This research team will create a computer model to imitate how floating cage oyster farms respond to wind, waves, water level and current during tropical storms and hurricanes. The model will consider mooring systems, farm layout, cage location (floating or sunken during storms) and other factors to analyze farm resistance to severe conditions. Scientists will use their model to run different scenarios and study the results to make recommendations to minimize economic losses on farms and improve design specifications, such as line spacing, orientation, anchoring systems, and sinking and refloating cages.

Abstract

Oyster farmers in Mobile Bay and Mississippi Sound lack reliable information on the safety and performance of their infrastructure during extreme weather conditions. Current knowledge is based on anecdotal evidence, which is insufficient for making informed decisions. This research project addresses this gap by utilizing quantitative engineering technologies tailored to the region's conditions. It will bridge this critical knowledge gap by conducting a comprehensive study to enhance the resilience of floating cage oyster farms in the Mobile Bay-Mississippi Sound region. 

The research objectives revolve around the development and implementation of an assessment system specifically tailored for oyster farm infrastructure. Through the creation of a sophisticated three-dimensional fluid-structure-mooring model, validated via laboratory and field experiments, the proposed study will enable accurate simulation of fluid-structure interactions and facilitate the evaluation of realistic farms' resistance to extreme conditions. Furthermore, extensive analysis of long-term environmental data, encompassing factors, such as winds, storm surges, waves and currents, will be undertaken to estimate the precise loading experienced by oyster farms. Extreme analysis techniques will be employed to determine the environmental conditions at various return periods. 

The proposed study includes scenario studies to evaluate the effectiveness of storm preparedness measures, such as sinking cages to the seabed during storms. Sensitivity analyses will be conducted to assess the impact of material degradation, farm layout, orientation and seabed friction on farm survival. These investigations will provide valuable insights into the optimization of farm designs and maintenance practices. The project also involves engaging end-users, particularly oyster farmers, throughout the research process. Farmers will actively participate by providing material supplies, sharing farm layouts and designs, and receiving maintenance recommendations. The research outcomes will directly inform farmers about the safety of their infrastructure and provide practical approaches to enhance resilience.

The findings will contribute to the development of guidelines and recommendations. Moreover, this research directly aligns with the priorities of sustainable fisheries and aquaculture, addressing the need for resilient oyster farm infrastructure. By reducing risks and minimizing economic losses, this study aims to support the long-term viability and sustainability of floating cage oyster farming systems.

Objectives

1. To develop a comprehensive assessment system to evaluate the integrity of floating cage farms.
2. To assess the resilience of floating cage farms to tropical storms and hurricanes.
3. To evaluate the effectiveness of existing tropical storm preparedness in maintaining the integrity of infrastructure during severe weather events.
4. To investigate potential strategies for enhancing the safety and resilience of infrastructure during tropical storms and hurricanes.

Methodology

The project will firstly develop a three-dimensional fluid-structure-mooring model to simulate floating cage oyster farms. This model will enable a comprehensive understanding of the interactions between the fluid dynamics, structural components, and mooring systems of the farms. To validate and calibrate the model, a series of laboratory and field experiments will be conducted. These experiments will provide essential data to ensure the accuracy and reliability of the model's predictions. After validation, the model will be applied to assess the resistance of realistic floating cage farms to extreme environmental conditions of wind, water level, wave and current through extreme analysis. Based on scenario studies, the resilience and integrity of the farms can be evaluated. This analysis will help identify potential vulnerabilities and provide insights into the farms' ability to withstand and adapt to extreme conditions.

Rationale

Off-bottom oyster aquaculture brings economic and social benefits to Alabama and other Gulf coast states. However, the vulnerability of this technique to storms and hurricanes remains a significant concern. The extreme conditions associated with these events can result in failures in mooring systems and significant losses. Recovering from such events poses financial challenges. Oyster farmers in Mobile Bay and Mississippi Sound lack reliable information on the safety and performance of their infrastructure during extreme weather conditions.

There is a significant research gap in comprehensively evaluating the durability and safety of off-bottom floating cage infrastructure under extreme conditions. Factors contributing to mooring failure have not been extensively studied, and the effectiveness of suggested preparations for floating cage oyster farms has not been assessed. The dynamics of floating oyster farms pose challenges in estimating environmental loads and assessing mooring system performance. Impact of material degradation on infrastructure resilience also remains unclear. 

This proposed project addresses these research gaps through comprehensive studies. It is proposed to develop physical models to estimate environmental loads, establish a database of mooring line properties, analyze extreme environmental conditions, and assess the integrity of realistic farms. Valuable insights from this project are directly applicable to the local industry and will inform future development and resilience strategies.