Coastal Systems

Coastal landscapes are dynamic, integrated, and constantly adjusting natural systems. In AQA A Level Geography, you are expected to apply systems concepts to explain how coastal processes, landforms and landscapes develop and interact over time.

This page introduces coastal landscapes as open systems, explains key system concepts, and shows how related landforms come together to form distinctive coastal environments.

1. The Coast as an Open System

Coasts operate as open systems because both energy and material move into and out of them.
They are influenced by the atmosphere, the ocean, the land, and even by biological and human activity.

Inputs of Energy and Material

Inputs drive the entire coastal system and include:

• Wave energy (generated by wind across the sea surface)
• Tidal energy (the rise and fall of the tide)
• Wind (influences waves, aeolian transport and dune formation)
• Precipitation and runoff from rivers
• Sediment inputs from:
  • cliff erosion
  • rivers
  • offshore sources
  • longshore transport from adjacent stretches of coastline

Stores / Components

Stores are the places where material is held temporarily within the system:

• Beaches and berms
• Sand dunes
• Nearshore bars
• Mudflats
• Cliffs and wave-cut platforms

Each acts as a reservoir of sediment that can shift as conditions change.

Transfers / Flows

These move sediment and energy around the coastal system:

• Longshore drift
• Wave transport (swash/backwash)
• Mass movement (rockfall, landslides, rotational slumping)
• Aeolian transport (wind-blown sand)
• Tidal currents

Outputs

Material and energy leave the system through:

• Sediment lost to deep-water deposition
• Sediment moved beyond headlands or into offshore bars
• Dissipation of wave energy
• Evaporation

Together, these components create a constantly adjusting system that seeks a balance, known as dynamic equilibrium.

2. Dynamic Equilibrium at the Coast

Coasts aim to maintain a state of balance, even though conditions (waves, storms, sediment supply, sea level) are constantly changing.

Dynamic Equilibrium Examples

• After storms, destructive waves may remove beach sediment. Calmer periods allow constructive waves to rebuild the beach.
• If sediment supply decreases, the system responds: beaches narrow, wave energy increases at the cliff foot, and erosion accelerates until a new equilibrium is reached.
• Sea-level change forces the coastline to “re-set” — new landforms develop as the system adjusts.

Dynamic equilibrium is never fixed; it is an ongoing relationship between inputs, stores, transfers, and outputs.

3. Feedback Mechanisms

Feedbacks determine whether change within the system is amplified or reduced.

Positive Feedback

Change leads to further change in the same direction.

Example:

• Cliff erosion supplies loose sediment to the shore.
• This material increases abrasion, causing more cliff erosion.
• Erosion accelerates, reinforcing the original process.
• Positive feedback can rapidly alter coastal landforms.

Negative Feedback

Change triggers processes that counteract the original change, helping re-establish equilibrium.

Example:

• Erosion lowers a beach profile.
• Sediment removed from the beach is deposited offshore, forming a bar.
• The bar forces waves to break earlier, reducing energy at the shoreline.
• This protects the beach and slows further erosion.
  Negative feedback stabilises the system.

4. Coastal Systems and Other Natural Systems

Coasts interact with atmospheric, terrestrial, fluvial, biological and tectonic systems. Changes in any one of these can alter the coastal environment.

Key Inter-system Connections

• Water cycle: Sea-level fluctuations during glacial and interglacial periods have shaped the position and nature of modern coastlines.
• Carbon cycle: Ocean acidification and climate change influence weathering processes, storm frequency and wave energy.
• Tectonic activity: Uplift or subsidence alters relative sea levels, producing emergent or submergent landscapes.
  Biological systems: Vegetation stabilises dunes and saltmarshes, shaping sediment stores.
• Human systems: Coastal defences, dredging, urbanisation and land-use changes all modify sediment pathways and energy flows.

Coasts are therefore not isolated — they sit at the intersection of multiple natural and human systems.

5. From Processes to Landforms to Landscapes

It is essential to distinguish between landforms and landscapes, and to understand how individual features combine to produce characteristic scenery.

What is a Landform?

A landform is a single physical feature shaped by coastal processes.
Examples include:

• Headlands and bays
• Wave-cut platforms
• Caves, arches, stacks and stumps
• Beaches and spits
• Sand dunes
• Saltmarshes

What is a Landscape?

A landscape is a collection of landforms and processes operating together within a particular area, shaped by geology, sea-level change and sediment transfers.

How Landforms Combine into Landscapes

Because coasts function as integrated systems, related landforms rarely occur in isolation.

Example: Headland–Bay Landscape

• Alternating bands of hard and soft rock create differential erosion.
• Wave refraction concentrates energy on headlands, carving cliffs, caves, arches and stacks.
• Lower-energy environments in bays encourage deposition, forming beaches and sometimes spits.

Example: Dune–Beach–Saltmarsh System

• Sand moved inland by wind builds embryo dunes, maturing into dune ridges.
• Behind spits or barrier beaches, sheltered areas allow saltmarshes to develop.
• The combination forms a distinctive low-energy depositional landscape.

Example: Glaciated Volcanic Coast (e.g., Iceland)

• Volcanic basalt provides resistant cliff faces.
• Past glacial retreat exposes vast plains where sediment has accumulated.
• Active wave erosion leads to isolated stacks and newly developing beaches.

These examples show how the coastal system creates patterns of landforms that together define the landscape.

6. Why Systems Thinking Matters for Coastal Landscapes

Using systems concepts helps explain:

• Why some stretches of coastline erode rapidly while others accrete
• How sediment pathways shape landforms such as spits and bars
• Why human intervention (e.g., groynes, sea walls) often produces unintended consequences
• How global changes (climate, sea level, storms) ripple through coastal processes and landforms
• How landscapes evolve over time, not just in response to physical forces but through interactions with biological, tectonic and human systems
• Systems thinking connects process, place, and change.