Wave Energy and Coastal Processes

Wave energy determines whether coastlines experience erosion or build up new landforms. Waves gain their power from three key factors: wind strength, wind duration, and fetch (the distance wind travels over water).

Constructive waves are your beach-builders. They have low energy, arrive 6-9 times per minute, and create gentle beach gradients perfect for seaside holidays. Their strong swash (water flowing up the beach) carries sediment inland, whilst their weak backwash (water flowing down) leaves most material behind.

Destructive waves are the cliff-carvers. These high-energy waves crash ashore 11-15 times per minute with powerful backwash that drags sediment seaward. They create steep beach profiles and are responsible for dramatic coastal erosion.

Quick Tip: Remember constructive waves construct beaches, whilst destructive waves destroy cliffs!

Longshore drift moves sediment along coastlines when waves approach at an angle. The swash carries material diagonally up the beach, but gravity pulls the backwash straight down, creating a zigzag transport pattern that shapes our coasts over time.

Erosional Processes and Landforms

Four main erosional processes attack coastal rocks with relentless force. Hydraulic action compresses air into rock cracks, acting like a pneumatic drill. Abrasion occurs when waves hurl rocks against cliffs like natural hammers. Attrition gradually rounds pebbles as they collide with each other, whilst corrasion uses chemical reactions to dissolve vulnerable rocks like chalk.

These processes create spectacular erosional landforms. Wave-cut notches form at cliff bases, eventually creating overhangs that collapse and leave behind wave-cut platforms - those flat, rocky areas exposed at low tide.

Headlands and bays develop where resistant rocks stick out whilst softer rocks get carved into curved inlets. Over thousands of years, headlands can be sculpted into caves, then arches, stacks, and finally stumps as erosion continues its relentless work.

Remember: Erosional landforms follow a sequence - headland → cave → arch → stack → stump.

Subaerial processes also shape coasts through weathering (rock breakdown without movement) and mass movement (downslope movement including rockfalls, slumps, and flows).

Depositional Landforms and Transportation

When wave energy drops, deposition creates fascinating coastal features. Spits form when longshore drift deposits sediment across bay mouths, often developing curved ends where waves bend around them. If a spit connects an island to the mainland, it becomes a tombolo.

Beaches vary dramatically based on wave energy. Sandy beaches result from constructive waves on low-energy coasts, whilst pebble beaches form where destructive waves create steep profiles. Salt marshes develop in sheltered estuaries where fine sediments settle in calm waters.

Bars can form parallel to coastlines when destructive waves wash sediment seaward. Hooked spits curve landward, sometimes enclosing lagoons, whilst cusped forelands create triangular shapes where longshore drift operates in opposite directions.

Key Insight: Coastal alignment matters - swash-aligned coasts face waves head-on with limited drift, whilst drift-aligned coasts experience consistent longshore movement.

Transportation processes move sediment in four ways: suspension (fine particles floating in water), solution (dissolved minerals), traction (large boulders rolling), and saltation (small stones bouncing along). Flocculation helps clay particles clump together and sink in salty water, contributing to mudflat formation.