3. Factors Governing the Work of Waves and the Character of Coastal Landforms
● Types of wave action
→ waves that break against the land are associated with wave erosion.
→ waves which break before reaching the shore are associated with wave deposition
→ constructive and destructive waves
● Geology of Coastal Rocks
→ type of rocks
→ resistance of rocks to weathering and erosion
→ direction of dipping of the rock strata
→ presence, absence and arrangement of lines of weakness (e.g. joints, fissures, faults)
● Relief of coastal slope
→ steep coastal slope is associated with wave erosion because waves, especially those driven
by strong winds over long fetch, reach the coast in deep water and break against the land or cliff
side
→ Gentle coastal slope is associated with wave deposition as waves are retarded by friction with
the bottom of the slope in shallow waters. The waves tend to break before reaching the coast
● Orientation of the coast
→ The position of the coast in contrast to open sea or ocean determines whether the coast is
exposed to oncoming winds that have blown over long fetch or not
→ the aspect of the coast in relation to strong prevailing winds determines whether the coast is
exposed to high energy waves
→ exposed coasts are more susceptible to wave erosion
→ sheltered casts are more favourable to wave deposition
● Relative changes in Sea level
→ may result either
a. from a rise of the mean sea level or submergence/sinking of the coastal land or
b. from a fall of the mean sea level or emergence/uplift of the coastal land
→ Effect of glaciation in coastal areas the drowning of glaciated valleys when sea level rises
→ Effects of Volcanic activity in Coastal Areas occurrence of tsunamis, in relation to volcanic
activity, increases rate of coastal erosion
→ Effects of coastal growth in coastal waters coral growth offshore tends to dissipate energy
before waves reach the coast, thus helping to protect the coastline.
→ human impact modifies the natural coastal landscape by activities like reclamation,
construction works, dredging, building typhoon shelters and groynes
The Work of Waves and Resulting Coastal Landforms
● Wave refraction is the bending of wave fronts as they approach a shore so as to break
almost parallel with the shore. In deep water, wave fronts are essentially parallel to one
another. As they approach the shallow waters of the shore, the retarding influence of
shallow water or frictional drag with the sea floor, causes the waves to slow down and
the wave fronts to bend. Wave refraction occurs when:
→ along an irregular coast the retarding influence of shallow waters off the headlands before