View stunning SlideShares in full-screen with the new iOS app!Introducing SlideShare for AndroidExplore all your favorite topics in the SlideShare appGet the SlideShare app to Save for Later — even offline
View stunning SlideShares in full-screen with the new Android app!View stunning SlideShares in full-screen with the new iOS app!
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?
They are made up of soft sands and gravels…
made worse by the narrow beach
as well as erosion by the waves at the base of the cliffs, they are also attacked by weathering!
When does the most erosion occur at Dunwich? Why is this?
Most erosion occurs during storms (due to high energy destructive waves)
At high tide – when waves are able to pound at the base of the cliffs.
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?
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
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
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.
4. GABIONS Advantages? Disadvantages? Although not used at Aldeburgh there are 2 other types of hard coastal defence: