What did Dunwich used to be like? Right on the Eastern coast it was once a thriving port, similar in size to London but storms, erosion and floods have almost wiped out this once prosperous village which was the capital of East Anglia. All that now remains are a few cottages where once there was six churches, three chapels, two monasteries and even a mint. It's rumoured that most of it is under the sea and on a quiet day it's said you can hear the church bells of the doomed village still ringing out ... What Dunwich might have looked like…
Coastal Erosion at Dunwich… Why are the cliffs at Dunwich easily eroded? <ul><li>They are made up of soft sands and gravels… </li></ul><ul><li>made worse by the narrow beach </li></ul><ul><li>as well as erosion by the waves at the base of the cliffs, they are also attacked by weathering! </li></ul>When does the most erosion occur at Dunwich? Why is this? <ul><li>Most erosion occurs during storms (due to high energy destructive waves) </li></ul><ul><li>At high tide – when waves are able to pound at the base of the cliffs. </li></ul>
Rates of erosion at Dunwich are now as great as one metre per year! Actively eroding cliffs – absence of vegetation shows that erosion is recent The line of pebbles show the high tide mark on the cliff Source of Photos: http://www.stacey.peak-media.co.uk/DunwichHeath/DunwichApril2005/DunwichApr2005.htm
This photo clearly shows two levels at which the base of the cliffs has been eroded at high tide! Photo Source:http://www.stacey.peak-media.co.uk/DunwichHeath/DunwichApril2005/800-P1010829.JPG
What is Longshore Drift? The large scale movement of material along the coast
In what direction does material move along the coast at Dunwich? Mark on the prevailing wind direction and draw on the pattern of longshore drift along the coast at Dunwich. Question – Get thinking! How does longshore drift contribute to the erosion problem at Dunwich?
Is there any coastal management at Dunwich today? <ul><li>Why do you think this is? </li></ul>
<ul><li>REMEMBER </li></ul><ul><li>Dunwich is an excellent example of coastal erosion to use in answering exam questions. </li></ul><ul><li>You must make sure you learn: </li></ul><ul><li>The location of Dunwich </li></ul><ul><li>What the erosion problem is (e.g. amount of erosion / year) </li></ul><ul><li>The reasons for the rapid erosion at Dunwich </li></ul><ul><li>What has been lost at Dunwich as a result of the erosion </li></ul><ul><li>Why little is done to prevent erosion at Dunwich </li></ul>So is Dunwich Doomed?
A Case Study of Coastal Management: Aldeburgh, Suffolk <ul><li>Action at Aldeburgh </li></ul>
Action at Aldeburgh <ul><li>Background: </li></ul><ul><li>Aldeburgh is a little further south from Dunwich on the Suffolk Coast – like Dunwich it has been affected by coastal erosion but here more has been done to protect the coastline! </li></ul><ul><li>Why has action been taken at Aldeburgh to protect the coastline but not at Dunwich? </li></ul>
COASTAL MANAGEMENT WHAT ARE THE OPTIONS? HARD ENGINEERING SOFT ENGINEERING Coastal Defence Structures (man-made, which reflect large amounts of wave energy. Beaches or naturally formed materials used to control / re-direct erosion processes
2. RIP-RAP (Rock Armour) Advantages? Disadvantages? rip rap is simply boulders/stones the waves break on the rip rap and not on the coastline
3. GROYNES Advantages? Disadvantages? These stop Longshore drift trapping the sand and shingle and building up the beach to create a natural coastal defense against the waves which break on the beach rather than against the cliff.
4. GABIONS Advantages? Disadvantages? Although not used at Aldeburgh there are 2 other types of hard coastal defence:
7. BEACHES / SALT MARSHES A wide beach or salt marsh area will help to absorb wave energy before it is able to attack the cliff line, helping to reduce erosion Advantages? Disadvantages?
So what is the Action at Aldeburgh? <ul><li>REMEMBER </li></ul><ul><li>Aldeburgh is an excellent example of coastal management to use in answering questions. </li></ul><ul><li>Make sure you learn: </li></ul><ul><li>Why action has been taken at Aldeburgh and not at Dunwich? </li></ul><ul><li>What types of action have been taken, how they work and their advantages and disadvantages </li></ul><ul><li>Is the protection worthwhile? </li></ul>