The Coastal System

Coasts can be studied in several different ways dependent upon their classification:

•Erosional or depositional

•Sediment type (clastic: shingle and sand; or muddy)

•Submergent or emergent

•Tectonic setting

•Process-based: wave dominated, tide dominated and wind dominated - the agents of erosion

The Study of Coasts

Wave Dominated Tide Dominated Wind Dominated

Shore Platforms Mudflats Sand DunesCliffs SandflatsBeaches Salt MarshesSpits, Tombolos MangrovesDeltas Deltas

High Low

Energy

(French, 1997)

•Questions & Answers

•Cause and Effect

•Knowledge & Understanding

Coastal Processes

Wind, Waves, Tide, Currents

Sediment Movement

Coastal Form Dynamic over Space & Time

Weathering, Erosion, &Deposition

Equilibrium

The Coastal System

WAVES WINDTIDES

GEOLOGICAL STRUCTURE

Cliffs and Shore Platforms

Coral Reefs Beaches

Sand Dunes

Mudflats

Dominant Less DominantMarine

Terrestrial

Coarser Finer

MATERIALS

ENERGY

(Hansom, 1988)

Coastal Systems:

coastal systems vary primarily in response to wave intensity and tidal currents

breaking waves (and resultant currents) provide most of the systemic energy

several additional factors also influence coastal processes and landforms

original geology of the coastline

relative 'erodibility' of regional bedrock

sea level variations (global and local tectonic or glacio-eustatic changes)

coastal systems typically characterized as erosional or depositional

erosional or depositional nature of any coastline varies with the systemic energy

The Coastal System

Weathering & Erosion

What is?Weathering: Breakdown of rock (Geology) to form sediment in situ

Weathering is a set of physical, chemical and biological processes that alter the physical and chemical state of rocks and soil at or near the earth's surface. Rock and soil is altered physically by disintegrating and chemically by decomposing. Nearly all weathering involves water, mostly directly: frost shattering, wetting and drying, salt weathering, and all chemical weathering is in solution. That is, weathering is climatically driven and thus the term weathering. Because weather and climate occur at the earth's surface, the intensity of weathering decreases with depth and most of it occur within less than a metre of the surface

of soil and rock.

Erosion:Transport of weathered material from one location to another...The wearing away of land or the removal of beach and/or dune sediments by wave action, tidal currents, wave currents, drainage, or wind. Erosion includes, but is not limited to, horizontal recession and scour and can be induced or aggravated by human activities.

Erosional & Depositional Coastal Landforms