coasts

Discordant Coast

East Dorset (Old Harry Rocks)

- Alternating bands of hard chalk and soft clay run perpendicular to the coast

- Softer rock erodes faster → forms bays, harder chalk remains as headlands

- Old Harry Rocks = chalk stacks formed by hydraulic action + abrasion

- Originally part of a headland → erosion created caves → arches → stacks

- Located on the Jurassic Coast (UNESCO site)

Concordant Coast

Lulworth Cove (Dorset)

- Rock layers run parallel to coastline

- Outer layer = hard limestone, inner = soft clay

- Waves break through weak point → rapid erosion of softer rock behind

- Creates circular cove shape due to even erosion

- Narrow entrance = resistant limestone still protects coastline

Concordant Coast

Dalmatian Coast (Croatia)

- Formed by submergence of parallel ridges (anticlines)

- Sea level rise flooded valleys → left long narrow islands

- Coastline runs parallel to geological structure

- Calm, sheltered waters → low wave energy environment

- Important for tourism → shows economic value of coastal landforms

Haff Coast – Baltic Sea

- Low-energy coastline → dominated by deposition

- Longshore drift creates sand spits/bars

- Lagoons trapped behind bars = haffs

- Found in Germany/Poland Baltic coast

- Shows how deposition > erosion shapes coastline

Spit – Spurn Point (Holderness)

- Formed by longshore drift moving south

- Sediment deposited where coastline bends at Humber Estuary

- Spit is ~5.5 km long

- Hooked end due to changing wind/wave direction

- Dynamic feature → often breached during storms

Mass Movement – Holderness

- Dominated by boulder clay (glacial till) → weak and unstable

- Saturation from rainfall → increases slumping risk

- Marine erosion undercuts cliffs → triggers collapse

- Retreat rate ≈ 1–2 m per year (fastest in Europe)

- Major contributor to rapid coastal retreat

Rotational Slumping

Holbeck Hall (1993)

- Heavy rainfall → saturated cliff material

- Rotational slip caused hotel collapse

- ~70,000 tonnes of earth moved

- Cost ≈ £1.5–2 million damage

- Example of mass movement not in Holderness

Sediment Cell

Flamborough Head to The Wash

- Self-contained sediment system

- Flamborough Head = sediment source

- Holderness = erosion supplying sediment

- Spurn Head = deposition zone

- Human interference disrupts sediment flow

Holderness

Rapid Coastal Recession

- Located East Yorkshire, faces North Sea

- Boulder clay geology → easily eroded

- Strong destructive waves + long fetch

- Longshore drift moves sediment south

- ~2 m/year erosion, up to 10 m in storms

Emergent Coast – Scotland

- Isostatic rebound → land rising

- Former sea beds exposed

- Raised beaches + fossil cliffs

- Relative sea level fall

- Shows post-glacial adjustment

Submergent Coast – South England

- Land sinking → relative sea level rise

- River valleys flooded → rias- Irregular coastline forms

- Example: Dartmouth

- Shows drowning of coastline

Dalmatian Coast (Submergent)

- Parallel ridges submerged

- Long narrow islands formed

- Coastline runs parallel to structure

- Calm waters

- Tourism importance

Nile Delta

- Located in Egypt

- Reduced sediment due to Aswan Dam

- Increased erosion + subsidence

- Sea level rise threatens farmland

- ~40 million people depend on delta

Kiribati

- 33 atolls in Pacific Ocean

- Avg height ≈ 2 m above sea level

- Sea level rising ≈ 3–4 mm/year

- Saltwater damages crops + water

- Planned relocation strategy

Bangladesh - Cyclones & Storm Surges

Cyclone Aila (2009)

- 80% of Bangladesh is less than 5m above sea level

- Cyclone Aila produced 3-4m storm surges

- Poorly maintained embarkments were breached by 3-4m storm surges

- 3.9 million affected, 190 dead, 7100 injured

- ~ US$270 million damage caused

- 350,000 acres of cropland damaged

Bangladesh - Subsidence

- Bangladesh is a delta made from thick layers of sediment

- Parts of the coast are experiencing subsidence

- As the land sinks, and sea levels rise, Bangladesh becomes more at risk to coastal flooding and storm surges

UK (1953) - Storm Surges

East Coast - North Sea

- Severe low pressure system + strong winds + high spring tide = Storm Surge

- East Coast is low-lying and poorly maintained

- 307 dead, 32,0000 homes damaged

- Saltwater flooded farmland: soil contamination, damaged crops

- Emergency rescue and evacuation carried out

UK (2013) - Storm Surges

East Coast - North Sea

- Low pressure system + strong winds = Storm Surge

- High tide and increased water levels → pressure on defences

- 1400 homes flooded, thousands evacuated (warnings given prior)

- Damage to homes, businesses, roads, and coastal infrastructure

- Seawater flooded farmland - salinisation

- Services carried out evacuation and rescue

Conflict

Skipsea, Holderness Coast

- Erosion rates are 1.4m/per on avg

- People feel nothing is being done to protect their village (pop of 700)

- Money is being spent on coastal defences in neighbouring towns/villages

- Decision was a result of a Cost-Benefit Analysis

Hard Engineering

Mappleton, Holderness Coast

- Has 2 rock groynes and rock armour

- Built to protect the village and main road

- Erosion rates fell from ~ 7-10m/yr to ~ 1-2m/yr

Soft Engineering

Hornsea, Holderness Coast

- Beach replenishment: adds sediment → replaces lost material from LSD → creates a wider beach

- Limitation: Expensive, needs constant management- LSD can remove sediment

Winners & Losers

Mappleton & Cowden, Holderness Coast

- Winner: Mappleton — 2 groynes + rock armour → erosion fell from ~7-10m/yr to ~1-2m/yr

- Loser: Cowden — TGS - starved of sediment → erosion rose from ~1m/yr to 3-4m/yr

Sustainable Management

Medmerry Managed Realignment

- Old shingle defence deliberately breached

- New 7km flood embarkment built further inland

- Allowed sea to flood the land b/t new and old defences

- Created saltmarsh and mudflats, naturally protect 348 properties and infrastructure