Beaches:
Formed by the accumulation of material deposited between high and low tides. As sediment
size increases so does beach angle.
Storm beach – Storm waves hurl pebbles to back of beach.
Berms – Smaller ridges that develop at high tide mark.
Cusps – Small, semi-circular depressions. Temporary features formed by waves reaching the
same point when swash and backwash have similar strength.
Ripples – smaller, less developed sand dunes.
Ridges – Develop parallel to the shore as material is carried back down the beach.
Occasionally breached by channels draining water off the beach.
Spits:
Long, narrow beaches of sand/shingle that are attached to land at one end and extend
across a bay, estuary or indentation in a coastline.
• Longshore drift in 1 dominant direction carries sediment to the end of the beach and
into open water.
• End of spit curves due to wave refraction/secondary wind.
• Estuaries can limit development due to river currents.
• In the sheltered area behind a spit, deposition occurs as wave energy is reduced.
• Silt and mud deposited build up and eventually salt-tolerant vegetation colonises as
a salt marsh.
E.g = Spurn Point spit, Holderness
4.8km long, low energy Humber estuary, marsh behind (may develop into sand dunes).
Onshore Bars:
Develop if a spit continues to grow across an indentation in coastline until it joins onto the
land at the other end, forming a lagoon.
E.g = Slapton Sands, Devon
100m wide bar, but due to no significant longshore drift it’s now thought to have formed by
onshore movement in post-glacial sea level rise (6000 years ago).
Tombolos:
Beaches that connect the mainland to an offshore island, often formed from spit extension.
E.g = Chesil Beach, Dorset
30km long, onshore shingle migration (6000 years ago) produced uniform sediment
distribution which was pushed east by longshore drift.
Salt Marshes:
Vegetated areas of deposited silt and clays in low-energy environments.
• Fresh and salt water neutralise negative charge and clay flocculates.
• Sea shore with little wave action allows particles to fall out of suspension.
• Sediment source via rivers/the sea.
• Continual deposition of sediment enables mudflat formation.
• Salt tolerant pioneer plants (halophytes) colonise and their roots stabilise mud –
eelgrass
• Vegetation increases friction and further deposition.
• Land rises above tidal level and is exposed at low tide, enabling further species to
colonise- glasswort and sea lavender.
• Decomposition adds nutrients, allowing succession to continue above sea level as
salinity levels fall and soil develops- seablight.
• Eventually salt marsh is zoned by tidal levels to create the climax community.
Deltas:
Large areas of sediment found at the mouths of many rivers.
• Rivers entering sea carrying large sediment load.
• Broad continental shelf at river mouth allows sediment to be deposited in lowenergy environments with low tidal ranges.
• Distributaries form when the river is overloaded with sediment and deposition in the
channel forms bars which split the channel in 2.
• Reduced energy in 2 channels increases deposition and further dividing.
• Levees along banks may line channels but flooding breaches these and deposits
occur in low-lying areas between levees called crevasse splays.
Upper delta plain= inland beyond tides, river sediment.
Lower delta plain= Inter-tidal zone, river and marine deposits.
Submerged plain= lies below mean water mark, marine sediment.
Cuspate= Pointed extension to coastline, occurs when sediment accumulates but is shaped
by regular, gentle currents from opposite directions.
Arcuate= Sufficient sediment supply available for delta to grow seawards, but wave action is
strong enough to smooth and trim leading edge.
Bird’s foot= Distributaries out from coast in a branching pattern, river sediment supply
exceeds removal rate by waves and currents.
Case Study- The Nile Delta
Low energy coastal environment
Location =
Egypt, South of Mediterranean and West of Red Sea.
Prevailing north-westerly winds and sediment movement east.
Short fetch; lower wave energy enables accretion
The River Nile =
Sediment yield of 4.26 t/ha/yr
Catchment of 3 million sq km
Human Impacts on sediment budget =
Increasing population drained and polluted river
Climate change → rising Mediterranean Sea levels
Competition over water.
Aswan Dam (1964) disrupted erosion and accretion
Coastal retreat up to 148m/yr
Coastal/Foreshore
Plain
Frontal Plain Sandy Zone Delta Plain
• Parallel ridges
• Salt marshes
• Low energy
backshore tidal
lagoons
• Clay
deposits
• limestone
outcrops
• Sheets
• Dunes
• Hummocks
• Underwater sand bars (tideless)
• Parallel longshore bars
(longshore currents)
• Crescentic bars on beaches W of
Abu Qir (Rip currents)
• Arcuate
Case Study- Saltburn-Flamborough Head:
High energy coastal environment
Geology =
60 km Yorkshire coast
Saltburn is lias and bands of lower oolite inland, Flamborough Head is discordant chalk.
Clay 0.8m/yr, Limestone less than 0.1m/yr
Energy =
Prevailing Northerly winds move sediment South
Fetch of 1500km, Saltburn is north facing
Sediment Sources =
Sub cell 1D
Whitby sediment from the River Esk (limited by construction of weirs + reinforced banks)
Sediment driven onshore during Flandrian Transgression
Landforms =
Cliffs are vertical 20-30m, horizontally bedded sedimentary rock with overlying till lowered
by mass movement.
Shore platform at Robin Hood’s Bay is 500m wide and 1-15°, with shelves fringing the coast.
Current rates of erosion and retreat suggest formation in last 6000 yrs of predominantly
stable sea level.
Headland at Flamborough Head and bay at Selwicks Bay.
Over 50 geos along coastline, blowholes where vertical master joints enlarged
High energy means fast erosion and few beaches. One at Scarborough Bay
Landform Changes =
Varies form gradual erosion (rapid due to high energy) to sudden cliff collapse.
Slower landform changes occur to form depositional landforms such as spits; not found due
to high 4m tidal range and lack of estuarine environments for sediment sinks.