Sediment Transport Gorleston Beach

Sediment transport in the nearshore zone (close to the beach), especially during storm conditions, is predominantly from the beach to offshore with along-shore wave energy being only 10% of the onshore-offshore component. A net southward along-shore drift is dominant, although localised drift reversals can occur under different wave climates. Wave driven along-shore drift occurs predominantly in the surf zone, whilst tidal currents may transport a significant amount of material offshore of the surf zone.

Has there always been a problem?

Following the construction of the harbour piers at Great Yarmouth, and their extension in the early 1960's less beach material was able to reach Gorleston beach from the north. Because the net sediment transport is in a southerly direction the harbour piers trap beach material. As Gorleston beach still loses sand to the south and doesn't receive much material from the north, the beach erodes. This process is known as downdrift erosion. Similarly if too much material is trapped at Gorleston, the beach to the south will suffer from downdrift erosion. This problem can be prevented by placing enough beach material when constructing a coastal defence structure with the objective to trap beach material.

What happens during a storm?

During a storm large waves wash beach material offshore. Because storms occur on a regular basis during the winter, beach levels fluctuate on a seasonal basis.

Winter storm waves moves sand offshore. Summer wave conditions moves sand onto the beach.

At Gorleston this process is not in balance, and as a result more material is carried offshore than onto the beach.

Gorleston Beach before Feb 2000 Storm.

Gorleston Beach after Apr 2000 Storm.

Something to think about.

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