Case Study: Christchurch Bay - PowerPoint Presentation

Slide1

Case Study: Christchurch Bay

An extended stretch of coast.Slide2

Overview to Christchurch Bay

Christchurch bay is located on the South Coast of England. It is formed between the headland-

H

egistbury Head near Christchurch, Dorset and a spit at Hurst,

Keyhaven close to the town of Lymington in Hampshire.

Christchurch bay is located within cell 5 of the England and wales sediment cells however this stretch of coast acts as a sub cell on its own with little sediment leaving this area and coming into the area.

Christchurch Bay comprises a 16km section of open coastline exposed to dominant waves from the south-west.

This area of coast erodes at between 1-3m/ year Slide3

Geology

The rocks and clays forming the Christchurch Bay and Solent coasts include

materials laid down when the Solent was an estuarine river that drained the

Hampshire Basin. These were never subjected to the great pressures that formedthe harder rocks to the west. With rising sea levels after the last Ice Age, thechalk ridge that formerly linked the Purbecks with the Isle of Wight wasbreached, and the former river valley became the new coast, and started toerode. This led to the formation of Poole Bay. The land to the east was protectedinitially by the ironstone outcrop at

Hengistbury Head, but in due course this tooeroded and, as sea levels continued to rise, Christchurch Bay began to develop.The dominant south-westerly wind and waves created a littoral drift of shingleand sand along the coast in an easterly direction, initially forming the ShinglesBank which lies between the mainland and the Isle of Wight, and subsequentlyforming Hurst Spit. Slide4

Fetch

Wind action generates waves that impinge on the shore from various directions.

The longer its ‘fetch’ (the distance the wind travels without interruption),

The more powerful are the waves that it generates. Around the District’s coast, winds are strongest in Christchurch Bay, where the fetch varies from 10 km for winds from the north to many thousands of kilometres for those from the

south-west, extending across the Atlantic Ocean to the coast of South America. Slide5

Sediment Cell 5

LSD

wind

INPUTSlide6

WEST TO EAST

Hegistbury Head

Mudeford Quay

Mudeford/Avon Beach Site 1 Highcliffe Cliffs site 2 Barton on sea site 3 Milford on sea Site 4Hurst spit site 5 Slide7

Hegistbury Head

Hegistbury

Head is a sandstone headland

located in Dorset on the south coast close to Christchurch between Southampton and Bournemouth. HH is a SSSI

The headland on the west side of the bay.

The groyne that sticks out into the sea makes sure that sediment from Bournemouth bay doesn’t spread into that of Christchurch bay. Slide8

Mudeford Quay

Mudeford is where the Avon and Stour flow out of Christchurch harbour into the sea this flow stops Hegistbury head connecting with

M

udeford spit.

Hegistbury Head

Mudeford Spit

Mudeford Christchurch Harbour Slide9

Mudeford/ Avon Beach Site 1

Avon beach is located to the east of the quay. This is one of the sandiest beaches in the bay . This is due to the coastal defences in the area but also due to artificial dredging.

Sea wall

embankment

groyne

Mudeford quay

Mudeford spit

Avon beachSlide10

Highcliffe site 2

Highcliffe castle beach

Friars cliff

Site 2

LSD takes away material from these beaches. And takes it to Hurst

The HH long

groyne

stops these beaches looking like those at Bournemouth. As less sediment is transferred to this bay. Slide11

Highcliffe site 2A

In this picture you can make out the coastal slump due to the recent bad weather.

N

aish

holiday village sits on top of this cliff. The cliff is retreating at roughly 1m per year.

To Barton

TO HHSlide12

Barton-on-sea Site 3

Barton beach 

-Coastal

management:

Groynes, Rock armour, 

Each stone costs roughly £5000- Erosion toward the middle of this picture you can see mass movement at Barton- rotational slip - this is due to cliff collapse due to a permeable rock sitting on an impermeable rockSlide13

Milford On Sea Site 4

Milford - sea wall rock armour

Cliff

is very close to sea this is eroding very quickly up to 3m per yearrocks have been moved by current stormsThe fetch here comes all the way from

Brazil, this coast gets battered by storms.Slide14

Hurst Spit site 5

Currently there is Less

material

than usual at the spit is due to the recent storms.Therefore emergency work is in place to rebuild the spitwithout this spit Lymington and surrounding area would be under water!Hurst spit it the headland at the most eastern part of the bay. Hurst spit is formed due to a change in direction on the coast and a river mouth, this creates the spit with Hurst castle on the end of it and Keyhaven salt marshes.Slide15

Case study – Erosion and Destruction

JAN/FEB storm 2014

Highcliffe

Avon Beach

Hegistbury Head

Mudeford

Barton

Milford – marine restauran

t

Hurst Spit

Milford Beach hutsSlide16
Slide17

Sources

Ian West - Southampton University

New Milton Advertiser

Google Maps