Since the 1960s, the importance of marine utilization and development has been pointed out. Various approaches for this purpose have been taken, but the progress remains inadequate. One of the reasons is the lack of infrastructure at sea as a hub. Therefore, marine hub ports should be constructed on remote islands including Minamitorishima Island and Okinotorishima Island to promote marine utilization and development.

However, these remote islands are surrounded by severe sea wave environment and severe sea climate for port construction which are different from those of general ports in main islands. Further technological development is required to ensure smooth ship berthing, cargo-handling, and port construction.

Therefore, in this research theme, we will make maximum use of previously accumulated knowledge regarding waves, seabed soils, port structures, and port construction to construct ports on remote islands, and will also promote marine utilization and development. Specifically, we will clarify the characteristics of waves in isolated reef areas, and will develop a new mooring system for ships. We will also develop technologies for downsizing and reducing the weight of underwater acoustic video cameras, as well as utilization and development.

We will develop a wave calculation model for wave transformations on continental shelf boundaries and around isolated islands. We will also propose a technology to create calm water areas against wave propagation and long-period waves around isolated reefs. At the same time, we will develop a new mooring system applicable to remote islands to improve cargo-handling efficiency for ships.

We are trying to downsize and lighten underwater acoustic video cameras, and will also develop an unmanned underwater construction system to construct marine infrastructure. In addition, we will propose an environment protection technology by promoting the attachment of calcifies to structures.

In an innovation for using berthing and mooring facilities constructed in isolated coral reef sea, we used the coupling model between a wave hindcasting model (WAM) and a wave transformation model (NOWT-PARI) to estimate the occurrence frequency of ocean waves around isolated islands. Then, we compared the estimated occurrence frequency with ocean wave data from 1-year observations around the Minamidaitojima Island and Kitadaitojima Island and verified the cargo-handling operation rate at quays. Also, we used CADMAS-SURF/3D, which was improved to simulate moored ship motion, to estimate the oscillation magnitude of each moored ship at isolated reef areas.

In a technological development on advanced ship mooring system in port, we devised a suction-connection combination method, steel mooring fender method, wire strings method, and other methods. Of these methods, we selected the wire strings method as a highly suitable mooring method under remote island conditions.

In a research on maintenance inspection and investigation technology for remote island ports, we proposed a management method. In the method, we associated inspection underwater photographs with information including the location of photographing. Also, regarding methods of measuring the location information of an underwater running body, which is required at the time of management, we proposed a method of combining acoustic positioning equipment, GNSS, ground speed meters, and hydraulic gauges. In addition, in a simulated experiment of photographing objects placed in a water tank, we demonstrated that the dimensions of subjects, deformation, and others can be measured using underwater photographs, which are taken with the use of parallel line laser radiation.

In a research on adaptation of the machine guidance for an underwater excavator, we added an acoustic profiler and decided to conduct pre-measurement of rubble mound shapes. Also, we conducted unit tests of acoustic positioning equipment at the actual construction site and confirmed that multiple reflection and noise do not have a significant impact. In addition, we conducted comprehensive tests at Keihin dockyard and confirmed that disparities of seafloor surface coordinates (height) are ±32 mm or less.

In a development of next-generation acoustic imaging system, we organized the specifications of deep/shallow underwater acoustic video cameras as specifications that can withstand real sea-area conditions. Regarding deep underwater acoustic video camera, we conducted verification tests at Takuyo Daigo seamount, an investigation site near Minamitorishima and then succeeded in taking acoustic images at the depth of 1500 m. Also, regarding shallow underwater acoustic video camera, we conducted trial operations through public works at Minamihonmoku and succeeded in taking acoustic images steel pipe sheet piles.

In a field observations and analyses on the formation and stability of carbonate lands, we succeeded in estimating ground formation rate on scales ranging from several days to seasons in model site investigations; moreover, we elucidated determinants of calcification rates, which greatly affects the ground formation speed. Also, we used the existing core-sample specimens and succeeded in estimating the ground formation rates on a scale of the past 1000 years. With this success, we proposed a quantitative model of the maintenance conditions of low-water lines. In addition, in a coral coexistence-type tide pool at Urazoe breakwater of Naha Port, we elucidated that the following factors are important environmental conditions to increase coral coverage: levels of disturbance due to water depth, water flow, waves; and gradient and shapes (complexity level) of the coral-adhering surface.