3.1.3.3 Costal Landscape Development

Cliff formation

Erosion concentrated at high tide line, wave cut notch forms and the overhang collapses due to gravity, retreats to from wave cut platform which extends many metres and reduces erosion

Wave cut notch

Undercutting at high energy zone

Factors affecting cliff profile and retreat rate

Lithology, structure, wave energy, sub aerial processes, costal morphology

How does lithology affect cliff profile and retreat rate (with examples)

Clay causes rapid retreat (Holderness ½ metre a year) and Granite slow retreat (Cornwall retreats 1mm/year)

How does structure of the rock affect cliff profile and retreat rate

Joints/bedding planes increase erosion and concordant/discordant coastlines impactful

How does costal morphology affect cliff profile and retreat rate

Beach presence reduces erosion and headlands receive wave energy from refraction

Formation conditions for a beach

Constructive waves, low energy, large sediment supply

Swash aligned beaches

Low energy environments that is parallel to waves

Drift aligned beaches

Form where waves approach at an angle and cause longshore drift

Zonation of beaches

Backshore, Foreshore, Nearshore

Backshore

Located above high tide, only changes in major events

Foreshore

Area between high/low tide where active processes occur

Nearshore

Underwater section acts as a transition zone from ocean to land

Distinctive beach features

Storm ridges, berms, cusps

Storm ridges

At the backshore consisting of large material from a strong swash

Berms

Smaller ridges marking successive high tides from constructive waves

Cusps

Crescent shape indentation on mixed sand which concentrates swash energy and creates backwash that removes sediment that maintains feature

Formation and development of a beach

Positive sediment budget to from depositional landform between high/low tide. Constructive waves build up in summer and destructive removes in winter to create negative feedback loop. Reference backshore, nearshore, foreshore. Reference distinctive beach features. Angular material found at the top of the beach, drift aligned allow transport but swash aligned don’t

Spits, process and example

Longshore drift moves sediment into the sea/across a river mouth on a drift aligned beach after the coastline changes shape. The outward flow of the river prevents formation across an estuary, with wave refraction carrying material to sheltered water behind the tips (recurved tips). E.g Spurn head

Compound spit

Formation of barbs indicate changing wind direction

Tombolo, formation and example

Sand/shingle bar connecting an island to the mainland and acts as a sediment sink. Wave refraction cause low velocity/energy waves to deposit sediment landward. e.g Lindisfarne

Offshore bars and formation

Submerged ridges of sand running parallel to the coastline. Form due to energy dissipation nearshore and backwash from destructive waves removes sediment. Acts as negative feedback by breaking waves early to prevent future erosion

Barrier beaches and formation

Beach/spit extends across a bay to join headlands. Rising sea levels from glacial melt push sediment inland, leaves trapped water called a lagoon. Occurs in low tidal range, constructive environments with consistent sediment supply

What is required for sand dunes to form

Large sediment supply, Onshore winds, Vegetation colonisation

Order of sand dunes

Embryo, Fore, Yellow, Grey, Dune slack, Climax vegetation

Pioneer species

First colonising plants with adaptions to survive (e.g sea rocket) which then bind to sand (e.g Marram grass) and form fore dunes

Formation conditions for mudflats/saltmarshes

Sheltered/low energy land, fine sediment supply, salt and fresh water meet

Development process of salt marshes

Fine sediment deposited at low energy environments by flocculation at high tide line. Pioneer plants (like eelgrass) further trap sediment which allows the salt marsh to rise above the high tide and form a meadow. The environment eventually becomes hospitable and causes climatic climax

Flocculation

Particles clumping together until they sink

Causes of sea level change

Eustatic, Isostatic, Tectonic activity

Eustatic change

Global change where sea levels rise/fall from melting/thermal expansion

Isostatic change (with Scotland and SE England example)

Local change where land recovers from weight in subsidence. Scotland rises 1mm/year whereas SE England sinks 1mm/year from sediment weight in the English Channel

Emergent landforms

Land rises/sea falls to create landforms like raised beaches

Raised beach development

Emergent landforms driven by isostatic recovery, for example Jura. Flat areas with vegetation succession due to lack of wave action, fossil cliffs found at backshore

Submergent landforms defintion

Flooding in coastline as sea levels rise

Submergent landforms example

Rias, Fjords, Dalmatian coasts

Rias and formation

Submergent landforms formed when eustatic sea level rises. Flooded and winding V - shaped valleys that decrease in depth further inland. Dartmouth, Devon

Fjords

Submergent landforms from eustatic sea level change. Flooded U shaped glacial valleys which are deeper in the middle with steep banks than at threshold. West Coast Norway

Dalmatian coasts

Submergent landforms. Form when eustatic sea change at concordant coastlines flood valleys running parallel to the coast. Create long/narrow/rugged islands. For example Croatia

Cove formation

Hydraulic action exploits faults in concordant coastline rock. The sea erodes the soft rock rapidly to create a wide bay, wave refraction erodes in all directions. Erosion stops when it reaches next band of hard rock.

Lagoon formation

Longshore drift extends a spit until it becomes a bar. This cuts off water supply to create low energy environment and remaining body becomes brackish and a lagoon (salt marsh in the future)

Recent and predicted climatic change and potential impact on coasts.

Inundation/Submergence (10%+ of Bangladesh >1 metre above sea level), Accelerated backshore coastal erosion, Salinisation, Loss of natural depositional buffers through storm surges