1. A Case Study of Coastal Erosion: Dunwich, Suffolk <ul><li>Is Dunwich Doomed? </li></ul>
2. Where is Dunwich?
3. 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…
4. 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>
5. 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
6. 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
7. What is Longshore Drift? The large scale movement of material along the coast
8. 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?
9. Is there any coastal management at Dunwich today? <ul><li>Why do you think this is? </li></ul>
10. <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?
11. A Case Study of Coastal Management: Aldeburgh, Suffolk <ul><li>Action at Aldeburgh </li></ul>
12. 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>
13. COASTAL MANAGEMENT WHY IS IT NEEDED?
14. 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
17. 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
18. 3. GROYNES Advantages? Disadvantages?
19. How do groynes work? Groynes trap the sand which is carried along the coast by longshore drift . The sand acts as a natural protection against the force of the waves. The waves break on the beach and not the cliffs. Source: BOARDWORKS
20. Decision making exercise Seaview 0 10m Engleton Prevailing wind buildings groynes till Roman Palace N Why is Seaview being eroded? Should Seaview be protected from coastal erosion? If so, how? Source: BOARDWORKS This is the imaginary coastal town of ‘Seaview’. Seaview has been suffering from coastal erosion for the last 15 years since the nearby larger town of ‘Engleton’ had groynes built to protect its own coastline. Seaview is built on ‘till’ (soft clay) and is losing up to 30cm of land per year. Why protect Seaview? The town is home to 20,000 residents. The remains of a Roman Palace are located here. This attracts tourists.
21. 4. GABIONS Advantages? Disadvantages? Although not used at Aldeburgh there are 2 other types of hard coastal defence:
22. 5. REVETMENTS Advantages? Disadvantages?
23. Option 2 SOFT ENGINEERING Beach Nourishment Salt Marshes
25. 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?
26. 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>