This study presents an investigation of the changes of the currents in Kwangyang Bay due to the construction of harbor, reclamation and coastal developments. Currents were simulated by the numerical experiments with a diagnostic multi-level model and using the seasonal oceanographic data of temperature, salinity and ocean current. The values of kinetic and potential energies for the currents were calculated in cases of three topographical changes; before coastal developments, the existing state and after completion of the development project in Kwangyang Bay. The changes of currents due to the coastal developments are as follow; Kinetic energies of tide induced residual currents and wind driven currents decreased by 35~40 percent and 5 percent respectively, however those of density currents increased by 10 percent since the decrease of the coastal areas. Kinetic energy of residual currents including tide induced residual currents, density currents and wind driven currents reduced by 10 percent compared with before the coastal developments. Decrease of current velocity was greatest in summer. Therefore, in summer it was assumed that the Kwangyang Bay is more easily polluted by stratification and decrease of residual current than before the coastal developments carried out.