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FEMA Partners with Oceanweather and Scripps Institution of Oceanography to Bring Modeling Expertise to CCAMP OPC Study
Justin Vandever, P.E., Coastal Engineer, BakerAECOM
The study process for a coastal flood study along the California Pacific coast starts many hundreds or thousands of miles offshore in the vast Pacific Ocean basin.  Waves that run up on our beaches, causing inundation or erosion, can be generated by stormy conditions as far away as the Gulf of Alaska, New Zealand, or close to home by strong winds blowing over the ocean’s surface. In order to predict coastal flooding and erosion processes at the shoreline, we must first develop an understanding of how waves are generated, travel, and transform as they move across the ocean and into nearshore areas.
As part of the California Coastal Analysis and Mapping Project (CCAMP) Ocean Pacific Coast (OPC) Study, FEMA brought together two key partners, Oceanweather, Inc. (OWI) and Scripps Institution of Oceanography (SIO), to provide deepwater and nearshore wave modeling expertise.   In collaboration with FEMA’s study contractor, BakerAECOM, the study team is producing a 50-year hindcast (1960 through 2009) of wave climatology for the entire California coastline – the most comprehensive dataset of its kind ever created for a west coast flood study.  A hindcast is a historical reconstruction of past meteorological and oceanographic conditions based on observational data and numerical modeling of past conditions.  Oceanweather, Inc. used historical meteorological data from pressure charts, shipboard observations, buoys, and satellite measurements to reconstruct atmospheric conditions throughout the Pacific Ocean basin for the duration of the hindcast period.  Using advanced numerical modeling techniques, the historical wind forcing was applied to a wave generation and propagation model to simulate a 50-year continuous record of deepwater wave conditions offshore of the California coastline.
As waves move from deep water to shallow water, they undergo complex interactions with the seafloor which act to transform the waves and change their characteristics. Wave energy is focused in some areas and defocused in other areas depending on a variety of factors, including wave period and direction, seafloor topography, and coastline exposure.  Scientists and engineers typically use advanced modeling techniques to capture this spatial variability and make wave predictions in areas where direct buoy measurements are unavailable.  Using a numerical model developed by researchers at the SIO Coastal Data Information Program (CDIP), the study team transformed the deepwater wave conditions from OWI’s offshore hindcast to determine the coincident wave conditions at the shoreline. Wave model output is recorded in 10-15m water depths (at the edge of the surf zone) at a spacing of 100-200m alongshore. The high resolution of the wave transformation model output ensures that accurate nearshore wave data are applied to each coastal reach within the study area.  Various wave parameters, such as wave height, period, and direction, are computed and archived with the model hindcast data at each output point for later use in wave run-up computations at the shoreline.
Additional information about OWI and SIO CDIP can be found on their websites: OWI and CDIP.

 Coastal Beat Story Archive

collapse Year : 2012 ‎(7)
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collapse Year : 2013 ‎(19)
<a href=''>FEMA Partners with Oceanweather and Scripps Institution of Oceanography to Bring Modeling Expertise to CCAMP OPC Study</a>
<a href=''>FEMA Region IX Holds Meetings for the California Coastal Analysis and Mapping Project / Open Pacific Coast Study</a>
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<a href=''>Translating Coastal Flood Hazard Modeling Results into Floodplain Mapping</a>
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<a href=''>Join FEMA’s Community Rating System Program Using California’s Statewide Floodplain Management Activities</a>
<a href=''>Coastal Flood Processes Along the California Coast</a>
<a href=''>FEMA’s Annual Risk Awareness Survey: Findings from Previous Surveys and the Focus for the 2013 Survey</a>
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