A seabed platform for long-term monitoring in the littoral environment

A seabed installed instrument platform was previously designed and evaluated using scale modeling techniques; and a prototype has now been built and tested in the coastal ocean environment. The purpose of the platform is to provide protection from mobile fishing gear for instruments and other sensors permanently installed in the seabed, and connected to shore via buried submarine telemetry cables. The half-scale prototype unit is constructed of steel reinforced concrete attached to a steel base extension. It is 2.0 m in diameter, protruding 0.6 m above the seabed, and includes a thin steel skirt penetrating 0.6 m into the seabed. The skirt provides additional resistance to lateral displacement caused by forces applied during interactions with mobile fishing gear. The bottom edge of the skirt is equipped with a jetting manifold that allows installation of the unit using low pressure water into unconsolidated littoral sediments of sands and muds. The results of the interaction experiments with commercial inshore trawl nets, scallop dredges and hydraulic clam dredges indicate no displacement of the platform