Coastal Landscapes

Flows of Energy and Material in Coastal Systems

Flows of Energy in Coastal Systems

Energy flows are fundamental to the functioning of coastal systems. They drive the processes that shape coastal landscapes and influence the movement of materials.

Wave Energy

  1. Generation:
    • Waves are primarily generated by wind blowing over the surface of the sea. The size and energy of waves depend on wind speed, duration, and fetch (the distance over which the wind blows).
  2. Wave Types:
    • Constructive Waves: These are low-energy waves with a long wavelength and low height. They build up beaches by depositing material.
    • Destructive Waves: High-energy waves with a short wavelength and high height. They erode coastlines by removing material.
  3. Wave Action:
    • Breaking Waves: When waves approach shallow water, they slow down, increase in height, and eventually break. This releases energy, which erodes, transports, and deposits materials.
    • Swash and Backwash: The movement of water up (swash) and down (backwash) the beach affects sediment transport and beach morphology.

Tidal Energy

  1. Tidal Cycles:
    • Tides are caused by the gravitational pull of the moon and sun. They follow a regular cycle of high and low tides, typically occurring twice daily.
  2. Tidal Currents:
    • Tidal movements create currents that transport sediments and influence coastal processes. Tidal ranges (the difference between high and low tide) affect the extent of tidal action.

Solar Energy

  1. Heating:
    • Solar radiation heats the land and sea, influencing evaporation, weather patterns, and biological processes.
  2. Weather Systems:
    • Solar energy drives atmospheric circulation, affecting wind patterns, storm formation, and precipitation. These factors contribute to coastal erosion and sediment transport.

Flows of Material in Coastal Systems

Material flows in coastal systems involve the movement of sediments and organic matter. These flows are essential for the development and evolution of coastal landforms.

Sediment Transport

  1. Sources of Sediment:
    • Fluvial: Rivers bring sediments from inland areas to the coast.
    • Marine: Waves and currents transport sediments along the coastline.
    • Aeolian: Wind carries sediments from land to the coast, particularly in arid regions.
  2. Transport Mechanisms:
    • Longshore Drift: Sediments are moved along the coast by wave action at an angle, creating a zigzag pattern.
    • Traction: Larger particles roll along the seabed.
    • Saltation: Medium-sized particles bounce along the seabed.
    • Suspension: Fine particles are carried within the water column.
    • Solution: Dissolved materials are transported in the water.

Deposition

  1. Conditions for Deposition:
    • Deposition occurs when the energy of transporting forces decreases, allowing sediments to settle. This happens in sheltered areas, such as bays and estuaries, or when wave energy is low.
  2. Deposition Features:
    • Beaches: Accumulations of sand, pebbles, and other sediments along the shoreline.
    • Spits: Narrow landforms extending from the coast into the sea, formed by longshore drift.
    • Bars: Ridges of sediment that form parallel to the coast, often creating lagoons.

Biological Material

  1. Organic Inputs:
    • Organic matter from plants and animals contributes to the coastal system. This includes detritus from marine organisms, plant material from coastal vegetation, and waste products.
  2. Ecosystem Influence:
    • Coastal ecosystems, such as mangroves, salt marshes, and coral reefs, play a crucial role in trapping and stabilizing sediments. They also provide habitats for various species, influencing biological processes and material flows.