coasts. theme overview coasts coastal processes coastal landforms coastal management
TRANSCRIPT
COASTS
Theme Overview
Objectives define terms associated with coasts
describe the relationship between wave energy and fetch
explain how swash and backwash is formed.
describe the characteristics of constructive and destructive waves.
Define: CoastIt refers to a zone where land meets
and interacts with the sea.
Microsoft Office PowerPoint 97-2003 Prese
AGENT 1WAVES
Define: Waves
Waves: refers to a rising and falling movement of the water surface.
It is produced by winds blowing across the ocean or sea.
R/Ship: Erosion & Waves
The extent of erosion depends on the energy of the waves.
Factors affecting wave energy Wind Energy Fetch
Factor: Wave Energy
Wind Energy
The greater the difference in pressure, greater the wind speed.
The greater the wind speed, larger the waves and greater the extent of erosion.
Factor: Wave Energy
Fetch
This refers to distance over which wind blow across open water to form waves.
The longer the fetch, the larger the waves and greater the extent of erosion.
Types of Waves
Swash
Backwash
Waves approach the coast
Shallow sea bed causes friction
Friction causes loss of energy
Waves (back) pushes waves (front)
Waves (front) forced to rise
Waves collapse and breaks
SWASH!!!
DEFINITION: SWASH
This refers to the forward movement of a wave onto the beach.
Swash brings materials to the beach. Hence it is also known as constructive waves.
Swash moves up the coast
Wave energy is gradually lost
Gravity pulls the wave back
Waves move back into the sea
BACKWASH!!!
DEFINITION: BACKWASH
This refers to the backward movement of waves into the sea.
This causes the removal of materials from the beach. Hence it is also known as destructive waves.
Constructive Vs Destructive
Waves
DESTRUCTIVE WAVES
Large, high waves Common on steep coastal slopePlunging over when breakingMore powerful backswash than swash Erodes coasts
CONSTRUCTIVE WAVES
Small, low waves Common on gentle coastal slopeSpilling over when breakingBuilds coast up by deposition