CEE Ph.D. Defense Announcement: Beach Dynamics and Implications for Flood Risk in Southern California

Abstract: Many Southern California beaches are eroding due to a combination of reduced sediment supplies, rising sea levels and wave energy along the coast. Beach loss threatens the economy and cultural identity of Southern California and also contributes to increased flood risks from combinations of high tides and waves. This dissertation presents an innovative computational method to resolve compound coastal flood risks with fine-resolution at the regional scale, examines trends in beach loss and the resulting implications for coastal flood risk, and explores the mechanisms responsible for hot spots of beach erosion and widening. We find that future wave-driven flooding is highly localized in Los Angeles and Orange County, and that Newport Beach is especially vulnerable due to a combination of low topography and narrowing beach widths. On the other hand, beach width has been increasing at Huntington Beach over recent decades, which will help to mitigate future flood risks. Trends in beach width are shown to result from changes in the net sediment movement along the coast caused by wave action, which is highly variable in accordance with wave diffraction and refraction within the Southern California Bight.