Spits – Spurn Head & Orford Ness
Aided by rapid input from glacial material
Little or no refraction from F.H.
Proximal retreat in balance with the
Humber channel “forced” south
• Single spit
• 15km long - vegetated
• Diversion of R. Alde
• Dynamic growth:
• 64m p.a. 1962 to 1967
• 183m p.a. 1804 to 1812
• 2.9km 1812 to 1821
Sheltered sedimentation zone
Distal needs ↑ sediment as it
reaches across deeper water
Poole Harbour Christchurch Harbour
1785 channel outflow 1880 spit extenison from
through “Little Sea” south to north almost to
By 1875 entrance migrated
Managed to maintain channel 1886 & 1935 spit breach by
Migration due to off shore
bar inshore migrating
Northern spit is remnant
PH = swash aligned, CH = drift aligned
Created during the Flandrian Transgression
Relic feature – positive eustatic change
Ley fed by three streams, shallow lake –
usually higher than sea level
Bar beach easily breached – 2001 – normal
conditions; 4m tidal range, 0.5m wave
height (storm up to to 2m)
Future impact of eustatic change?
Composition – flint pebbles – provenance 30/40km
@10k BP offshore barrier moved onshore by “roll
@5 k BP Intermediate step of forming barrier
@3k BP emergent coastline created headland
divisions of Start Bay
Dynamic equilibrium –
local sea level rise = 2-4mm p.a.
evidence from current storm roll over = 0.5m
p.a. inward migration
LSD north and south in equilibrium
over centuries if not smaller scales
Short term storm:
Roll over crest & remove forebeach
Forebeach rebuilt over time.
↑ storms → reduced barrier
Swash aligned beaches ; Drift aligned beaches;
Some beaches show oblique
·Smoothly curving concave alignments to the dominant wave
· Beach face is orientated parallel Usually occurs where the beach
to the fronts of the dominant gradient is steep and the wavelength
waves. is short.
· Beaches which face the waves This is because the crest breaks at
are termed swash aligned. different times along the beach.
Spits; Spits II;
e.g. Spurn Head, Holderness, As spits build further in to deeper Barrier beaches
Yorkshire. water, they require more sediment to Beach which stretches across from
Dominant waves push material along build above the HWM. The waves one embayment to the other, and
the coast in longshore drift. Coast have greater energy to attack the encloses a lagoon behind it
turns inwards, and the material distal end, turning it inwards. , e.g. Slapton sands, Cornwall.
continues to be deposited in line with Sometimes, the curves are due to the Feature is swash aligned, and has
the coastal trend. Finer materials are changing of the predominant wind probably been driven landwards
deposited in the sheltered side of the direction to another, causing from the offshore zone.
spit. Marshes can build up, and this waves, and thus deposition to occur
forces the river to the other side of the an a different angle. These recurves
estuary. are sheltered by the spit and become
prominent features, e.g. Hurst Castle
Spit, The Solent.