HR: 0800h
AN: OS21B-1235    [Abstracts]
TI: Physical Measurements of Sea Bed Roughness
AU: * Nunes, V B
EM: vasco@hawaii.edu
AF: Dept. Ocean Engineering, SOEST, Univeristy of Hawaii, 2540 Dole Street, Holmes Hall 402, Honolulu, HI 96822 United States
AU: Pawlak, G
EM: pawlak@hawaii.edu
AF: Dept. Ocean Engineering, SOEST, Univeristy of Hawaii, 2540 Dole Street, Holmes Hall 402, Honolulu, HI 96822 United States
AB: Physical measurements of sea bed roughness were obtained using a boat-mounted acoustic altimetry system combined with diver-based observations with the goal of resolving scales between 10 and 100cm. The surveyed area extends from the wave breaking zone to a depth of 20 m and is characterized by a highly inhomogeneous sea bed. Theory suggests that these roughness scales play an important role in wave energy dissipation, despite the lack of established parameterizations for these high roughness regimes. This study attempts to address this issue by investigating methods for quantifying roughness and examining the relationships between physical and hydrodynamic roughness. Results show a significant variation of roughness over the study area indicating limitations in defining a single scale for the shallow water region. Various statistical estimators are examined as potential candidates for roughness parameterization schemes, including rms, standard deviation and consecutive angle difference in order to characterize bed morphologies. Wave number spectral analysis is used to highlight the dominant roughness scales. The analysis is directed towards merging the various roughness parameters with wave field observations and numerical wave model output, to produce a roughness map that establishes a link between the physical roughness measurements and hydrodynamic wave friction at the study area.
DE: 4546 Nearshore processes
DE: 4594 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting