18-13. The role of US coral reefs and reef restoration in reducing coastal risk

BACKGROUND: Coastal infrastructure is increasingly vulnerable to hazards from climate change. The mounting risk and costs of coastal flooding and storm-induced wave impacts to coastal communities are increasingly challenging traditional coastal engineering measures. Conventional grey infrastructure methods (e.g., sea walls and embankments) require costly maintenance, often have adverse environmental effects, and may be unsustainable with increasing risk. On the other hand, restoration or creation of ecosystems (i.e., green infrastructure) has been increasingly promoted as a more sustainable and cost-effective approaches to coastal protection, either alone or hybridized with grey infrastructure. 

Coral reefs, in particular, provide substantial protection to coastal communities by reducing wave height by approximately 97%. Recently, U.S. coral reefs were assed to provide coastal protection to more than 18,000 people and $1.8 billion in buildings and economic activity annually. The complex geologic reef structure created by corals, however, is degrading in many areas, reducing the coastal protection provided by this ecosystem and thus increasing the risk to coastal communities. Coral restoration has been proposed as a strategy to restore or upgrade the flood mitigation function of coral reefs. However, successful field demonstration projects for this application have been limited to date, and the question remains open about how to design coral reef restoration to deliver such protection. For restoration to effectively contribute to coastal protection, it needs to provide both resistance and resilience to disturbances to ensure its sustainability. These goals require scaling up beyond a strictly an ecological approach to include specific hydrodynamic and engineering considerations in reef restoration designs and to address multiple abiotic environmental processes at coastline, project, and coral scales.

Key design parameters of coral reef restoration projects for coastal hazard risk reduction include (i) where to site restorations and (ii) what size/shape restoration would effectively meet protection goals. These restoration questions encompass risk exposure and vulnerability for coastal assets, and also provide constraints on where restoration may be feasible or most effective. At the coastline scale (order of kilometers), the terrestrial landscape context includes shoreward locations of current and planned coastal assets and related economic valuations. Coastal assets include anthropogenic infrastructure (e.g., cities, ports, airports), as well as natural infrastructure, including biological (e.g., mangroves), and geological (e.g., reef morphology, shoreline topography). At the land-sea interface, the potential persistence of coral restoration can be influenced by terrestrial-based constraints (e.g., land-based pollution). At project scale (order of meters), the width, length, and height of the restoration and its influence on hydrodynamic processes (e.g., roughness, permeability) not only plays into its effectiveness for coastal protection, but also its cost for implementation, construction, and maintainance. These factors all play into cost:benefit analyses for accessing funding sources. At coral scales, the size, shape, and density of outplanted corals affects flow and hydrodynamic roughness, that, in turn, affects the wave attenuation performance of the restoration. All these scales represent challenges and frontiers of knowledge and practice before successful coral reef restoration is possible for hazard risk reduction. At the same time, our understanding of how these different factors work together over the various spatial scales and thus contribute to risk reduction is poor, and thus our ability to design and finance such nature-based projects is hampered. 

DESCRIPTION OF THE RESEARCH OPPORTUNITY: The goal of this research is to determine the role of corals and coral reefs in coastal hazard risk reduction, and how coral reef restoration may reduce the hazards to, and increase the resiliency of, the Nation’s coastal communities. This research opportunity is timely given (i) the growing momentum for nature-based solutions and (ii) the incipient research showing spatial benefits of coral reefs for coastal risk reduction that now allow considering reef restoration projects to protect specific communities at risk. 

The postdoctoral fellow will develop and test innovative means for measuring and predicting hydrodynamics (water levels and waves) over and amongst corals and coral reef structures (both pure “green” transplanted coral and “gray-green hybrid” transplanted corals on artificial substrate) using state-of-the-art process-response models and assimilations of disparate data types such as satellite-derived high-resolution topography and bathymetry, coastal geomorphology, and historic, real-time, and forecasted oceanographic measurements. We envision this research could be accomplished using a number of different approaches. First, theoretical numerical modeling of flow around individual transplanted corals or reef structures will better guide the design individual restorations in terms of spacing of corals or structures, cross-shore extent necessary to perform hydrodynamic functions, etc. Another approach will use previously-acquire topographic, bathymetric, and oceanographic information from field sites and use them to calibrate and validate process-based numerical models to be tested for different coral reef and shoreline configurations. This modeling will inform and guide where the restoration projects should be placed on the inner shelf to provide the greatest coastal hazard risk reduction as quantified in socioeconomic terms. These predictions will form the scientific underpinning to guide the development of coral reef restoration for coastal hazard risk reduction globally. 

The postdoctoral fellow will have ample opportunities for interdisciplinary collaborations in oceanography, physics, engineering, geospatial analyses, remote sensing, and numerical modeling. They will be able to develop partnerships with researchers from different USGS science areas, other federal agencies, and academia. The postdoctoral researcher will be at the forefront of interdisciplinary research, collaborate with a team leading global innovation in nature-based solutions, and will participate in significantly improving our understanding of the role of coral reefs as natural infrastructure to reduce the risk to, and increase the resiliency of, coastal communities in the US and US Trust Territories. 

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

Proposed Duty Station: Santa Cruz, CA

Areas of PhD: Oceanography, computer science, coastal engineering, civil engineering (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet the qualifications for: Research Geologist, Research Oceanographer, Research Computer Engineer 

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Human Resources Office Contact: Audrey Tsujita, 916-278-9395, atsujita@usgs.gov