7 - Coastal sediment transport
from Part II - Coastal Processes
Summary
Synopsis
Modification of the coast takes place through the erosion, transport and deposition of material that is either eroded by waves and currents or brought to the coast, e.g., by rivers. Fine sediments in the silt and clay size range do not occur in appreciable amounts in the inner nearshore and surf zones on energetic coasts. They tend to be placed in suspension and diffuse uniformly through the water column. They are then removed offshore or alongshore where they settle out of suspension in deep water in the outer shoreface or further offshore. Fine sediments may also be brought into estuaries, bays and lagoons where they are deposited in quiet water, often promoted by the presence of vegetation such as seagrasses, salt marsh plants and mangroves. Coarser particles of sand and gravel are exchanged readily between the inner nearshore and surf zones and the beach, and may be transported alongshore in appreciable quantities. It is usual to distinguish between processes that lead to the net transport of sediment onshore or offshore (shore normal transport) and those tending to move sediment alongshore (longshore sediment transport), though both processes occur simultaneously.
Except in a few locations in the surf zone, such as rip channels and where longshore currents are fastest, unidirectional currents in the nearshore and surf zone are generally not strong enough to erode and transport coarse sediment directly.
- Type
- Chapter
- Information
- Introduction to Coastal Processes and Geomorphology , pp. 139 - 180Publisher: Cambridge University PressPrint publication year: 2009
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