Coasts

By: Sergio Gutierrez Fernandez

Waves’s origin-From submarine earth

movements, and by the wind

blowing over the sea.

The size of a

wave depends

on: 1-Strength of the wind2-Length of time that the wind blows3-Distance of sea that the wind has to cross

As a wave approaches

Its base is slowed down by

friction against the sea-bed. The

top of the wave will then move

faster, increase in height and

will eventually break onto the

beach.

Longshore drift-The movement of material along a beach

Coastal Erosion -Hydraulic action: The waves trap and compress

air in cracks and holes in a cliff-Corrasion: Large waves hurling beach material against the cliff-Attrition: When waves cause rocks and pebbles on the beach to bump into each other and to break down in size-Corrosion: Cliff is slowly dissolved by acids in the sea-water

Transportation

along a beach-Waves rarely approach a beach at right-angles. They usually approach at an angle that depends upon the direction of the wind

Groynes

-Longshore drift can

sometimes affect human

activities. In response,

people may erect wooden

breakwater fences down

the beach, they reduce the

force of the waves

Swash

-The water that rushes up a beach after a wave breaks.

Backwash-When this water returns down the beach to the

sea.

Deposition

Occurs:In sheltered areas where the build-up of sand and shingle is greater than its removal.

Spits

-Is an area of sand or shingle which either extends at a gentle angle out to sea or which grows across a river estuary.

The Beach -Is the most

widespread coastal deposition feature

The Beaches Are

Formed-By erosion, sand and shingle beaches result

from deposition.

Bars-Is a barrier of sand

stretching across a

sheltered bay.

Bars may form in several ways

1- When a spit is able to grow right across

a bay.

2- When a sand bank develops some

distance off the shore, but parallel to it

Cliff Erosion Causes:

Effects:

-If resistant rock, waves erode at their base causing them to become unstable and to collapse-If less resistant rock, rain can wash loose material down to the cliff base. It can be rapidly removed by waves.

-Villages, farms and campsites

situated in places that a few

years ago were considered

safe, have been abandoned

and lost.

Human

Responses-The natural rate of cliff erosion can be accelerated by human activity. There

are arguments for and against trying to protect cliffs from erosion.

Storm Surge:-Occurs when the

level of the sea rises rapidly to a height

well above that which was predicted.

Factors Combined to cause a storm surge:

1-An area of low atmospheric pressure

(depression)

2-The further 2-metre rise in sea-level, especially

in river estuaries

3-Time of spring tides, when the tides reach their

highest level

4-Rivers flowing into the North Sea were in flood

but could not discharge their water due to the

high sea-levels.

Causes of Coastal

Flooding 1-Land behind the coastline is flat and low-lying2-Severe storms can cause exceptionally high waves and create storm surges3-Very high tides can flood areas that are not protected either naturally (by sand dunes) or artificially (by sea-walls)4-Global warming is causing sea-level to rise, so increasing the flood risk in many low-lying coastal areas around the world

Precautions in Coastal Flooding

1-Building of higher and stronger

sea-walls (expensive and regular

maintenance)

2-Build tidal barriers across river

estuaries

3-Stop building on coastal flood

plains

4-Improve weather forecasting

and early flood warning systems

5-Try to reduce the increase in

global warming

The End