SIGNATURES OF RESILIENCE IN HUMAN-ALTERED COASTAL SYSTEMS

More than 85% of the world's coastline has been somehow altered by human activities. These activities and their consequences are concentrated in the Low Elevation Coastal Zone: a ribbon of coastal land below 10 m elevation that hosts as many as 1 billion people and a disproportionate share of the planet's physical infrastructure. Such pronounced exposure of people and infrastructure along low-lying coastlines means that these environments sustain severe impacts from coastal hazards (e.g., erosion, storm surge, flooding, sea-level rise). Moreover, population growth, infrastructural expansion, and climate change only make hazard impacts worse.

As coastal risk - defined as the exposure of people and infrastructure to natural hazards - has increased, so has broad scientific interest in coastal resilience, as an alternative to conventional engineering approaches to protecting human-altered coastlines from natural hazards.

Here, coastal resilience is defined as how a coastal system - the physical, ecological, and human components of a coastal environment, and the relationships among those components that sustain their functioning - recovers from disturbances, like extreme storms, over time. At the seaward edge of the Low Elevation Coastal Zone, environments characterised by beaches, dunes, floodplains, and wetlands take their physical shape from the storm events that they absorb. Despite their precarity to natural hazards, many low-lying coastlines are extensively built upon and intensively altered by human activities. However, human-altered coastlines are almost never examined as dynamic environments in their own right.

Understanding human-altered coastlines as dynamic systems is essential to predicting hazard impacts, anticipating effects of climate change, and reducing coastal risk. Previous work has used computer modelling to suggest that unlike their natural counterparts, human-altered coastlines evolve over time to become increasingly vulnerable to storm damage and functionally dependent on engineered hazard defences - thus rendering them less resilient than natural barriers. But that difference in how human-altered and natural coastlines evolve, and what that means for their resilience, has not yet been demonstrated and examined with observations and measurements from real places. This project addresses that gap, by testing theory with empirical evidence.

The aim of this project is to identify and measure indicators of resilience in human-altered and natural low-lying coastal settings around the world - all at the exposed, seaward edge of the Low Elevation Coastal Zone - using new methods for analysing decades of satellite imagery. I will measure the physical "signatures" that distinguish human-altered from natural coastlines, relate those physical signatures to patterns of coastal development over time, and combine that information to determine the relative "stability" of these human-altered versus natural coastal settings. This project will be first to quantify coastal resilience this way, and at this scale, derived entirely from observational data from real settings.

Overall, with its focus on human-altered coastlines and its novel analytical approach, this project will deliver new, observation-driven insights into resilience in vulnerable low-lying coastal environments worldwide. The methods and findings that emerge from this project will enable future interdisciplinary research into how coastal resilience could be deliberately enhanced in targeted, efficient, effective ways to reduce coastal risk.