Sign up to access the complete lesson and track your progress!
Unlock This CourseBeaches are one of the most recognisable coastal landforms, formed when waves lose energy and deposit sediment along the shoreline. They're dynamic environments that constantly change shape due to wave action, tides and human activities. Understanding how beaches work is crucial for coastal management and protecting communities from erosion and flooding.
Key Definitions:
Beaches form when constructive waves deposit more sediment than they remove. This happens in sheltered bays, where wave energy is reduced, or where there's a good supply of sediment from rivers or cliff erosion. The sediment gets sorted by size - larger pebbles stay near the top of the beach whilst finer sand settles lower down.
The shape and composition of beaches depend on several key processes working together. Wave energy, sediment supply and tidal range all play important roles in creating the beach features we see today.
Constructive waves are the main builders of beaches. These low-energy waves have a strong swash that carries sediment up the beach, but weak backwash that can't drag much material back to sea. This creates a net gain of sediment on the beach. The size of sediment deposited depends on wave energy - high-energy waves can move larger pebbles, whilst low-energy waves only transport fine sand.
Low frequency (6-8 per minute), long wavelength, low height. Strong swash, weak backwash. Build up beaches by depositing sediment.
High frequency (10-14 per minute), short wavelength, high height. Weak swash, strong backwash. Erode beaches by removing sediment.
Summer brings constructive waves that build beaches. Winter storms create destructive waves that erode beaches, making them lower and narrower.
Beaches have distinct zones, each shaped by different processes. Understanding these zones helps explain how beaches respond to changing conditions and why some areas are more vulnerable to erosion than others.
From sea to land, beaches typically have several distinct zones. The offshore zone is permanently underwater, the nearshore zone is where waves break and the foreshore is the area between high and low tide marks. Above this is the backshore, which only gets wet during storms or very high tides.
Berm: A ridge of sediment at the back of the beach, formed by the highest waves. Often marks the limit of normal wave action.
Beach face: The sloping section of beach that's regularly covered and uncovered by tides.
Runnel: A shallow channel that runs parallel to the shore, often found on sandy beaches at low tide.
Ridge: A raised area of sand or shingle, usually running parallel to the shoreline.
Chesil Beach is an 18-mile long shingle beach that demonstrates classic depositional processes. The pebbles are graded by size - small pebbles at the western end near Bridport, getting progressively larger towards Portland in the east. This happens because wave energy varies along the beach, with stronger waves able to move larger pebbles further. The beach acts as a natural sea defence, protecting the Fleet Lagoon behind it from wave attack.
Several factors work together to determine what type of beach develops in any location. These include wave energy, sediment supply, coastal geology and human activities.
The type of beach that forms depends heavily on local conditions. Rocky coastlines with limited sediment supply develop narrow, coarse beaches, whilst areas with abundant sand create wide, gently sloping beaches. Tidal range also matters - areas with large tidal ranges have wider beaches because waves can deposit sediment across a broader area.
Rivers bring sediment from inland, cliff erosion provides local material and longshore drift moves sediment along the coast. Areas with good sediment supply develop larger, more stable beaches.
Sheltered areas with low wave energy allow fine sediment to settle, creating sandy beaches. Exposed areas with high wave energy only retain coarse material, forming shingle beaches.
Beaches face increasing pressure from human activities, climate change and sea level rise. Understanding how beaches work is essential for developing effective management strategies that protect both the environment and coastal communities.
Coastal managers use various techniques to maintain beaches and protect them from erosion. These range from 'soft' engineering solutions that work with natural processes, to 'hard' engineering that tries to control coastal processes directly.
Beach nourishment: Adding sand or shingle to replace eroded material. Expensive but effective short-term solution.
Groynes: Wooden or rock barriers built perpendicular to the beach to trap sediment moved by longshore drift.
Beach profiling: Reshaping beaches to make them more effective at absorbing wave energy.
Dune restoration: Planting vegetation to stabilise sand dunes behind beaches, creating natural flood defences.
Bournemouth's beaches are artificially maintained through regular sand replenishment. The council adds around 100,000 cubic metres of sand annually to replace material lost to erosion and longshore drift. Groynes help trap some sediment, whilst beach huts and promenades provide economic benefits that justify the high maintenance costs. This shows how valuable beaches can be managed sustainably, but at significant expense.
Rising sea levels and changing storm patterns pose new challenges for beach systems. Many beaches are already showing signs of stress, with increased erosion rates and more frequent overwashing during storms.
Coastal managers are developing new approaches to deal with changing conditions. These include managed retreat, where development is moved away from vulnerable coastlines and nature-based solutions that use natural processes to provide coastal protection.
Higher sea levels mean waves can reach further inland, potentially eroding the back of beaches and threatening coastal development.
More frequent and intense storms can overwhelm beach defences and cause rapid erosion of sediment built up over many years.
Healthy beaches provide natural flood protection, support tourism and create habitats for wildlife. Protecting these benefits requires long-term planning.