To obtain figures and tables for environmental assessment on diffusion caused by dumping dredged materials from fishery ports into the ocean, study on past records on volume of dredging and dumping materials were carried out. The cases for numerical simulation on diffusion were selected by examining the study on past records. The simulation was conducted for conditions of three types of dredged materials, three water depths, three current speeds and one representative median diameter.
As the results of the simulation, figures of maximum concentration, maximum diffusion distance, affecting time on diffusion for 2mg/L and 10mg/L conditions were obtained.
After specifying sorts of fish around the dumping area and fishing time, a trial of prediction on diffusion and assessment for dumping dredged material were conducted by using those figures.
