A COASTAL OBSERVING SYSTEM TO MONITOR COASTAL PROCESSES DURING EXTREME EVENTS IN A HETEROGENOUS SEDIMENTARY ENVIRONMENT, NORTHERN GULF OF MEXICO

The morphological impacts and importance of Tropical Cyclones on the northern Gulf of Mexico coast have been well documented in the past. Considerably less, however, is known regarding the evolution of the wave and current field as storm systems move shoreward to landfall. Beginning in 2000, a geographically distributed coastal ocean observing system (WAVCIS) was designed and partially implemented off the Louisiana coast consisting of an array of metocean sensors reporting in near real time. The system's architecture was designed to function in severe storm/hurricane conditions. The distribution of sensors was carefully undertaken to capture the hydrodynamic signature of high energy events in markedly different geological environments on the continental shelf; west Louisiana is characterized by an inner shelf composed of fine-grained sediment whereas east of the Atchafalaya River, bottom sediments tend to be coarser. When compared, both environments provide an ideal laboratory for studying the effects of cohesive sediment properties on wave propagation, bottom interaction and dissipation. Here we describe the system's architecture and present a unique data set capturing three Tropical Cyclones (TS Isadore, H. Lili and TS Bill). The former two events impacted the Louisiana coast in September/October, 2002 and Bill made landfall in the same general area in July 2003. Interpretation of the spectral evolution of storm waves is presented for wave propagation into shallow water and protected bays. Skill assessment of an advanced numerical wave model (SWAN) is also undertaken after running the model in non-stationary modes. Findings from this work have important implications for better understanding wave behavior during extreme events, bottom interaction in cohesive sedimentary inner shelf environments and enhancing numerical wave capabilities.