Coastal and Aeolian Processes

Waves, tides, and currents shape coastlines while wind reworks sand in deserts and along shores, producing dynamic landscapes of beaches, cliffs, and dunes.

Definition

Coastal processes are the actions of waves, tides, and currents that erode, transport, and deposit sediment along shorelines, and aeolian processes are the actions of wind that entrain, transport, and deposit sediment, chiefly sand, to build dunes and related landforms.

Scope

This topic covers the geomorphic processes at the land–sea margin and those driven by wind: wave erosion and longshore transport, the formation of beaches, spits, and barrier systems, and aeolian sand transport and dune formation. It addresses the most mobile and rapidly changing of surface environments.

Core questions

• How do waves and currents erode coasts and move sediment along shore?
• How does wind transport sand and build dunes?
• What controls the form and stability of beaches and dune fields?

Key theories

Physics of blown sand

Bagnold established the mechanics of wind-driven sand transport, including saltation and the formation and movement of dunes, founding the quantitative study of aeolian processes.

Coastal sediment budgets and longshore transport

Coastlines evolve according to the balance of sediment supplied, transported alongshore by wave-driven currents, and removed, so that beaches and barriers grow or erode depending on their sediment budget.

Mechanisms

Waves approaching a coast erode cliffs and shift sediment, and when they strike at an angle they drive longshore drift that moves sand along the shore to build beaches, spits, and barriers. Wind entrains loose sand by saltation, depositing it where flow decelerates to form dunes whose shape reflects wind regime and sand supply. Both systems are governed by sediment budgets that determine whether landforms grow or erode.

Clinical relevance

Coastal and aeolian process understanding is essential for managing shoreline erosion and flooding, designing coastal defenses and ports, controlling dune and desert encroachment, and anticipating the effects of sea-level rise on populated coasts.

History

Coastal geomorphology developed from early-twentieth-century shoreline studies, while Bagnold's 1941 work on blown sand created the modern physical basis for aeolian geomorphology. Both fields have since become highly quantitative and central to coastal and dryland management.

Key figures

• Ralph Bagnold
• Eric Bird
• Douglas Johnson

Seminal works

• bagnold1941
• bird2008

Frequently asked questions

What is longshore drift?

Longshore drift is the movement of sediment along a coast caused by waves approaching the shore at an angle, which pushes sand up the beach obliquely and lets it slide straight back, producing a net transport of material parallel to the shoreline.