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Summary A Level Geography - COASTS Revision
This document is a collection of detailed notes on the Coasts topic including: beaches, system and processes, erosion, deposition, mass movement etc.
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3.1.3 Coasts3.1.3.1 Coasts as natural systems:
- Coastal environments are open systems.
- When there is a balance between the inputs and outputs then the system is in a state of dynamic
equilibrium.
- Positive feedback - moves system away from dynamic equilibrium (the equilibrium is upset) eg.
increased deposition on a beach
- Negative feedback - restores dynamic equilibrium
- A landform is a natural geographical feature or shape that appears on the Earth’s surface, created and
shaped by geological forces of nature eg. erosion and movement of tectonic plates. (single landform
feature)
- A landscape is a combination of landforms. It can be natural or manmade or both. (shaped by coastal
processes to create erosional and depositional landforms)
Inputs Components/stores Flows/transfers Outputs
● Energy from the ● Beach ● Longshore drift ● Dissipation of
waves, wind, ● Sand dunes ● Movement of wave energy
tides and sea ● Erosional sediment ● Accumulation of
currents landforms and ● Swash sediment above
● Sediment landscapes ● Backwash the tidal limit
● Geology of the ● Depositional ● Wind and water ● Sediment
coastline landforms and transport removed beyond
● Sea level change landscapes ● Erosional local sediment
processes cells
, 3.1.3.2 Systems and processes:
Sources of energy in coastal environments:
WIND
● Primary source of energy for other processes
● Important agent of erosion and transport
● Spatial variations in energy result from variation in the strength and duration of the wind -
persistently high and uninterrupted wind speeds means wave energy is likely to be higher. Most
coastlines have a prevailing wind which can be shortly interrupted by local weather patterns.This is
important as it is the one factor that controls the direction that waves approach and also the
direction the transport of material in the coastal zone.
● Fetch is the distance of open water which the wind blows uninterrupted by land obstacles. The shorter
the length of the fetch, the higher the magnitude and the energy of the waves.
● Wind is vital for waves formation. Waves are created by the transfer of energy from the wind blowing
over the sea surface (frictional drag). The higher the energy of the wind, the more energy is acquired
by the waves.
● Wind can also act as an erosion agent. It can pick up and remove sediment from the coast and then
use it to erode other features. (ABRASION)
WAVES (wave height, wavelength / amplitude, wave frequency)
● Once created by the wind, the waves are the primary agent in shaping the coast.
● Swash, backwash
● As waves approach shallow water, there is increased friction and the seabed and the base of the wave
begins to slow down. This increases the steepness and height of the wave until the upper part plunges
forward and breaks onto the shore.
Constructive waves Destructive waves
Low wave height High wave height with a steep form
Long wavelength (up to 100m)
Low frequency (6-8/min) High frequency (10-14/min)
Stronger swash than backwash Powerful backwash, weaker swash
Deposits material, material is constantly moved up Erode beach material
the beach leading to the formation ridges
Creates a steep beach profile because the waves Associated with steep beach profile - storm beach
are constantly depositing material
Wave refraction:
- Waves reflect the topography of the coastline and become increasingly parallel to the coastline. This
is called refraction.
- Wave approaches and it tends to drag in the shallow water which meets the headland. This increases
wave height and steepness and shortens the wavelength.
- The part of the wave in the deeper water moves faster, causing the wave to bend.
- Overall effect - wave energy is concentrated on the headland, causing greater erosion.
- The lower energy waves spill onto the bay depositing material.
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