Coastal Processes | Geography for GCSE/IGCSE - Year 11 PDF Download

Coastal regions 

In coastal areas, several key concepts shape the interaction between land and sea:

• Coast: This term refers to the meeting point of land and sea.
• Coastline: It defines the edge of the land, indicated by the high-water mark on low-lying coasts or the base of steep slopes.
• Shore: The shore encompasses the region between the lowest and highest tide marks.
• Tides: These natural phenomena occur approximately twice daily, showing variations based on location and time of year.
• Tidal Range: The tidal range highlights the contrast between low and high tide levels.
• Waves: The movement of waves and currents plays a significant role in shaping coastal features.

Waves

• Waves in the ocean are processes responsible for wearing away, moving, and depositing materials.
• They are generated when wind blows across the surface of the sea.
• The size of a wave is influenced by:
  • The speed of the wind.
  • The fetch, which is the distance over which the wind travels.
  • The duration for which the wind blows consistently in one direction.
  • Greater wind strength, longer durations, and increased fetch result in larger waves.
• When a wave nears the coast and encounters shallower water, friction with the seabed causes it to incline forward, leading to the wave cresting and breaking on the shore.
• The forward movement of water up the beach is known as the swash, while the backward movement is termed the backwash.

• Speed: Refers to how fast the wind is blowing.
• Fetch: Represents the distance traveled by the wind.
• Time: Signifies the duration for which the wind blows in a consistent direction.

Types of Waves

• Destructive waves: These waves erode the beach due to their short wavelength, high-frequency rate, and steep wave gradient. The backwash of destructive waves is stronger than their swash, leading to the removal of material out to sea.
• Constructive waves: Unlike destructive waves, constructive waves are beach builders. They possess a long wavelength, low-frequency rate, and a shallow wave gradient. The swash of constructive waves is stronger than their backwash, resulting in the transportation and deposition of material onto the beach.

Comparison of Wave Type

Marine erosion

• Destructive waves are the primary agents of coastal erosion.
• They erode coastlines through four main processes: Hydraulic Action, Attrition, Corrosion, and Abrasion.
• The impact of attrition intensifies when waves transport sediment over longer distances and durations.
• Over time and with increased water exposure, large, coarse boulders gradually erode into rounded sand grains, primarily composed of quartz.
• Rounded pebbles found on beaches are commonly referred to as shingle.

Marine Transportation

• The ocean transports sediment much like a river, receiving material from various sources:
  • Erosion from cliffs
  • Transport via longshore drift along the coastline
  • Carried inland from offshore by constructive waves
  • Conveyed to the coastline by rivers
• Once in the water, the material is transported through different mechanisms:
  • Traction
  • Saltation
  • Suspension
  • Solution

Longshore Drift

• This process serves as the primary mode of transportation along the coastline.
• Wave direction is influenced by prevailing winds, causing waves to approach the beach at an oblique angle.
• Upon breaking, the swash carries material up the beach at the same oblique angle.
• Subsequently, the backwash carries the material down the beach perpendicular to the shoreline (at a 90° angle).
• This cycle repeats, resulting in the transportation of material along the beach in a zigzag pattern.

• Along coasts with consistent longshore drift in a particular direction, beach sediment is transported over longer distances.
• When sediment movement is obstructed, it prevents sediment from reaching areas further down the coast.
• This creates two problems:
  a. Reduction in the size of beaches, making them less appealing to tourists and resulting in income loss.
  b. Diminishing natural coastal defenses.

Marine Deposition

• Waves transport sand or shingle as they move.
  • Swash carries sediment onto the beach, while backwash carries it away.
• Constructive waves deposit larger material along the upper reach of the swash as they carry sediment up the beach.
• As the backwash returns down the beach, it loses energy due to water loss through the sand's porosity.
• Consequently, sediment deposition becomes progressively smaller, resulting in the beach being sorted by wave deposition, with the finest particles settling offshore in low-energy environments.
• During storms with destructive waveforms, large shingle is thrown above the typical high tide level, forming a ridge known as a berm at the beach's top.