Breakwaters

Breakwaters

Floating breakwaters have been part of successfully protecting marinas for many years.

Generally speaking, floating breakwaters can provide suitably sheltered conditions for marinas in places where the maximum fetch is about 6 kilometers and the maximum wave period is about 4 seconds. It is important to realise floating breakwaters only reduce the waves, they will never totally remove them.

At Orsta, all breakwaters, in fact all concrete pontoons, are designed especially for a project location. Our breakwaters are not designed to suit the factory or the moulds or even the means of transportation. All Orsta pontoons are designed to meet the site requirements and the clients wishes.

Key Factors for Breakwaters

Wind speed; As bigger waves are the result of greater wind velocity, we distinguish between normal and extreme conditions, where extreme conditions might be described as once in 100 year occurrence. Ideally, breakwaters should be designed to reduce waves to < 35 cm in the marina basin, it might however be advisable to allow for exceptions in extreme conditions, where survivability of the marina and the breakwater is sufficient.

Effective Fetch; Fetch is defined as the distance over which a wind acts to produce waves. Not just the size of the area in front of the proposed breakwater is important, depth, coastline etc. might also have an impact.

Design Wave Height; The wave height is the vertical distance between the trough and the following crest. Most important is the significant wave height, Hs and the wave length L. Hs = significant wave height which represents the average height of the highest third in the incident wave spectrum. It is very rare that data for these two parameters is available based on measurements at the site. Therefore, the values of Hs and L have to be calculated according to the theoretical formulae presented in the professional literature.

On Site Production Capability

At Orsta we specialise in the manufacture of large concrete pontoons ‘on site’, where they are needed, thanks to our ‘in house’ expertise and investment in mobile production resources.

The key benefit of production on site is that the physical size restraints of transportation are avoided enabling us to build very large pontoons to the client’s specific length, width and freeboard requirements. We are able to build individual pontoons up to 8 metres wide and 1.5 metres freeboard. Transportation costs of large concrete pontoons can be very high and therefore by local production we can provide the client with significant savings.

On site manufacture is co ordinated and closely supervised by Orsta’s senior management team using our own production staff supplemented by locally sourced skilled craftsmen and specialist material suppliers.