Environmental Drivers of Coastal Evolution

Abstract

Coastal evolution is shaped by the processes that influence sediment transport at coastlines. The present morphology, sedimentology, and distribution of modern coastal landforms reflect the influence of Holocene environmental processes that have altered the availability and movement of sediment at the coast. In this thesis, I leverage sediment transport modeling, sedimentary field data, and geospatial analysis to constrain the influence of specific environmental drivers of coastal change since the last deglaciation. I present case studies from near-field (North Atlantic) and far-field (tropical Pacific) coastal environments. Chapter 2 models the effects of glacial ice retreat on surface hydrology and quantifies resulting effects on fluvial sediment transport, showing that landscape changes that accompany deglaciation shape the evolution of rivers and the delivery of sediment to the coast. Chapter 3 explores interactions between paleohurricanes and evolving barrier coastlines, examining how coastal development influences the deposition and preservation of sedimentary paleohurricane records that can be used to understand long-term storm recurrence. Chapter 4 reconstructs the influence of Holocene environmental processes on the development of Pacific atoll islands, demonstrating that both sea-level change and temporal variations in storm-driven sediment transport mediated the timing and pace of island formation. Chapter 5 examines processes affecting atoll island development at the regional scale, quantifying patterns in the distribution of islands on atoll reefs relative to local wave climates. Together, these chapters connect coastal sedimentary records and modern morphologies to environmental processes that have shaped coastal development. Through quantitative examination of coastal sedimentary environments, we gain insight into the influence of environmental processes on coastal development across timescales longer than permitted by historic observations. By constraining the magnitude and nature of environmental influences on coastal sediment transport, this thesis contributes to a broader understanding of how environmental change has shaped the evolution of coastlines.