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Ecological Seawalls and Breakwaters: the hard habitats of coastal armoring

The Hard Habitats of Coastal Armoring

 

Hard (Adj.)                

– solid, firm, and rigid

– requiring a great deal of endurance or effort

 

Ecology is not always soft, vulnerable, weak, and on the verge. Many marine species are inherently, resilient, tough, and tenacious, often existing in the most turbulent, deepest, and hardest of places. Similarly, coastal infrastructure such as seawalls and breakwaters that employ solid, firm, and rigid materials to armor coastlines are sometimes amenable to the habitat needs of marine species. This is the realm of hard habitats – a reconciliation of urban armature and marine ecosystems through the design of advanced structures that protect against rising seas and storms while providing habitat and refuge for marine species. This essay explores the scale, scope, and future outlook for the design of hard habitats in urbanized marine environments, and points towards the productive collaboration between marine scientists, materials research, and designers. For landscape architects and urbanists concerned with the ecology of cities, hard coastal infrastructure provides an exciting frontier through which to explore the built ecologies. For marine ecologists and other scientists, the fabrication of novel urban intertidal ecosystems provides new sites for experimentation and testing. This convergence of expertise and knowledge is occurring at exactly the moment when coastal infrastructure promises to multiply exponentially around the world, making the development of resilient and environmentally sensitive armoring especially salient. Many of the advances in hard habitat creation have focused on seawalls and breakwaters. Integration of marine habitat requirements with hard coastal infrastructure such as seawalls and breakwaters promise to incrementally improve, or reconcile, the ecology of urban marine environments.

Heterogeneity, Biomineralization, and Biofilms: key features of Hard Habitats

Habitat complexity and heterogeneity are central to the recruitment and diversity of marine species. The habitat structure and complexity of natural oyster reefs has been shown to increase nekton (i.e., swimming organisms) diversity and abundance in comparison to mudflats, though among oyster reefs with variable complexity, abundance is reported to remain stable (Humphries et al.). Niche theory posits that the number of species associated with a particular habitat increases with the number of fundamental niches. The diversity of niches allows for structural overlap and therefore an increase in species diversity. Rebuilding complexity in habitat is therefore essential in restoration and reconciliation efforts (Loke, Ladle, et al.). One way to rebuild complexity is by creating heterogeneity in abiotic conditions such as surface topography, salinity, light, and sediment. Even factors such as the movement or water, and the resulting “wave-scapes” created by heterogeneous surfaces, can impact the distribution of species as well as the morphology of anthropogenic coastlines (Kozlovsky and Grobman).

Successful examples of artificial marine habitats are now abundant in scientific literature, making it possible to derive a set of generalized design principles; 1) The heterogeneity of a surface, and formal complexity of a structure increase the potential spatial niches that can be occupied by marine species, 2) Marine structures impact the environment across scales, making it important to consider the detailed rugosity and porosity in small patches in addition to the overall horizontal and vertical profile, 3) Design details that increase variations in moisture, salinity, light, texture, and temperature, are often beneficial to species diversity by creating varied abiotic conditions, 4) Materials play an important role in species establishment and colonization through the creation of biofilms, and processes of biominerology, and variability in materials can positively impact species diversity, 4) Mimicking naturally, and locally, occurring forms, processes, and materials can improve the suitability of a structure. Although each new project will require knowledge of local ecology and coastal processes, these criteria establish a starting point for design development, and a lens through which to evaluate the ever-growing list of pilot projects and new technologies.

 

Ecological Sea Wall Prototypes (UC Berkeley Spring 2017)

LDARCH 226 – Innovation Seminar

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