Chris Brown†, 2013. Monitoring and Maintenance of Plymouth Breakwater
This Breakwater now has four zones of discrete armour: -
the submerged foreshore rock slope
tidal berm – rock partially covered by 100te precast concrete blocks known as Wavebreakers at a coverage of between 40 and 80% deposited from unique catamaran pontoon
an impermeable fitted masonry carapace over the crown of the Breakwater from LWM to LWM
on the lee side, rock from LWM to the seabed
Concerns have long been raised regarding the stability of both roundheads, the foreshore berm and the 100te Wavebreakers on the berm. Although records of placement of materials exist from 1839 to date, these do not allow accurate estimation of movement to be made. Nor do repetitive cross-sectional surveys, as made between 1840 and 1995, allow any more than a gross approximation of volume change to be made, and then only at discrete sections.
Recent developments with GPS, aerial LIDAR and sonar bathymetry have allowed much greater accuracy in offshore surveying than in the past and for the first time an integrated digital baseline survey of the Breakwater was undertaken in 2011, to a sub-aerial accuracy of better than 10cm. Using this, a new basis for monitoring the breakwater is available. The potential for this work to be accompanied by both desk and model studies to determine the limits of stability and the service performance of the Breakwater, so that a final profile can be confirmed and its integrity demonstrated would be greatly enhanced by input from the academic community.
