Beach Morphology

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Beaches are coastal landforms that are constantly changing. They are the result of wave action by which waves move sand or other loose sediments and compact and settle in still water. Beach materials are the products of weathering and erosion of rocks offshore, coral reefs and of headlands. Sediments may also be river-borne through the process of coastal erosion. Once compacted, the accumulated sediments are more resistant to erosion. Vegetation establishes shortly after, and their roots will also help resist erosion by slowing the fluid flow at the surface layer. Figure 1. Beach Morphology. The basic morphology of a beach is shown in Figure 1. A berm is a long narrow wedge of sand with its slope towards the water. The berm crest is…show more content…
There is high wave frequency and weak swash, which brings ashore a minute amount of material. Destructive waves tend to be tall waves, meaning they break with great force upon the beach leading to a strong backwash that removes beach material. Ultimately, destructive waves create steep narrow beaches. Constructive waves on the other hand have long periods between their wave crests and low energy. Their swash is much stronger than their backwash, building up the beach with deposited sediments. Constructive waves are long waves and roll on to the beach rather than crashing. Ultimately, constructive waves create wide, gently sloping beaches (Figure 2).
The beach profile undergoes seasonal changes due to change in wave energy. In temperate areas, summer beach profiles are characterized by: calm seas, long periods between breaking wave crests, and increased deposition thus high beach profiles. On the other hand, the winter months have amplified wave energy and increased sediment suspension thus lowering the beach profiles. In tropical areas, this phenomenon is in
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Example of a groin. Wave refraction is another element that affects beaches. Wave refraction is the slowing and bending of waves in shallow water. The portion of the wave in shallow water moves slower than the part in deeper water thus bending the wave. The part of the wave in deeper water eventually catches up to the slower part becoming more parallel to the shore (Komar 1976). Wave refraction can help straighten shorelines. Wave refraction leads to erosion at headlands (Figure 7); material is removed from the headlands and transported into embayments where the wave energy is less, over time smoothing out irregularities.
Figure 7. Headland erosion.
Beach erosion is a current major concern. Natural erosion is a common phenomenon with the sea level eustatically changing. During approximately the past 18,000 years, sea level has risen about 120 m. But human interference has caused an increased rate in erosion. It is estimated that 80% of erosion issues are caused by the human interruption of regular sand transport along the coast (Lindorm). To begin with, the building of dams along rivers has decreased the sediment transport to the beaches at the mouth of the rivers. “Over 100 billion metric tons of sediment and 1 to 3 billion metric tons of carbon are now sequestered in reservoirs constructed largely within the past 50 years” (Syvitski

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