Shoreform stable bays
These are created by installing offshore islands with a circular planform. A circular island will disturb waves and collect sediment, principally sand, in the patterns shown below.
Wave reflection and diffraction pattern for cylindrical island

Shoreform stable bays
These are created by installing offshore islands with a circular planform. A circular island will disturb waves and collect sediment, principally sand, in the patterns shown below.
Wave reflection and diffraction pattern for cylindrical island
Sediment accumulation pattern
around a cylindrical island
The wave-disturbance pattern shown above applies only to a cylindrical island. All waves reflected from the cylindrical wall emerge as ripples, radiating outwards and dispersing their energy as they go. It is only at the wall itself that they must match the height of the incident waves. The dispersion should allow the incident waves to carry any drift sediment right up to the wall on the seaward side. As soon as this sediment reaches the island wall it will be swept from the seaward to the leeward side. The result of this will be the shoaling pattern shown in the lower diagram. Once a shoaling spit starts to form, given sufficient sand, it will continue to grow naturally.
Physical Model Study
Tank testing was carried out to study the sand accretion pattern. The tank was purpose-built with a shoaling beach and drift-recirculation channels to ensure the absence of wave reflection or drift back to the island. The wave basin was 7.0 m long, 3.5 m wide and 0.4 m deep. This represents a length scale factor of 1:100, with time and velocity factors of 1:10. The test island was placed in the centre of an elevated bed, representing the near-shore location of a full-scale artificial island.
Test tank and cylinder viewed from wave machine end
Side view of wave making machine
Development of waves over the shoaling bed
Development of waves over
the shoaling bed
The wave machine was built to produce waves in deep water (240 mm) with a 1-second period (scaling up to 10 s) and a deep-water height of 40 mm (scaling up to 4 m). Linear theory predicts an increase of height to 50 mm in the passage fr