Nigeria: Modelling Coastal Defenses by HR Wallingford

A 3D scale model of a Nigerian beach near Lagos has been put through its paces this month in HR Wallingford’s modelling hall.

New coastal defenses are needed where the beach has retreated at the residential Maiyegun Beach Estate following major development farther along the coast.

The designers of the coastal protection scheme, CDR International, asked HR Wallingford to build the model to show how the proposed sea defenses would influence the response of the beach.

“Constructed in one of our wave basins, the model represents an embayment between two groynes with a low crested breakwater between them. The bathymetry (or seabed) has been replicated in the vicinity of the breakwater and model sand was used to recreate the beach,” HR Wallingford said.

“Our engineers investigated alternative designs of the low-crested breakwater structure and the response of the beach behind the structure. The scheme was tested under five sea states – the first two represented the frequently occurring conditions on the beach and the other three represented more extreme storms, with less frequent return periods. After each test the model was surveyed by a 3D laser scanner.”

HR Wallingford has also carried out 2D modelling in one of their flumes to collect further data about the breakwater section, using a combination of wave transmission and armor stability testing.