Coasts

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Coasts

Coastal Processes

Deposition

Waves as an agent of deposition

Low-energy waves have a swash that is stronger than the backwash. this occurs on a gently slopping beach. When the backwash returns to the sea, some sediments are left on the coast. Low-energy waves are also called constructive waves.

Transport

Waves and currents as agents of transportation

Longshore Drift

Waves approaches the coast at an angle, the swash carries sediments up onto the coast at that angle. The backswash then carries the sediments back into the sea

Erosion

Waves as an agent of erosion

A wave is a rising and falling movement of the water surface.It is usually produced by winds blowing across the sea or ocean

large waves cause coastal erosion

High-energy waves have a backwash stronger than the swas.Causing more materials to be removed from the beach instead of being deposited.

Currents as agents of erosion

During low tides, the water retreats down the coast

During high tides, water extends up the coast.

Coastal Protection measures

Soft engineering

Soft Engineering is involves applying the knowledge of natural process to stabilise the coast and reduce erosion

Encouraging growth of coral reefs

Inffectivenesss

Corals can only grow well in clear waters

It requires constant effort from various groups of people

Reduces coastal erosion by reducing speeds of waves as they approach the shores.

Beach nurishment

Cost is high for beach quality sand

Lasts only for about 10 years

Adding large amounts of sand to a beach that have been eroded from a beach to replenish sand eroded by the longshore drift.

Planting Mangroves along the shores

As young mangrove trees are fragile, mangrove planting requires cooperation of the local people living in the area.

Planting mangroves helps to protect coasts from erosion as many moagrove trees have prop roots or kneed roots that anchor the tress frimly in the soil

Stabilising coastal dunes

Ineffectivenesss

Human activities sucha as property development ad recreational activities have to be minimised along these coasts

Effectivenesss

Planing vegetation such as marram grass along coasts, roots of vegetation trap and bind the sand together, preventing sand from being blown inland

Hard engineering

Hard engineering refers to the construction of structures such as seawalls, beackwaters, groynes and gabions

Gabions

Ineffectivesness

Gabions can be easily destroyed by powerfull waves during storms and the wire rusts easily.

Gabions are temporial features as they last ony to about 15 years whereas seawalls, breakwaters and groynes lasts for about 30 years. Gabions are much cheaper compared to other coastal protection measures such as seawalls, breakwaters and groynes.

Gabions are rocks stored in wire chages to form a wall to protect the coast from erosion and other coastal protection such as seawalls

Groynes

Ineffectives

The materials deposits by the longshore drift would not be replenished at the other side of the groyne. Hence the beach further down the coast may be eroded away.

A groyne is a low wall built at right angles to prevent materials from being transported away by the longshore drift .Transported materials accumulate on the side of the groynefaceing the longshore drift.

Breakwaters

breakwaters are granite walls built parallelto the coast. It creates a zone of shallow water between itself and the coast, such that the waves will break before reaching the coast.

Breakwaters are unable to provide complete protection as the leave areas of the coast unprotected, which are more prone to erosion.

Seawalls

Ineffectiveness

As waves break against the sea wall, the wave is redirected backwards resuslting in a strong backwash which would wear away the base of the seawall causing it to weaken and eventually collasp[e

Effectiveness

A seawall is usually made out of concrete, which absorbs the energy of the wave

Land Forms Produced by Coastal Processes

Tombolos

A tombolo is an extention of the coastline made up of mainly sand and other materials tha join an offshore island to main land

Spits

When longshore cirrents encounter a bay or a bend in the coast with shallow sheltered water, the materials will be deposited along the direction of the long shore drift.This is known as a spit.

Beaches

Beaches form when waves tides, or currents bring and deposits materials onto the shore.

Bays

Less resistant rocks froms bays

Headlands

More resistant rocks will form headlands

Formation of headlands

Cliffs and shore platforms

A cliff is formed when waves repeatedly pound against a rocky coast. Causing the weakend rocks to form lines of weakness. Waves erode the coast to cut a notch along the lines of weakness. The notch may be eroded to form a cave. The overhanging part of the notch or cave eventually collapses.