Jose, F., Kobashi, D. and Stone, G.W., 2007. Spectral Wave Transformation over an Elongated Sand Shoal off South-central Louisiana, U.S.A. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 757 – 761. Gold Coast, Australia, ISSN 0749.0208
Ship Shoal is an elongated sand shoal located along the 10 m isobath in south-central Louisiana adjacent to a rapidly eroding barrier island complex, Isles Dernieres. High quality sand resources from this shoal are considered as a viable source for the long term maintenance of the adjacent barrier islands. Previous wave modelling studies suggest that the shoal acts as a submerged barrier and mitigates storm waves. The present investigation employs a fully spectral finite element model to estimate the wave transformation over the shoal during a cold front generated storm event in April, 2005. MIKE 21, a spectral wave model, was implemented for the eastern Ship Shoal area at a high resolution scale, to estimate wave attenuation over the shoal and to better understand the directional spectrum when the storm–generated waves cross the shoal. The fine resolution coastal model was nested within a regional wave model for the Gulf of Mexico. NCEP re-analysed wind data were used as input and the spatial distribution of bottom sediments were also included in the model to select an appropriate friction factor. It was found that southerly storm waves could lose as much as 22% of their offshore wave height while propagating over the shoal. This level of wave energy reduction also points to the effectiveness of the shoal in shielding the already vulnerable coast against the frequent cold fronts and hurricanes. The model results were validated with time series data collected from in situ measurements on the shoal as well as using data from an observation site CSI 6. The dissipating wave energy over the shoal helps in resuspension and transport of shoal material during storm events.
