Hope Zones: Engineering a Seaweed Farm for Nazaré’s Atlantic Conditions
Kelson Marine combined ocean data, wave modeling, and dynamic structural analysis to define design requirements for Hope Zones Foundation’s proposed seaweed farm off Nazaré, Portugal.
Hope Zones Foundation has a vision to see ocean regeneration deployed at scale to every surf-blessed coastline in the world. They see seaweed farming in coastal areas around the world as essential, useful, and practical to bring economic innovation to potential and existing Maritime Protected Areas (MPAs). asked Kelson Marine to evaluate a seaweed cultivation system in the coastal waters off Nazaré, Portugal. The proposed farm was located within a uniquely constrained artificial reef area and exposed to extreme Atlantic waves, making cost-effective farm design especially challenging.
Our work connected the ocean conditions at the site to the structural requirements of the farm. We estimated design conditions, simulated how a representative longline would respond, and provided requirements for its lines, floats, and anchors.
The ocean has given me a lifetime of lessons, joy, and challenges. Through this seaweed farm, we can give back – restoring the coast, supporting our community, and protecting our oceans for future generations.
Understanding conditions at the farm
We used available ocean observations and numerical model data to estimate the waves, currents, wind, and water levels that the system would need to withstand. Offshore measurements alone do not describe conditions at a coastal farm. As waves approach shore, the seabed changes their height and direction.
Kelson ran a coastal wave model to account for these effects and translate offshore wave conditions to the project site. This gave the structural analysis a basis tied to the farm’s location and surrounding bathymetry.
Simulating a flexible cultivation system
We built a dynamic numerical model of a representative longline and evaluated its response under 50-year design storm conditions. The analysis considered forcing along the line, across it, and at an oblique angle, at both high and low water levels. It included combinations dominated by waves and combinations dominated by currents.
The simulations allowed us to estimate component loads while accounting for the system’s motion and flexibility.
The Nazaré project area and the ocean data sources used to characterize design conditions. The regional map shows the wave-model domain; the local map shows the project area near the existing artificial reef.
Turning analysis into design requirements
Kelson used the results to specify required capacities for ropes and chains, size the floats, and evaluate anchor holding requirements. We also provided guidance on mooring geometry and line tension, including how to accommodate differences in anchor spacing.
The completed work gave Hope Zones a site-specific farm design engineered for the world-famous wave conditions of Nazaré.
