Wave deposition is the process by which sediment, eroded and transported by waves, is left behind when the energy of the waves decreases. This leads to the build-up of landforms such as beaches, spits, and bars.
Here's a breakdown of the process:
Understanding Wave Action
First, it's important to understand how waves transport sediment. Waves erode coastal materials through processes like hydraulic action and abrasion. This eroded material becomes sediment that is then carried by the waves.
Where Deposition Occurs
Deposition primarily happens where wave energy diminishes. Several factors can cause this:
- Shallower Water: As waves approach shallower water, friction with the seabed increases, slowing the wave down.
- Sheltered Areas: Bays, inlets, and areas behind headlands are protected from the full force of the waves, leading to reduced energy and deposition.
- Changes in Wave Direction: Waves that refract (bend) around headlands can lose energy as they spread out.
- Tidal Influences: Changes in tide levels affect water depth and therefore wave energy.
The Sorting of Sediment
A key aspect of wave deposition is the sorting of sediment by size and weight:
- Larger Particles (e.g., pebbles, gravel): These heavier materials are typically deposited closer to the shore where wave energy is still relatively high. They require more energy to be transported further.
- Smaller Particles (e.g., sand, silt, clay): Finer sediments are carried further offshore into calmer waters before settling. This is because they require less energy to remain suspended.
Landform Creation
Wave deposition is responsible for creating various coastal landforms:
- Beaches: The most common depositional feature, formed by the accumulation of sand and other sediments along the shoreline.
- Spits: Long, narrow ridges of sand or shingle that extend from the mainland into the sea or across an estuary mouth. They form when longshore drift deposits sediment where the coastline changes direction.
- Bars: Similar to spits, but they connect two headlands, creating a lagoon on the landward side.
- Tombolos: A bar of sand or shingle that connects an island to the mainland.
Summary
In summary, wave deposition is the process where waves drop the sediment they are carrying because their energy has decreased. The size of the sediment deposited depends on the wave energy, with larger particles deposited closer to the shore and finer particles deposited further out in calmer waters. This process creates various coastal landforms like beaches, spits, and bars.
