Evaluating proxies of subaerial beach volume change across various time scales and morphologies at Onslow Beach, North Carolina, USA

Proxy methods for measuring beach volume change, such as beach-profile surveys and measuring shoreline change are commonly used in place of three-dimensional surveys. These methods are used at all types of beach morphologies and time frames, but it is unclear whether these measurements represent the true volume change. This study assesses the impact of transect placement on volume change measurements and the performance of the shoreline change proxy at varying time frames (0.5--3.5 years) and morphologies (e.g. beach cusps, nourishment). Results indicate that transect placement is important over both short- and longer-time frames at beaches with high-along-beach morphologic variability, high temporal variability in shoreline position, and periodic nourishment. Transect placement does not impact volume change measurements over longer (∼3.5 year) time scales at beaches with rapid and consistent volume change. The shoreline change proxy works best at beaches with low temporal variability in shoreline position and where there are no significant morphologic changes to the backshore (e.g. beach cusp formation/destruction).