Calibration and assessment of process-based numerical models for beach profile evolution in southern California.

Cross-shore profile response to energetic wave events is challenging to predict because the physics are poorly understood and wave and topographic data are often sparse or unknown. Six events with varying duration, wave intensity and beach slopes are used to calibrate and assess two process-based cross-shore models, CShore and XBeach, at two southern California beaches. Model performance is quantitatively evaluated using high resolution spatiotemporal survey observations along with Brier Skill Scores (BSS) and a Beach Elevation Change Error (BECE) metric that evaluates alongshore-averaged upper beach volume predictions. XBeach is tested with default and site-calibrated parameters. Calibration improved skill for all profiles and events, however XBeach skill scores often remained low and in no case correctly predicted the offshore bar formation. Notably, XBeach is sensitive to the beach profile's calibration depth extent. Upper beach calibration produced significantly different skill than when the full profile was considered. CShore was tested using both the 'Atlantic' and 'Pacific' parameters. Both models predict profile change with limited skill. In their present forms, CShore and XBeach are unable to accurately predict beach profile change on these typical southern California beaches, but when calibrated may provide qualitatively useful beach face erosion estimates. • XBeach and CShore are calibrated and evaluated at two southern California beaches. • Model performance is assessed using the Brier Skill Score and a 'Beach Elevation Change' fit measure. • CShore and XBeach did not accurately predict beach profile change in moderate events. • XBeach calibration is sensitive to beach profile depth extent. • Generally, CShore 'Pacific' parameters produced lower skill scores than 'Atlantic'. [ABSTRACT FROM AUTHOR]