Isle of Purbeck - Sea level change and coastal systems Flashcards
Where is Durdledoor?
Durdledoor is part of the jurrassic coast in southern england, Dorset.
What processes affect chichester harbour?
erosion - abrasion, attrition, hydraulic action, corrosion (solution), wave pounding, wave quarrying, caultation.
Transportation
Where is Chichester harbour?
It is an area a site of specific scientific interest (SSSI). It consists of an area that is 31km2 of mudflats, salt marshes, spits and deep mud banks.
When was Chichester habour formed?
The natural harbour was formed when part of an ancient river system was indundated by the post-glacial rise in sea level.
How is chichester harbour a system?
What are the inputs for Chichester harbour?
Energy inputs include- winds, waves, tides and sunlight, offshore sediment, fluvial sediment, basin and edge and estuary sediment, beach recharge, sea grass and saltmarsh plants,
Which winds is the coast protected from?
The coast is protected from south westerly prevailings winds and waves by the isle of wight but is exposed to southerly gales especially in winter, and these can create high waves.
How does the shape of the harbours entrance protect it from sea waves?
The entrance to the harbour is narrow which protects from sea waves penetrating too far in to the basin, creating a low energy environment.
What limits the power of the local waves?
The local waves are created by wind blowing across the water surface inside the harbour, also have limited power because of the restricted fetch.
What are some inputs for sediment and nutrients?
Sediment and nutrients inputs are derived from several sources. Waves and currents erode material from the floor of the solent, which is carried into the harbour by the incoming flood tide.
How do waves at chichester harbour contribute to the system?
Input - waves
Processes - erosion
Outputs - silt and clay
Stores - saltmarshes
How do tides at chichester harbour contribute to the system?
Input - tides
Process - transport
Output - sand
Stores - mudflats
How do currents at chichester harbour contribute to the system?
Input - currents
Process -deposition
Output - Organic matter
Stores - sand banks
How does sunshine at chichester harbour contribute to the system?
Input - Sunshine
Process - sedimentation
Outputs - tides
Stores - sand and gravel beaches
What is accretion?
Growth in height of the land owing to accumulation of sediment.
What is coastal squeeze?
Loss in intertidal habitat which occurs when the high water mark
What feature at Chichester harbour is an example of a feature that has changed due to natural and human influences?
East head spit.
Why is understanding the function of the system important for successful management of the harbour?
It means that because the area is an SSSI for birds
what are some limiting factors for sediment and nutrient input?
Yeilds of sediment are low despite the rock being relativley easy to erode (gravel, sands and clays) because the local waves have limited energy. The coastal bluffs are also low in height which limits the amount of sediment available for wave erosion like attrition and abrasion.
What kind of coastal management strategies have been put in place at Chichester harbour?
90% of Chichester harbour is protected by hard engineeering strategies like sea walls, rock armour, gabions and earth embankments, which all reduce rates of erosion.
What are some limiting factors of smaller sediment inputs such as sand and gravel?
This input is transported westwards by longshore currents and is in limited supply by the coastal defences.
What is East head spit?
It is a single spit that flanks the entrance to chichester harbour, it is topped with sand dunes and its about 1km in length. its southern end is known as a hinge is only 25m wide and it broadens out to the north to about 400m.
What is the name for the area of land that lies between the channel entrance?
Between the main channel entrance and and the spit is The winner which is an area of sand and gravel. Behind the spit is a saltmarsh and mudflats.
How did the spit grow before 1870?
It grew westwards, supplied by shingle and sand eroded from cliffs and beaches near Selsey and carried west by longshore currents. The drift is westwards here (contrary to much of the south coast ). This is because the isle f wight acts as a waterbreaker, causing prevailing southwesterly waves to refract and diffract to more southeasterly approach.
