Advanced Mooring Systems

There is increased interest among the boating community in alternative mooring systems and the replacement of conventional sinkers and risers with more technically advanced designs. As these are perceived to have significant benefits for the environment, they have been referred to as eco-moorings in the past. However, there are a number of potential advantages for users as well – both mooring owners and boat users – so the term Advanced Mooring Systems (AMS) has now come into use.

There are two main elements to AMS, and either or both can be applied. The first is the replacement of the “sinker” with a helical screw fixed into the seabed. This is already common practice for larger moorings such as in the Thames estuary, but is not in common use for yacht moorings. The second main component is the riser.

The helical screw offers a number of advantages, both technical and environmental:

• When installing the screw, it is straightforward to measure the torque required to drive the last few turns. This reveals, via a simple formula, the holding power of the screw. This is a huge advance over the standard sinker, where the uncertainty of holding results in over-sized blocks being used.
• The screw fixing has a far lower impact on the seabed and any sensitive habitats given its smaller dimensions
• The lower size of the unit means many more can be carried on a workboat increasing the efficiency of operations
• Inspection and replacement is a simple process, although on deeper moorings it may be necessary to employ divers

The riser (rode) is where more research is being undertaken, in order to address technical and environmental concerns:

• A floating or elastic rode does not scour the seabed around the mooring, reducing the impact on habitats such as sea grasses
• However, the AMS needs to replace the damping effect of the chain of a conventional mooring
• There are two main approaches. One is to add floats to the chain, holding it off the seabed. This retains the damping effect while reducing scour. However, ensuring that the additional floats remain attached and don’t cause pollution can be a challenge.
• The more advanced approach is to have an elastic rode. This is more expensive, but has the potential advantage of increasing mooring density. Concerns remain about longevity and developing inspection methods that warn of potential failure (which is straightforward for chain wear).

Various combinations of sinkers, screws, floating chains and elastic rodes are being trialled around the UK and further afield. Research is on-going, though most experiences to date have been positive. The RYA is a partner in an EU LIFE funded project, led by Natural England, called ReMEDIES – Reducing and Mitigating Erosion and Disturbance Impacts affecting the Seabed. One element of the scheme is the installation of trial AMS, alongside a monitoring programme. The RYA’s involvement is focused on outreach to the recreational boating community through The Green Blue, its joint environmental programme run in conjunction with British Marine.

The RYA will continue to be actively involved in projects researching AMS, and we are interested in people’s views on their suitability. If you have experience (good or bad!) of using or installing such systems then please let us know via environment@rya.org.uk