Coastal transportation, also known as beach transportation, refers to the movement of sediment (like sand, pebbles, and shells) along a coastline due to wave action and currents. It's how beaches change shape and evolve over time.
Understanding Coastal Transportation
Here's a breakdown of the processes involved:
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Swash: When a wave breaks on the shore, the water rushes up the beach at an angle. This forward movement is called the swash. The angled approach is critical because it picks up sediment along the way.
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Backwash: After the swash reaches its highest point, the water flows back down the beach towards the ocean. This return flow is the backwash. While the swash moves diagonally, the backwash typically moves in a straight line due to gravity.
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Longshore Drift: The combination of the angled swash and the straight backwash results in a net movement of sediment along the beach. This lateral transport of sediment is called longshore drift or longshore transport. This is the primary mechanism for beach transportation.
Factors Affecting Coastal Transportation
Several factors influence the rate and direction of coastal transportation:
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Wave Angle: The angle at which waves approach the shore significantly impacts the direction and speed of sediment transport.
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Wave Energy: Larger, more powerful waves can carry more sediment and transport it further.
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Beach Slope: A steeper beach slope can influence the strength and direction of the backwash.
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Coastal Currents: Currents running parallel to the shoreline can also contribute to longshore transport.
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Sediment Size and Type: Smaller, lighter sediment is more easily transported than larger, heavier sediment.
Impacts of Coastal Transportation
Coastal transportation plays a crucial role in shaping coastlines:
- Beach Erosion and Accretion: The movement of sediment can lead to erosion in some areas and accretion (build-up) in others.
- Formation of Coastal Features: Longshore drift can create features like sand spits, barrier islands, and tombolos.
- Navigation and Sedimentation: Sediment transport can affect navigation channels and contribute to sedimentation in harbors.
