compassion is an inspiration. And lastly, a shout out of gratitude goes to Casey for providing just the right amount of motivation and distraction necessary to complete my degree. TABLE OF CONTENTS Page 1.0 Introduction ................................................................................................................... 1 1.1 Approaches for Assessing Coastal Vulnerability ..................................................... 2 1.2 Objectives ................................................................................................................. 6 2.0 Study area...................................................................................................................... 9 2.1. The U.S. Pacific Northwest ..................................................................................... 9 2.2 The Neskowin Littoral Cell .................................................................................... 14 3.0 Methodology ............................................................................................................... 18 3.1. General approach for quantifying coastal hazards ................................................. 18 3.2. Backshore Characterization ................................................................................... 25 3.3 Development of Wave/Tide Time Series ................................................................ 25 3.4 Development of Climate Change Scenarios ........................................................... 32 3.4.1 Sea level rise .................................................................................................... 33 3.4.2 Wave height trends .......................................................................................... 35 3.4.3 Major El Niño frequency ................................................................................. 38 3.5 Development of Synthetic Time Series .................................................................. 39 4.0 Application to the Neskowin littoral cell .................................................................... 42 4.1 Dune Overtopping ................................................................................................... 45 4.2 Coastal Erosion ....................................................................................................... 48 5.0 Index Based Vulnerability Integration ........................................................................ 52 6.0 Discussion ................................................................................................................... 59 6.1 Sources of Uncertainty ............................................................................................ 59 6.1.1 Backshore Characterization ............................................................................. 59 6.1.2 Wave transformation ........................................................................................ 60 6.1.3 Projecting a future climate ............................................................................... 61 6.1.4 Coastal change models ..................................................................................... 62 6.2 The influence of sea level rise vs. tectonic uplift ................................................... 64 TABLE OF CONTENTS (CONTINUED) Page 6.3 Consideration of local factors influencing vulnerability ........................................ 65 6.4 Time scale dependence on sea level rise trends ...................................................... 67 6.5. Additional Means of Assessing Vulnerability ....................................................... 68 7.0 Conclusions ................................................................................................................. 70 8.0 References ..................................................................................................................