Defining a single set of calibration parameters and prestorm bathymetry in the modeling of volumetric changes on the southern Baltic Sea dune coast

• Published in: Oceanologia 2022-01, Vol.64 (1), p.160-175
• Main Authors: Bugajny, Natalia, Furmańczyk, Kazimierz
• Format: Article
• Language: English
• Subjects: Coastal erosion; Model calibration; Volume errors; XBeach
• ISSN: 0078-3234
• DOI: 10.1016/j.oceano.2021.10.004

•The coastal morphology for model calibration process should be recorded as soon as possible before and after the storm event.•Default XBeach parameters are not recommended for modeling volume changes on the southern Baltic dune coast.•An average set of calibration parameters is a reliable alternative to get optimum study area parameters.•Spatial proximity was found to be a not good approach to transfer calibrated parameters at complex coastal systems.•The shallow prestorm bathymetry was found to have evidence influence on modeling volume changes of the sandy coast. The studies described herein aimed to estimate the accuracy of determination of the volumetric changes on the dune coast of the southern Baltic Sea through the application of the XBeach numerical model, which is crucial for coastal engineering. In the first phase of the study, the profile (1D) mode of the model was adapted to 19 cross-shore profiles located along the Dziwnów Spit. The model was calibrated with a storm event in 2009 that caused significant changes to dunes and beaches. Cross-shore profiles were measured approximately one and a half months before and after the storm. An evaluation of model performance was made based on the Brier skill score (BSS), the visual match of the profile shape (VMS), the absolute volumetric change error (m3/m) and the relative volumetric change error (%). In this study, parameters related to the asymmetry transport (facua) and the dune erosion algorithm (wetslp) were taken into account. The best results for model calibration on all 19 cross-shore profiles were obtained with facua values ranging from 0.16 to 0.40 and wetslp values from 0.35 to 0.60. The calibration of individual profiles yielded good results, with an average absolute error of approximately 4 m3/m and an average relative error of ca. 20%. The poorest results were collected for the profiles situated near coastal engineering structures, where the average absolute error was 10 m3/m and the relative error was 60%. The possibility of accepting one set of parameter values for all the profiles at once was also investigated. These studies revealed that the application of one set of facua and wetslp values for all profiles simultaneously resulted in a relative volumetric change error of ca. 25% on average, with the maximum of about 40%. Due to the difficulty of collecting data just before and after the storm event, complex studies using all available bathymetric data were performed. Using a joint da