Uncertainty analysis related to beach morphology and storm duration for more reliable early warning systems for coastal hazards

Garzon, Juan L.; Plomaritis, T. A.; Ferreira, Oscar

http://hdl.handle.net/10400.1/17583

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Authors

Garzon, Juan L.

Plomaritis, T. A.

Ferreira, Oscar

Abstract(s)

Early warning systems (EWSs) for coastal erosion are highly cost-effective instruments for disaster risk reduction. Among other aspects, an adequate pre-storm beach morphology and the storm characteristic definition are relevant in determining EWSs prediction reliability. Here, XBeach simulations were used to investigate the beach-dune response to different storm events with varying duration and pre-storm morphologies. Severity was defined using wave height return periods (from 5 to 50 years) and duration variability was established by confidence intervals after an adjustment with wave height. Beach morphology variability included different berm morphologies, including erosional and accretional conditions. Three erosion indicators were used: remaining berm width, dune retreat, and eroded volume. Regarding the pre-storm morphology variability: i) pre-storm conditions highly determined the final berm width for the 5 and 10-year events; ii) antecedent morphology affected dune retreat variability mostly for the 50 year events, and; iii) eroded volume depended on the pre-storm conditions, but the percentage of the eroded volume, relative to the initial conditions, was similar regardless of the morphology. Regarding the storm duration effect: i) this variable had a limited impact on the remaining berm width for the 5-year event; ii) storm duration influenced dune retreat mainly for the 50-year event, determining dune breaching occurrence, and; iii) eroded volume response to changes in duration was similar regardless of storm intensity, except for the 50-year event. According to the obtained results, the implementation of reliable EWSs for coastal erosion needs to assess the uncertainties related to initial/forcing conditions, namely pre-storm morphology and storm duration.