The Role of Climate Change and Variability in the Erosion of the U. S. West Coast: Research, Management Tools, and Outreach

Earth’s variable and changing climate exerts a strong control on beach and property erosion along the U.S. West Coast. Occurrences of El Niños are a major factor and the impacts associated with these events are increasing when combined with the progressive increases in storm intensities and generated wave heights that are likely a response to global warming. For example, the massive coastal erosion and flooding that impacted development along the entire West Coast during the 1998 winter (losses in California alone were estimated to be $1.1 billion) was the result of an El Niño that was accompanied by a series of extreme storms waves. This led to the discovery that winter storm waves have been increasing in heights since wave-buoys were installed approximately four decades ago.

To support decision makers in their efforts to manage coastal resources in a changing world, the
goals of this proposed study include improving our understanding of climate controls on coastal
hazards (e.g. erosion and flooding), enhancing coastal-hazard models that incorporate climate
controls, assessing societal vulnerability to these hazards, and developing resources and tools to
support coastal resource, land-use, and emergency managers. Research and enhanced models
include projected physical responses and socioeconomic indicators and will be applied to select
west coast coastal communities to assess and quantify coastal vulnerability associated with climate change and variability.

To improve our understanding of climate controls on coastal hazards, we propose to:

• Document the climate controls on wave conditions, specifically the extension of deep-water wave climates to formulate near-shore processes, for the entire West Coast, with particular focus on the enhanced extremes that represent the greatest future hazards;
• Investigate the climate factors important to the magnitude and spatial variability of West
  Coast storm surges that also lead to erosion;
• Examine the processes that account for El Niño enhanced water levels, how they vary with latitude, and account for their roles in the resulting coastal impacts; and
• Document the large-scale shifts in beach sand volumes, which have been significant during El Niños and analyze those shifts in terms of the climate controls on wave heights and directions.

To enhance coastal-hazard models, we propose to:

• Incorporate climate controls into a series of integrated models we have developed to assess the potential for beach and property erosion, including a model that predicts total water level elevations, a second model that projects the maximum potential extent of foredune erosion during major storms, and a third model that assesses sea-cliff erosional retreat;
• Document dune erosion in major storms through field measurements to improve modeling of storm-induced erosion;
• Develop a new process-based model that better accounts for the time history of dune
  erosion and its lag behind oceanic processes.

To assess societal vulnerability to coastal hazards and related climate-change controls, we propose to:

• Document the physical and social impacts of significant historical erosion events as a way to couch natural-science information into a societal context and ensure practitioner interest;
• Determine the needs and decision-making context of coastal land-use and emergency
  managers for issues related to coastal flooding and erosion; and
• Combine model predictions of physical coastal change and flooding under various climate change scenarios with current and projected socioeconomic indices (e.g. land use, land cover, populations, and economic factors) in selected communities.

To support coastal resource, land-use, and emergency managers, we will:

• Establish a stakeholders working group that will provide input and feedback throughout the process to ensure end products meet their needs;
• Partner with the NOAA Coastal Service Center (see letter of support), to modify the Coastal Inundation Visualization (CIV) tool (http://www.csc.noaa.gov/cspPNW/) to include a variety of parameters such as historical, real-time, and projections of extreme storm impacts, as well as integration with current and projected socioeconomic indices to quantify coastal vulnerability;
• Provide custom training to stakeholders on how to use the products of the research;
• Develop web-based educational modules that summarize how other coastal scientists and engineers can apply the enhanced models in coastal-hazard assessments; and
• Develop a webpage that includes educational material geared for the general public and
  technical information (ex. data and models) for other coastal scientists and engineers.

To accomplish the above research, application, and educational goals, we propose a multi-scale
approach. Our research documenting climate controls on wave conditions and the resulting largescale shifts in beach sand volumes will focus on datasets that encapsulate the entire coast (e.g. wave-buoy and lidar data), as these processes operate on a regional scale. We intend to use case studies that focus on two jurisdictions to improve existing models, assess societal vulnerability, and modify on-line mapping tools. The two case studies will focus on county-level decision-making and will likely center on Tillamook County, Oregon, and Pacific County, Washington. Having two case studies in different States allows us to investigate the influence of different planning and regulatory context on the use of the enhanced models.

Understanding how changes in the Earth’s climate attenuate or amplify coastal processes is critical if resource, land-use and emergency managers are to understand the potential for coastal hazards and societal vulnerability to these threats. Accomplishing the above research goals will greatly improve our ability to project the expected future impacts of Earth’s changing climate on the erosion of the U.S. West Coast beaches and shorefront properties and support local and State practitioners in their efforts to manage resources in this dynamic zone.