HUMAN INFLUENCE ON BARRIER ISLAND AND OYSTER REEF EVOLUTION

Barrier islands and oyster reefs are critical components of dynamic coastal systems, providing natural resiliency and coastal protection, yet both are increasingly altered by human activity. The aims of this dissertation are to: (1) quantify the long-term geomorphic impacts of barrier island management on washover flux and island persistence, (2) assess how human-driven land-use change alters oyster reef sedimentology and persistence, and (3) identify universal patterns of natural oyster reef growth and geometry to guide the design of resilient living shorelines.Objective 1 was addressed by analyzing decadal-scale remote sensing data along a 30-km stretch of northern Hatteras Island, North Carolina. Results show that dune and road maintenance reduce washover flux and extent by ~50%, constraining natural barrier rollover and accelerating island vulnerability. Objective 2 was addressed by comparing core sediment records, geochronology, and satellite imagery from natural intertidal oyster reefs in two estuaries with contrasting LUC histories and environmental settings. In the Newport River, major LUC led to mud-dominated reefs, marsh encroachment, and reef decline. In contrast, reefs in the more tidally flushed White Oak River maintained sandy substrates and active oyster populations, highlighting the role of hydrodynamic setting in mediating human impacts.Objective 3 was addressed using multi-core transects and geochronology to document reef growth over centuries. Results reveal consistent patterns of lateral and vertical reef accretion, with reefs evolving into shore-perpendicular geometries near mean high water. Trajectories diverged under different environmental regimes in the three NC estuaries, with low-flow, fine-sediment systems prone to marsh takeover and tidally flushed, sandy systems supporting reef resilience. These findings can inform living shoreline and restoration reef design and site selection to align with natural growth patterns and environmental conditions that promote long-term success.Overall, this research shows that human management decisions, whether through shoreline stabilization, watershed land use, or reef restoration design, can influence the long-term resilience of coastal systems from barrier beaches to estuaries. By incorporating lessons from natural barrier islands and oyster reefs, managers can better balance protection of people and infrastructure with the long-term sustainability of these critical coastal environments.