Evaluating XBeach performance for extreme offshore-directed sediment transport events on a dissipative beach

ABSTRACT

The performance of the process-based nearshore model XBeach for predicting extreme offshore-directed sediment transport was investigated using field observations at a dissipative beach in Japan. Three extreme erosion events were identified from a record of 6,209 observations of the cross-shore profile change at Hasaki, Japan, from 1987 to 2003. The analysis considered the sensitivity of the wave nonlinearity of short waves that could be tuned using the parameter, f_ua, to the observed bed profile change. The comparisons revealed that for extreme offshore-directed sediment transport events, f_ua = 0.0 is the best fit for predicting these extreme beach profile changes. In the nearshore zone, erosion was underestimated, and the BSS exhibited low values. Peak sediment deposition occurred in the bar-offshore zone with sediments transported from the nearshore zone and was estimated by the model reasonably well. In addition to the three extreme events, 14 other large events were identified, and the trends of beach profile change could be estimated with sufficient tuning of the f_ua parameter. After analyzing the correlation between f_ua and wave and morphology-related parameters, the f_ua value could be correlated to the observed volume change. This suggested that if there were a rough estimate of the expected total volume change, this may help in setting f_ua value.

KEYWORDS:

• Cross-shore sediment transport
• beach profile change
• volume change
• field data

Acknowledgments

We express our thanks to reviewers for their valuable comments and discussion. We could improve by following the reviewer’s suggestions. The authors also would like to thank the Coastal and Estuarine Sediment Dynamics Group, and Marine Information Group of Port and Airport Research Institute and Kashima Port and Airport Construction Office, for allowing the use of beach profile and wave data at the Hazaki Oceanographical Research Station and wave data from the Port of Kashima. This research was funded by JSPS Grants-in-Aid No. 26709034 and No. 15KK0202. The second author was supported by the National Science Foundation through OCE-1756449.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science [15KK0202]; Japan Society for the Promotion of Science [26709034]; the National Science Foundation [OCE-1756449].