Will the sand come back? Observations and characteristics of beach recovery

An understanding of how a beach will recover following storm erosion is of significant value for beach management. Knowledge of timescales and key parameters governing the recovery of beaches, acting as protective sand buffers, would better inform both decision-makers in planning and design, as well as, public perceptions and expectations. While much emphasis has been placed on accurately predicting erosion for specific storm events, this is temporally limited. In modelling the impacts of storm clusters and longer-term (years to multi-decadal) beach variability and evolution, recovery rates are often neglected or simplistically fitted with little understanding of forcing parameters. Going forward, an improved understanding of how and when beaches recover is a vital component to risk assessment associated with storm clustering and future climate change scenarios. This study uses a decade of daily beach width observations obtained from an ARGUS coastal image station at Narrabeen-Collaroy Beach in south-east Australia, to distinguish and quantify beach width recovery following substantial erosion (greater than 20 m in beach width) associated with single storms and clusters of several storm events. Timescales and rates of beach width recovery are calculated from ten identified recovery periods, defined by the return of beach width to a pre-storm(s) value. A relatively consistent net rate of beach width recovery at this site of 0.05 to 0.15 m/day is observed, spanning typical durations of several months to a year. At higher temporal resolutions (days to weeks) beach width recovery rates are found to be variable and complex. This study demonstrates the use of long-term field data measurements to better inform a quantitative understanding of beach recovery that it is often lacking in coastal risk assessment