Durlston Bay / Studland Bay / Poole Harbour / Poole Bay / Christchurch Harbour / Christchurch Bay / Hurst Spit / Swanage Bay
Christchurch Bay (CBY)
Hengistbury Long Groyne to Hurst Spit
Christchurch Bay comprises a 16km section of open coastline exposed to dominant waves from the south-west. The beaches are generally comprised of finer beach material on the more sheltered western side of the Bay, with coarser beaches further to the east.
The coast has been formed and is characterised by cliff geology and continual erosion (at a historic rate of approximately 1m per year).
Over the past century, however, coast protection works have been implemented to protect areas of development and these have contributed to the form of the coast, in particular the Long Groyne and the 17 associated groynes sited due north of it at Hengistbury Head.
Barton fares particularly badly and work over recent years includes construction of a new revetment, rock groynes and cliff drainage works. Barton golf course has had to expand landwards to replace areas lost to the sea - a move that is encouraged here and wherever the land at risk of erosion does not warrant major expenditure on coast protection works.
Mudeford Sandbank which lies in the lee of Hengistbury Head suffered considerable loss of beach material, particularly since construction of the Long Groyne in 1938, leading to the threat of a breach to Christchurch Harbour. Such a breach would lead to increased flooding of land and property around the harbour and the Council developed a scheme to improve the standard of defences along the seaward edge the sandbank (picture left).
Soft eroding cliffs fronting Naish Holiday Village near New Milton are designated a geological SSSI and are unprotected for that reason, but there is increasing need for measures to reduce erosion and improve the aesthetics of the beach.
The steady decline in the volume of beach material at the foot of local cliffs since the early 1900's has been blamed on the construction of coast protection measures in Poole Bay. Research in the 1970's, however, found evidence that beach renourishment carried out in Poole Bay has become a source of sediment supply to Christchurch Bay. Christchurch Borough Council have taken advantage of this by constructing rock groynes on beaches east of the harbour entrance, part of an extensive 25 year programme of coastal works that was completed in 2000. The SMP review process will aim to provide strategic guidance for those areas that may still need addressing.
In SMP1 the shoreline of Christchurch Bay is divided into 7 Management Units:
Hengistbury Long Groyne to the tip of Mudeford Spit
Mudeford Spit to Chewton Bunny (incl. Mudeford Quay)
Chewton Bunny to start of defence at Barton-on-Sea
Start of defence to Beckton Bunny Outfall
Beckton Bunny Outfall to Hordle Cliff
Hordle Cliff to Hurst Spit
Bournemouth Borough Council, Christchurch Borough Council and New Forest District Council
Christchurch Coast Protection Facts:
Christchurch Borough Council administers 10.3km of coast including a considerable length inside Christchurch Harbour. On the coast outside the harbour, there are 50 groynes, 4km of sea wall, 2km of vulnerable cliffs and 3ha of special salt-tolerant grass sward. The 1990 value of these defences was estimated at £8m and they protect, conservatively, about £100 million of real estate in the front line.
From: Coast Protection in Christchurch
Year 11 – this is the booklet for your controlled assessment fieldwork to Hengistbury Head. Remember the booklet is for the fieldwork day and is to be completed in detail for you to refer back to when you complete the rest of the project.
Bear in mind the overall title at all times: To what extent is geology the main influence on the distinctive coastal landforms of Hengistbury Head and Mudeford Spit?
This needs to be broken down.
Firstly, you need to identify what the distinctive (unique, unusual) landforms are first, e.g. the spit is distinctive compared to other areas within a 50mile radius, the headland is distinctive because of its history, the marsh is distinctive because it is a SSSI (Site of Special Scientific Interest) and has a protected species.
Then consider what ALL the possible influences are on the landforms: geology, human influence (coastal management and the nature reserves), geomorphic processes (erosion, deposition, transportation). Try to weigh up and predict which factor you think will be most influential on changing the landforms.
You can argue the case that geology IS the main influence, or is NOT. So long as you can PROVE IT by collecting data / evidence on the trip and in your research. Your evidence must be analysed and explored using theory (e.g. link longshore drift to the type of geology, link the creation of the salt marsh to the presence of groynes, etc.).
Remember: fact, theory, evidence. Analyse, explain, suggest.
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