This paper describes a new tool to measure, in situ, the engineering and environmental characteristics of unconsolidated seabed materials, particularly carbonate tropical sands, as much as 15 meters thick in water depths to a maximum of 20 meters from a small unanchored vessel. The initial prototype uses a pneumatic hammer to drive a video camera probe into the seabed. During penetration, the tool, which is shaped like a wood chisel, slices through the unconsolidated material leaving a virtually undisturbed face exposed to the camera. A selection of other physical, chemical and electrical sensors can be used to measure properties and composition of the sediments. In comparison with traditional sampling technology, it is anticipated that the cost of data acquisition may be reduced by an order of magnitude with this system. Although conceived for the characterization of offshore carbonate sand deposits, this unique tool will be adaptable to the characterization of other sites both on land and in the seabed.
Sandy beaches in the tropical Pacific are, for the most part, derived from the erosion products of corral reefs surrounding islands. The sand budget is limited to the production of the reef corals and, in many places, the removal of beaches by storms or by commercial entities for the construction of infrastructure has resulted in serious degradation of the beaches with no hope of timely replenishment by natural means (Cruickshank, 1997). Shoreline loss in the State of Hawaii, and particularly O'ahu, is presently occurring at a significant rate. In 1997, "massive degradation" of Oahu's coast was reported with about 24% of the island's original 100 km of sandy beach "either gone or so narrowed that at high tide it is unusable" (HA, 1997).
