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Reinterpreting the Bruun Rule in the context of equilibrium shoreline models

September 7, 2021
Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models. 
Publication Year 2021
Title Reinterpreting the Bruun Rule in the context of equilibrium shoreline models
DOI 10.3390/jmse9090974
Authors Maurizio D'Anna, Deborah Idier, Bruno Castelle, Sean Vitousek, Goneri Le Cozannet
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Marine Science and Engineering
Index ID 70227662
Record Source USGS Publications Warehouse
USGS Organization Pacific Coastal and Marine Science Center