La Valette harbours (Malta)
Protection of La Valette natural harbours
Client: Infrastructure Malta - Scales: 1/32.6 (2D) - 1/46.6 (3D)
The two natural harbours on either side of Valletta, Marsamxett Harbour to the north-west and Grand Harbour to the south-east, have significant heritage interest. They are also deep, steep-sided, rocky and exposed to waves from three different directions (north-west, north-east and east), making protecting them a particularly complex matter. They accommodate pleasure boating, trade, transport, cruise and naval activities, within severely limited space. There is hence an urgent need to improve operability conditions and protect them during winter storms.
In this context, Infrastructure Malta commissioned Artelia to perform comprehensive hydraulic studies to characterise the current situation, define protection scenarios, draw up a preliminary dimensional design of the solution selected, and check the hydraulic performance and stability of the structures on a physical model.
Artelia performed the hydraulic studies (offshore waves and onshore transformation, wave disturbance inside the harbours, and hydrodynamics), proposed protection solutions, assessed the hydraulic performance of the submerged breakwater using a numerical wave flume, produced the conceptual preliminary dimensional design of the proposed structures (overall layout and sections) and validated this design by performing wave flume and wave tank studies at its Hydraulics Laboratory near Grenoble.
2D physical tests of the submerged breakwater:
- hydraulic stability under extreme wave conditions
- Wave energy dissipation under operational conditions
3D physical tests of the outer breakwater:
- hydraulic stability and overtoppings under extreme wave conditions
- interactions between waves and existing structures
- wave agitation propagating into the harbor entrance
Specific project feature
Protection scenario for Grand Harbour, combining :
- a rubble-mound breakwater in 8 and 12 m3 Accropode™ II units outside the harbour to block the propagation of NW waves
- a detached submerged breakwater in 4 and 6 m3 Accropode™ II units along the shore allowing a significant decrease of the natural shore reflection and consequently the wave disturbance in the harbor entrance