High-frequency observations of berm recovery using a continuous scanning Lidar

The recovery of beaches following the destructive impact of storms is of significant economic, social and environmental value to coastal communities. This study investigates the recovery of a berm following removal by a storm at Narrabeen-Collaroy Beach, Australia using the unique deployment and remote operation of a Lidar mounted on the rooftop of a beachside building. Near-continuous (5Hz) subaerial profile and swash measurements were observed throughout the entire 2.5 month post-storm recovery period. The results provide new insight into the temporal progression of post-storm berm recovery, identifying three consecutive phases of immediate post-storm deposition, intermediate gradual recovery and final rapid recovery with the welding of intertidal sandbars. Significant berm growth was observed during the final phase with rates of subaerial volume deposition three times greater than those during initial phases. Relatively milder nearshore wave conditions as well as flatter intertidal gradients were found to distinguish rapid from more gradual recovery phases. Beachface progradation and berm aggradation during recovery are captured in detail by the high temporal resolution of the fixed Lidar data, providing insight into parameters governing berm recovery on microtidal, wave-dominated sandy coastlines.