USGS – Modeling Shoreline Change in Southern California

Using a newly-developed computer model called CoSMoS-COAST (Coastal Storm Modeling System – Coastal One-line Assimilated Simulation Tool) scientists predict that with limited human intervention, 31 to 67 percent of Southern California beaches may become completely eroded by the year 2100.

“Losing the protecting swath of beach sand between us and the pounding surf exposes critical infrastructure, businesses and homes to damage. Beaches are natural resources, and it is likely that human management efforts must increase in order to preserve them,” said lead author of the study, Sean Vitousek.

Vitousek continued by saying that although a majority (72 percent) of beaches in Southern California show historical trends of accretion or getting larger (due to large artificial beach nourishments since the 1930s), future predictions indicate that nearly all of the beaches will experience erosion due to accelerated sea-level rise.

“This study indicates that we will have to perform massive and costly interventions to preserve these beaches in the future under the erosive pressures of anticipated sea level rise, or risk losing many of the economic and protective benefits beaches provide,” said USGS geologist and coauthor, Patrick Barnard.

Important for coastal hazard assessment and management planning, CoSMoS–COAST is a numerical model used to predict shoreline-change due to both sea level rise and changing storm patterns driven by climate change.

The model takes into consideration sand transport both along the beach (due to longshore currents) and across the beach (cross-shore transport) by waves and sea-level rise.

Although Southern California beaches are a complex mixture of dunes, bluffs, cliffs, estuaries, river mouths, and urban infrastructure, the model is applicable to virtually any coastal setting.

Vitousek, who was a post-doctoral fellow at the U.S. Geological Survey when he conducted this study, is now a professor in the Department of Civil & Materials Engineering at the University of Illinois at Chicago.