Case study: Keyhaven marshes Flashcards
Their development was linked to…
The formation and subsequent migration of Hurst Castle Spit
How long is the spit?
The spit extends some 4 kilometres across the Solent and provides a sheltered environment in which the mud flats and marshes have formed
The current marshes owe much to the vitality to what?
Spartina anglica since the nineteenth-century. This has enabled these marshes to grow some two metres higher than might otherwise have been the case.
What caused the loss of shingle supplied by longshore drift?
Partly by groynes and other engineering works to the west
The recession of the spit over the marshes has had two effects…
Firstly, the marsh has subsided under the weight of the shingle. This has reduced the height of the spit.
Secondly, the marsh has become exposed on the seaward side of the spit. This has led to its rapid erosion.
This combined with other factors - reduced shingle supply and increased storm events - has led to breaches in the spit itself.
he Spartina marshes themselves have been in decline since the 1950s. The resultant die-back has…
Exposed slumping platforms of bare mud (very vulnerable to marine erosion).
Releases of mud could affect the stability of the spit, clog navigation channels and destroy the marsh ecology.
As well as reducing the primary productivity of the area it would have a knock-on effect on the invertebrates and eventually the bird life of the western Solent.
It is not surprising, therefore, that the area is protected under a number of designations.
These include its status as a Site of Special Scientific Interest (SSSI) and as a wetlands RAMSAR site covered under European law.
The shoreline management plan (SMP) published in 1998 evaluated the options for protecting the marshes.
It noted that their survival was dependent also on the survival of Hurst Castle Spit.
550 metres of rock armour.
Armoured breakwater.
Nourished with 300,000 cubic metres of shingle.
100-metre rock revetment was built at the eastern end of the spit to protect its tip or distal end.
