Increasing climate change impact to natural disasters is important to be evaluated for changes in coastal hazard extremes, such as mean sea levels and surface temperatures because higher exposure of coastal zones increases their disaster risk. Objective of the study is developing methods and simulating for dynamical downscaling of coastal current system for Ibaraki coast in Japan from 10 km scale reanalysis to related projections of 222 m scale with included freshwater impact from three major rivers. Its application is to formulate techniques for providing fine scale ocean circulation reanalysis and future projection which can be used for adaptation of countermeasures for climate change impact assessment. COAWST model, consisting of hydrostatic ocean model (ROMS) and spectral wave model (SWAN), is used for dynamical downscaling. The coastal current was downscaled by COAWST model using 3 domain nesting with 2 km, 667 m and 222 m scales, for targeted reanalysis period of whole 2000. The downscaled data was validated by in-situ observed data. We found that the downscaling model can precisely simulate related projections of coastal currents and other ocean parameters on the fine scale of 222 m with better precision than with the coarse scale parent reanalysis model and that surface velocities at Hasaki have quick and strong response to northward surface velocities at Cape Choshi originating from the Kuroshio Current. The changes in surface temperature due to downscaling are significant for shallow water environment due to heat radiation effects rather than momentum advection. The freshwater impact to surface temperature is mostly negligible but it can have significant impact to reducing surface salinity which consequently changes water density and ocean circulation patterns. The freshwater impact to storm surge heights is negligible before and during the Typhoon Kirogi passage but is important to be considered in evaluating the after-runner storm surge mechanism.