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