Building Land to Know How It Erodes Away

[Top image: Sediment-thickness map, showing thickness of the sand deposit at Hewes Point, north of the Chandeleur Island chain. Sand used to construct the E-4 berm was excavated from the side of the deposit, about 3 kilometers north of the islands. Bottom: Photograph taken on April 13, 2011, of the completed E-4 berm, detached from the islands for the first 8 kilometers (13 miles), beyond which it was constructed on the beach to reduce required sand volume.]

In the aftermath of the Deepwater Horizon Spill, the USGS and other agencies have been experimenting with building massive islands, or “oil-spill-mitigation berms” placed stratigically between the disappearing Mississippi Delta and the very large array of off shore oil rigs.  The USGS reports:

“The berm and the northern Chandeleur Islands provide a natural [..?] laboratory of unusually large scale to observe how sudden changes in morphology (for example, due to storms or renourishment projects) and geologic processes (such as erosion, deposition, and rollover—the landward movement of a barrier island as sediment is eroded from the seaward side and deposited on the landward side) will affect barrier-island evolution. With the wealth of scientific data already available for the islands and the fact that the berm will interact with the barrier-island system on observable time scales, the USGS hopes to answer fundamental questions about how climatic and geologic variables influence the present and future morphology of coastal systems. Understanding the physical interactions that drive coastal evolution provides a framework of knowledge for effective management of coastal planning, protection, and restoration.”

“…One goal of the study is to identify how these variations between sediment composition of the berm and the island change the natural response of the island system to physical processes. In an ironic twist, since the berm’s completion in March 2011, the erosion of the berm is being influenced by the island chain.”

Sand castles on a grand scale; the anthropocene continuing to articulate accelerated feedback loops of its own partial agency.

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