Southern California coastal response to CMIP5 projected 21st century wave conditions

Recent projections of 21^st century Eastern North Pacific deep-water wave conditions under climate change scenarios predict slightly decreased significant wave heights, increased peak wave periods, and more southerly wave directions offshore of Southern California relative to historical conditions. Combined dynamical and statistical efforts were employed to project wave climate-driven changes in local erosion and accretion patterns along the Southern California coast based on these deep-water wave projections. The numerical wave model SWAN was forced with USACE WIS hindcast bulk wave parameters and reanalysis near-surface winds to generate nearshore wave conditions at the 5 m contour from 1980-2010. A nontraditional lookup table was created to establish the functional relationship between deep-water wave conditions defined by the ERA-Interim wave reanalysis and nearshore wave conditions simulated with SWAN. Historical and future deep-water wave time series were translated to the nearshore via the lookup table. Refraction across the continental shelf reduces the difference between projected and historical nearshore wave angles. Never the less, changes in gradients in longshore transport, resulting from long-term changes in wave angle, create new hot spots for erosion and accretion. This work identifies potentially vulnerable areas on which to focus protection and mitigation efforts and provides an approach for assessing how the future evolution of the wave climate due to climate change may affect coastal processes and hazards.