Lesson ObjectivesLesson Objectives

This lesson is looking at the different types of wave you can get and how they effect the coast differently.

By the end of the lesson you should be able to:

Name the two types of wave

Describe the differences between them

Explain how they change the coastline in different ways.

What is the definition of a coastline?

The coast – a narrow zone where land, sea and atmosphere meet

Swash and Backwash!

Swash

Backwash

Constructive WavesSwash

Backwash

Material deposited on beach

Destructive Waves

Swash

Backwash

Material eroded off beach

Destructive waves mean steep, stepped beach caused by waves pulling sediment off the beach

Constructive waves mean wide, flat and usually sandy beaches as waves deposit sediment on the beach

Constructive Waves

Destructive Waves

Constructive and Destructive WavesConstructive and Destructive Waves

ConstructiveConstructive• Height = Low (less than 1

metre)

• Length = Long

• Frequency = Fewer than 10 a minute

• Energy = Low

• Beach gradient = flat

• Main process = deposition

• Stronger swash

DestructiveDestructive• Height = High (more than 1

metre)

• Length = Short

• Frequency = More than 10 a minute

• Energy = High

• Beach gradient = steep

• Main process = erosion

• Stronger backwash

Key WordsKey Words

Fetch – the distance a wave has travelled

Swash – the forward movement of a wave up the beach after the wave has broken

Backwash – water from a breaking wave which flows under gravity down the beach

Constructive Wave – deposits sediment, building up the beach

Destructive Wave – a wave that removes sediment from the beach, eroding it.