Cost-effective coastal flood adaptation requires a realistic valuation of losses, costs, and benefits considering the uncertainty of future flood projections and limited resources for adaptation. This study presents an approach to quantify the flood protection benefits of beaches, accounting for the dynamic interaction of storm erosion, long-term shoreline evolution, and flooding. Applied in Narrabeen-Collaroy (Australia), the method considers uncertainty in socioeconomic pathways, sea-level rise projections, and beach conditions. Results show that by 2100, neglecting erosion underestimates flood damage by a factor of 2, while maintaining current beach width avoids 785 million AUD in flood damage. By 2050, flood protection and recreational benefits of maintaining the current shoreline could exceed nourishment costs by a factor of 150. These findings highlight the value of beaches for adaptation and can inform financial instruments for restoration.

Alexandra Toimil, Iñigo J. Losada, Moisés Álvarez-Cuesta, Gonéri Le Cozannet