Development of a monitoring system of red-silt outflow from the Okinawa Island based on satellite remote-sensing data

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Recent aggravation of the problems related to the outflow of the eroded silty red-soil from the Okinawa Island and its subsequent deposition on the coral reef needs more comprehensive and quantitative monitoring system to analyze their actual situation. For this purpose, in this study, a new methodology mainly based on LANDSAT/TM data has been developed with the emphasis that the monitoring system to be developed should be based on proper theoretical backgrounds and thereby have wide applicability to various image data taken at different locations and times. The monitoring system developed has been applied to detect the water-depth distribution and the turbidity due to red-silt in coral-reef area. Besides, as the main object of the monitoring, the spatial cover rate of the seabed surface due to the sediment deposition has been analyzed without any appreciable dependence on the difference in color of the sediment deposited. The results of these analyzes have shown satisfactory good agreements with field data, demonstrating the validity and the wide applicability of the present methods.