Coastal morphodynamics
Study of coastal landform interactions with physical processes.
Coastal morphodynamics looks at how coastal landforms and physical forces like waves, tides, currents, wind, sediment movement, and storms interact. Shorelines change over both short and long periods through gradual and sudden shifts driven by linked factors such as water motion, environmental conditions, and local rock types. The field relies on field observations and models to study coastal systems and predict future changes.
Quick Facts
- Key researchers
- Lynn D. Wright and Bruce G. Thom
- Year of early formalization
- 1977
Facts from the source article.
Origins of coastal morphodynamics
Early investigations of coastal morphodynamics were published by Lynn D. Wright and Bruce G. Thom. This work helped formalize the study of coastal landform change. Field observations of coastal landforms, such as sand dunes and estuaries, were conducted to document sediment transport and shoreline morphology. A basic conceptual model linking interconnected factors influencing coastal evolution was developed, emphasizing the interaction between geomorphology and hydrodynamic processes to predict effects of dynamic change.
Beach types
Dissipative beaches are flat with fine sand; waves break far from the intertidal zone and dissipate force progressively along wide surf zones. They have a wide shoaling and surf zone and are characterized by spilling breakers. Reflective beaches are steep with coarse sand, lacking a surf zone; waves break brusquely on the intertidal zone. Coarser sediment allows percolation during swash, reducing backwash strength and enabling deposition in the swash zone.
Morphodynamic processes
Beach states shift primarily due to changing wave energy. Storms, for instance, drive sediment offshore under steeper waves, flattening a reflective beach profile into a more dissipative one. These morphodynamic processes also shape other coastal features, like spur-and-groove formations on coral reefs and tidal flats within infilling estuaries. The relative strength of near-bottom currents—driven by incident waves, subharmonic oscillations, infragravity oscillations, and mean longshore and rip currents—depends on the beach state. On reflective beaches, incident waves and subharmonic edge waves are the main forces. In highly dissipative surf zones, incident waves decay shoreward while infragravity energy grows; infragravity standing wave currents then dominate the inner surf zone. For intermediate states with bar-trough topographies (straight or crescentic), incident wave orbital velocities usually prevail, but subharmonic and infragravity standing waves, longshore currents, and rips also play significant roles. The most powerful rips and their feeder currents occur alongside intermediate transverse bar and rip topographies.
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