Wave refraction significantly shapes the coastline by concentrating wave energy on some areas while reducing it in others.
Understanding Wave Refraction
Wave refraction is the process where a wave changes direction as it approaches the shore. This happens because different parts of the wave crest travel at different speeds as the water depth varies. When waves approach an irregular coastline with headlands (protruding land) and bays (indented areas), they bend.
Impact on Coastal Features
The bending of waves due to refraction has a distinct impact on the shape and erosion rates of the coastline:
- Headlands: As waves approach a headland, the parts of the wave crest in shallower water near the headland slow down more than the parts in deeper water on either side. This causes the wave crests to bend and converge on the headland. Consequently, the wave energy is concentrated on the headland. Headlands of a coastline are exposed to the full force of destructive waves. This concentrated energy leads to increased erosion of headlands.
- Bays: Conversely, the parts of the wave crest entering the deeper water of a bay travel faster than the parts approaching the shallower headlands. This causes the wave crests to diverge and spread out as they enter the bay. Bays are more sheltered from the wave energy because of wave refraction close to the shore.
Erosion Rates
The uneven distribution of wave energy due to refraction directly affects erosion rates:
- Headlands: Experience high wave energy and therefore undergo faster erosion.
- Bays: Benefit from the scattering of wave energy, meaning erosion is slower. The reference specifically notes that because of wave refraction close to the shore, erosion is slower in bays. This relative protection allows for sediment deposition, often resulting in the formation of beaches within bays.
| Coastal Feature | Wave Energy | Erosion Rate | Primary Impact |
|---|---|---|---|
| Headland | High | Faster | Erosion |
| Bay | Lower | Slower | Deposition |
This differential erosion and deposition process, driven by wave refraction, tends to straighten irregular coastlines over time. However, as the coastline straightens, wave refraction effects decrease, leading to a complex and dynamic interplay between waves and landforms.
