The Gulf waters of the US have been identified by the National Oceanic and Atmospheric Administration (NOAA) for open ocean aquaculture with the establishment of potential sites called Aquaculture Opportunity Areas (AOAs). Developing aquaculture at these sites will require a methodical approach to address social license, permitting, business planning, market research and risk analysis. The University of New Hampshire (UNH) is working with the University of Southern Mississippi (USM) and Dauphin Island Sea Laboratory (DISL) to establish an integrated multitrophic aquaculture (IMTA) system at a demonstration site in Alabama, 2.8 km south of the Fort Morgan peninsula to develop aquaculture in the region. The IMTA structure is based on a successful UNH approach called the “AquaFort.” Since the conditions along the Gulf are considerably different than those of nearshore NH, a thorough engineering analysis was required to develop this demonstration site.
The objective of this presentation is to show the high-fidelity modeling approach used to assess the mooring system capacity of the AquaFort subjected to storms along the Gulf Coast. The procedure includes developing extreme value events for waves, currents and winds. Wave and wind conditions for 50- and 10-year storms were develop using long-term datasets using nearby sites from both the U.S. Army Corps of Engineers – Wave Information Study (WIS) and the NOAA – National Data Buoy Center (NDBC). Wave datasets were modeled using the Generalized Extreme Value (GEV) distribution with the Maximum Likelihood Estimation method. Extreme current datasets were obtained by running a 52-year simulation of a circulation model developed at the University of South Alabama. Combinations of 50- and 10-year storm conditions were used as input in a well-established, time-domain model called OrcaFlex.
A high-fidelity model was then created in the OrcaFlex software to include details such as the HDPE structural pipe, flotation billets, handrails, brackets and decking. This application also required containment specifics consisting of copper alloy mesh for shark protection, “Kikko” jump nets, and an internal knotless net to accommodate the size of the red drum to be stocked in the structure. Simulations were performed with input wave period sensitivity. Results were processed to obtain mooring component specifications and to assess anchor holding power considering uplift angles. The mooring equipment was then purchased and delivered to DISL along with a new AquaFort for deployment in Alabama state waters.