GROWING ISLANDS
PROTOTYPING ● RESEARCH ● INTERDISCIPLINARY TEAMWORK ● ILLUSTRATION
More details on skills
Sandbar formation using natural wave forces
10 month project with MIT's Self Assembly Lab, Fall 2018 to Spring 2019, Cambridge, MA, USA
Team of 5 researchers across several engineering disciplines under the supervision of Professor Skylar Tibbits
Research presented by Professor Skylar Tibbits at an April 2019 TED Conference linked here
CONTEXT
Rising sea levels are slowly eroding shorelines across the world. Currently, shorelines are either protected with man-made walls or augmented through dredging. Both methods are harmful to the ecosystem and provide only temporary solutions against a powerful and dynamic force of nature.
MIT’s Self-Assembly Lab was tasked with finding a more environmentally friendly solution to protect the eroding shorelines in the Maldives on the island Emboodhu Finolhu.
RESEARCH
Research was conducted primarily through industry expert interviews to better understand sediment transport and wave dynamics. Sandbars form naturally when sand bed configurations cause enough sediment transport to build up and emerge above the water. We identifies four key naturally occurring geometries that could trigger sediment transport.
We also conducted research on the wave environment of the targeted test site in the Maldives to understand how to simulate an accurate testing environment.
Sheer stress effect
SEDIMENT TRANSPORT
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SEDIMENT TRANSPORT
Channel effect
SEDIMENT TRANSPORT ILLUSTRATION
SEDIMENT TRANSPORT
Drop off effect
SEDIMENT TRANSPORT
Geometries were rapidly prototyped using 3D printing, laser cutting, and sewing. They were tested in the wave tank under wave conditions we programmed to simulate the Maldives.
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WAVE TANK TEST GEOMETRY
Sediment transport around comb geometry
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WAVE TANK TEST GEOMETRY
Sediment transport around X shaped geometry
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WAVE TANK TEST GEOMETRY
Sediment transport around comb geometry
TESTING
We built a 2’ x 6’ wave tank programmed to simulate different wave environments specifIc to the Maldives in terms of wave frequency and amplitude.
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Wave tank built for testing with robotic arm programmed to generate wave dynamics
Geometries were rapidly prototyped using 3D printing, laser cutting, and sewing. They were tested in the wave tank under wave conditions we programmed to simulate the Maldives.
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WAVE TANK TEST GEOMETRY
Sediment transport around comb geometry
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WAVE TANK TEST GEOMETRY
Sediment transport around grid shaped geometry
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WAVE TANK TEST GEOMETRY
Sediment transport around comb geometry
The most successful geometry was a 5” x 4” x 10” canvas ramp that resulted in a significant accumulation of sand after 40 minutes of testing the ramp in the wave tank.
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USE CASE
Given the successful results of the ramp geometry, here I have illustrated how we think the ramp geometry could be used to build sandbars on the shorelines of the Maldives.
1. Ramp is placed partially submerged on the sand bed with the tall end facing the desired location for sand accumulation
2. Water passing over the ramp drops off the edge creating turbulence displacing and accumulating sand at the base of the ramp
3. When fluid flow has enough velocity to create a shear stress effect, sand is transported over the ramp accumulating more sand at the base of the ramp
We conducted research to understand where the most effective locations to place a geometry to instigate sediment accumulation would be within the lagoon around the island Emboodhu Finolhu.
Here I have illustrated wind roses to inform placement of geometries by season to best facilitate sandbar formation. Objects are ideally placed in areas where wind can facilitate wave turbulence to push sand over the ramp allowing sand to accumulate over time.
SPRING USE CASE
Wind environment based on March
SUMMER USE CASE
Wind environment based on May
AUTUMN USE CASE
Wind environment based on September
WINTER USE CASE
Wind environment based on January
ON SITE TESTING
In early 2019, we had the opportunity to conduct some on site testing in the Maldives. We scaled up the canvas ramp by 15X measuring at 0.6 x 0.6 x 1.2m. We used sail canvas and thread to sew together 8 ramps for testing. The canvas and thread were made of natural fibres that could harmlessly biodegrade in the ocean over time.
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Sewing on site testing canvas ramps to be filled with sand
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Sewing on site testing canvas ramps to be filled with sand
The first round of on-site testing occurred in February 2019 and is documented in the TED Talks video linked here. Results showed that after 4 months, the sand bed height around the canvas ramps had increased by 0.5m.
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On site barge filling canvas ramps with sand
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Day 0
Initial installation
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Day 120
Sand bed height increased by ~0.5m
TED TALKS
Professor Skylar Tibbits presented project findings and continuing progress as "A new way to grow islands and coastlines" at a TED conference in April 2019.
