Greening the Gray

Mitigating the impacts of centuries of human coastal development and the increasing impacts of climate change will require a multitude of approaches to meet the challenge of fostering healthy coastal ecosystems. Balancing a desire for improved ecosystem function with the traditional and emerging needs of coastal economies has led to the search for methods of ‘greening gray infrastructure’ within urban ocean zones. The Port of San Diego has deployed one such project, using cast concrete coastal armoring units (‘COASTALOCK’ blocks) that serve the function of traditional rock riprap for armoring harbor shores, but also provide a more complex physical structure intended to create more favorable habitat for shoreline organisms. The pilot deployment was installed in 2021, and the two year initial monitoring period of settlement of intertidal species on the blocks came to a close in early 2023. The Port of San Diego is continuing to weigh whether a further expansion of the COASTALOCK armoring units would meet the desired goals of providing durable coastal armoring while increasing biodiversity and productivity on armored shores, and is relying in part on the evaluation of the benefits to the biological communities associated with those shores. USC Sea Grant has funded a study to formally evaluate the functionality of COASTALOCK armoring units for creating more thermally-favorable habitat that will permit occupation by a broader array of species than traditional rock riprap.