In this review paper the changes of hydraulic gradient in the flow characteristics is presented. The analysis has been obtained in the value of loaded effective stress in soft soil. The relationship between flow velocity and hydraulic gradient is nonlinear. The results of soft soils used to the analysis were obtained in laboratory using the flow-pump technique. To describe the permeability characteristics the prelineary and postlineary phases should be considered. The prelineary phase characterises the flow at very low hydraulic gradient which usually appears in situ. The permeability characteristics show the strong changes of hydraulic gradient under different values of effective stress.