A Bayesian network approach to modelling rip-current drownings and shore-break wave injuries
Open Access
- 9 July 2021
- journal article
- research article
- Published by Copernicus GmbH in Natural Hazards and Earth System Sciences
- Vol. 21 (7), 2075-2091
- https://doi.org/10.5194/nhess-21-2075-2021
Abstract
A Bayesian network (BN) approach is used to model and predict shore-break-related injuries and rip-current drowning incidents based on detailed environmental conditions (wave, tide, weather, beach morphology) on the high-energy Gironde coast, southwest France. Six years (2011–2017) of boreal summer (15 June–15 September) surf zone injuries (SZIs) were analysed, comprising 442 (fatal and non-fatal) drownings caused by rip currents and 715 injuries caused by shore-break waves. Environmental conditions at the time of the SZIs were used to train two separate Bayesian networks (BNs), one for rip-current drownings and the other one for shore-break wave injuries. Each BN included two so-called “hidden” exposure and hazard variables, which are not observed yet interact with several of the observed (environmental) variables, which in turn limit the number of BN edges. Both BNs were tested for varying complexity using K-fold cross-validation based on multiple performance metrics. Results show a poor to fair predictive ability of the models according to the different metrics. Shore-break-related injuries appear more predictable than rip-current drowning incidents using the selected predictors within a BN, as the shore-break BN systematically performed better than the rip-current BN. Sensitivity and scenario analyses were performed to address the influence of environmental data variables and their interactions on exposure, hazard and resulting life risk. Most of our findings are in line with earlier SZI and physical hazard-based work; that is, more SZIs are observed for warm sunny days with light winds; long-period waves, with specifically more shore-break-related injuries at high tide and for steep beach profiles; and more rip-current drownings near low tide with near-shore-normal wave incidence and strongly alongshore non-uniform surf zone morphology. The BNs also provided fresh insight, showing that rip-current drowning risk is approximately equally distributed between exposure (variance reduction Vr=14.4 %) and hazard (Vr=17.4 %), while exposure of water user to shore-break waves is much more important (Vr=23.5 %) than the hazard (Vr=10.9 %). Large surf is found to decrease beachgoer exposure to shore-break hazard, while this is not observed for rip currents. Rapid change in tide elevation during days with large tidal range was also found to result in more drowning incidents. We advocate that such BNs, providing a better understanding of hazard, exposure and life risk, can be developed to improve public safety awareness campaigns, in parallel with the development of more skilful risk predictors to anticipate high-life-risk days.Funding Information
- Agence Nationale de la Recherche (ANR-17-CE01-0014)
This publication has 43 references indexed in Scilit:
- Surf zone hazards and injuries on beaches in SW FranceNatural Hazards, 2018
- Rip current types, circulation and hazardEarth-Science Reviews, 2016
- Impact of the winter 2013–2014 series of severe Western Europe storms on a double-barred sandy coast: Beach and dune erosion and megacusp embaymentsGeomorphology, 2015
- A suitable metocean hindcast database for the design of Marine energy convertersInternational Journal of Marine Energy, 2013
- Rip current related drowning deaths and rescues in Australia 2004–2011Natural Hazards and Earth System Sciences, 2013
- Rip Current Prediction: Development, Validation, and Evaluation of an Operational ToolJournal of Coastal Research, 2012
- Modeling rip current circulations and vorticity in a high‐energy mesotidal‐macrotidal environmentJournal of Geophysical Research: Oceans, 2011
- Temporal observations of rip current circulation on a macro-tidal beachContinental Shelf Research, 2010
- SURF SIMILARITYCoastal Engineering Proceedings, 1974
- LII. An essay towards solving a problem in the doctrine of chances. By the late Rev. Mr. Bayes, F. R. S. communicated by Mr. Price, in a letter to John Canton, A. M. F. R. SPhilosophical Transactions of the Royal Society of London, 1763