What are tetrapods and did their removal cause ‘unusual vibrations’ along Mumbai’s Marine Drive?

What are tetrapods and did their removal cause ‘unusual vibrations’ along Mumbai’s Marine Drive?

Subject : Environment

Section: Climate change

Context: Residents of two buildings on Marine Drive, the iconic 3 km promenade in south Mumbai, complained of ‘unusual vibrations” during high tide over the past weekend. It was result of the relocation of tetrapods as part of the ongoing Coastal Road Project.

What are tetrapods?

• Tetra pod in Greek means four legged. These are four legged concrete structures that are placed along coastlines to prevent erosion and water damage.
• It was first used in France in the late 1940s to protect the shore from the sea.
• They are typically placed together to form an interlocking but porous barrier that dissipates the power of waves and currents.
• These are large structures, sometimes weighing up to 10 tonnes, and interlocked tetra pods act as a barrier that remains stable against the rocks when buffeted by waves.
• Tetrapods, each weighing about 2 tonnes, were placed along Marine Drive in the late 1990s to break and dissipate waves and maintain the reclaimed shoreline in South Mumbai.

Why were the tetrapods removed from the Marine Drive area?

• They were temporarily removed to help carry out reclamation for the ongoing Coastal Road Project (10.58 km of coastal road from Princess Street in Marine Drive to the Worli end of the Bandra Worli Sea link. There are over 6000 terapods along Marine drive alone.