To develop a complete understanding of our research, we rely on understanding the integrated relationships at all scales: from microorganisms to ecological cycles of gas and nutrient exchange.

This surface wave-resolving numerical model is simulating the performance of a network of frictional mass units in a channeled wave-tank environment. This model was one of our earliest methods for physical simulation; subsequent physical prototyping and wave tank experiments have allowed us to compare the model behavior with a variety of laboratory-observed conditions and tune its accuracy. In other words, the physical dynamics shown here are true to the way an eight-row network of actual marine biomass units would affect regular waves of 2-foot height and 6-foot wavelength—the wave formation would diffract as shown, and overall wave energy would be reduced by over 70%. By adjusting the input parameters of the simulation, such as wavelength and network configuration, the model is able to calculate corresponding conditions of the resultant wave behavior as it reacts to the different configurations. This allows for the optimization of the size and configuration of an Emerald Tutu project based on the environmental conditions of a particular site

In creating this model and observing how the simulated waves interact with a simulated unit network, we were able to generalize the reactive properties of the marsh mat network that produce the wave dampening effect. Through validation from the Wave Tank Lab Tests, we confirmed that with enough rows, an Emerald Tutu network can progressively dampen any wave. We also found that the unit spacing affects damping properties, with tighter networks more effective at damping incoming waves. Diversifying the size of the mats also improved damping efficacy, but was not as impactful as the network spacing. Try the interactive Data Viewer GUI to see how these factors affect performance in varying wave conditions.

To create a mathematical representation of the floating unit network in this simulation environment, we first guessed at physical fluid properties (increased density, viscosity, and drag constants) that we thought would represent our vegetated mat network. Then, after our 44-unit prototype network was built in the wave lab in Summer 2021, we were able to reverse-engineer more accurate physical fluid properties from observed physical performance in the lab. To put our assumptions and numerical representation techniques to the test, we used our research from the wave tank experiments conducted at the O.H. Hinsdale Wave Tank Research Facility to verify results through our many trials with different network configurations and wave types. Proving that our numerical model can accurately reproduce the observed network behavior in any wave condition is a critical step in confidently showing the efficacy of a given network in situ.

This model was developed using standard fluid surface-resolving mathematics (Navier-Stokes shallow water equations, Boussinesq approximations, a no-slip lateral boundary, and a finite-difference scheme) and was run on a supercomputer. These standard equations are applicable to many different scenarios including atmospheric flow, coastal dynamics, and river and channel flow.

Critical to the development of our research was the ability to determine how well the network performs its primary function in a controlled laboratory environment. To do this we traveled to the O.H. Hinsdale Wave Research Facility at Oregon State University in the Summer of 2021. Like a waterpark wave pool, the wave tank research facility is a large water-filled basin that produces controlled waves. However, instead of screaming children and flying pool noodles, this wave tank is equipped with data collection devices to monitor statistics such as wave height, water pressure, water velocity, and tension force. It’s also equipped with optical sensors which provide a precise visual record of unit movements in three dimensions.

To execute this experiment, we constructed 44 half-scale prototypes with representative materials such as tulle fabric and rainscreen to represent emergent vegetation and seaweed. We ran 32 different experimental test trials varying the wave period, wave height and network configuration to generate thorough results. We equipped the wave tank with Acoustic Doppler Velocimeter, wave gauges, infrared cameras and force sensors to collect the desired data.

With over a month spent constructing, testing, and rearranging the prototype networks, we collected terabytes of data. Initial results proved the effectiveness of our design by demonstrating that small, short waves can be reduced by up to 90% of their original height. The tests also confirmed our hypothesis that the wave attenuation capacity is a function of the network configuration and initial (incoming) wavelength. The collected data showed that when waves were smaller than the size of the mats, the network was highly effective at wave dampening. This effectiveness decreased with an increase in wavelength, but did not drop to zero until wavelengths were approximately 8 meters, or the aggregate size of all 4 rows. These results have been significant to our team and provided a crucial step in our continued research. Of course, we must remember this is a controlled laboratory experiment that comes with its own opportunities and constraints. While the wave generator allowed us to test very specific conditions, the boundaries of the wave tank created results that would not be experienced in an unconstrained coastal environment. Using our numerical model and control tests, we are working towards removing reflections in the data to remove these impacts and refine our model. See the full results published in Frontiers Built Environment, “The Emerald Tutu: Floating Vegetated Canopies for Coastal Wave Attenuation”

We installed our first full-scale prototype in East Boston Harbor in May 2021, leaving it in the water until the end of October. For this prototype test, we intended to assess the durability of the materials, the integrity of the unit design, and the health of the planted and volunteered ecology.

With sewing needles, burlap and a large pile of woodchips in hand, we began the dirty work of installing a massive mat of biomass amidst the abandoned piers of East Boston. It was hard work and a great demonstration of the need to manage the site and natural exigencies; however, through working with the tides and weather, we had our first full-scale prototype afloat and installed!

Over the course of the summer and fall, we made several trips to monitor the state and changes of the prototype:

T=6 weeks (mid July): Approximately 6 weeks after installation, we observed significant growth of the planted marsh grass and substantial colonization by aquatic organisms. It was also clear that the shape of the mat had deformed, becoming more elongated and reducing the surface area above the water line.

T=9 weeks (early August): Several weeks later, we noted that while the marsh grass was still growing, it appeared it had been grazed and therefore was much less abundant. Evidence of bird visitation in the form of severed shoots and digested shells was observed. The shape of the mat appeared to be the same and the materials were still intact.

T=12 weeks (late August): After a few more weeks, the remaining marsh grass organisms appeared to experience significant regrowth and were much taller than the last visit. For this visit, we acquired a GoPro camera to document the status of the mat below the water line. The videos were spectacular and allowed us to start identifying several of the submerged species

T=16 weeks (early October): During this visit, we observed that the mat was nearly entirely submerged and much of the organism growth had slowed. While there was still sea lettuce growth near the top of the mat, the marsh grass was below water and had experienced significant stress.