Comparison of sonographs taken before and after Hurricane Diana, Onslow Bay, North Carolina

High-resolution, side-scan sonar data collected from the middle continental shelf of Onslow Bay, North Carolina, before and after an intense storm (Hurricane Diana, September 11-13, 1984) were used to investigate the impact on this shelf surface. Wave hindcasting predicts that significant wave heights and periods were 6 m and 10 s during the storm9s passage, and horizontal water velocity at the sea floor was 125 cm/s. Comparison of prestorm and poststorm sonographs revealed no measurable sea-floor changes. Distinct spatial patterns representing textural variations between Miocene muddy sand and coarse Holocene clean sand, as well as extensive areas of loose rock debris, appeared similar. The storm-dominated nature of this shelf surface results primarily from its sediment-starved existence and the equilibrium that has been reached with the region9s ambient, high-energy setting.