Theoretical and experimental studies were performed to evaluate the detachment mechanisms of deposited material by fluidizing the filter media. The hydrodynamic characteristics of a backwashed filter and the energy dissipation during backwashing processes were investigated. The existence of a viscous sublayer around each fluidized particle and laminar sublayer thickness at the wall were neglected. Direct measurements of the effluent turbidity T-e and the total backwash water volume V-bt were made during backwashing in the laboratory experiments. Some relationships applicable to backwashing processes were developed with good accuracy. The turbulence parameter C-a(0.5)/Re which characterizes the effect of turbulence fluctuations in a backwashed filter increased with increasing fraction solids (1-epsilon) and decreased with increasing the Reynolds number of the flow Re. The detachment rate of deposited material r(d) was found to vary with hydrodynamic shear (tau (a)) turbulence fluctuations (C-a(0.5)/Re) and backwash water volume (V-b). Maximum shear stress caused a maximum detachment of the deposited material from the filter media. The detachment rate of deposited material r(d) had a minimum value at the turbulent parameter of 0.9 and fraction solids of 0.3. Also the detachment rate of the deposited material r(d) decreased with increasing the unit backwash water volume V-b which is the ratio of the total backwash water volume V-bt to the expanded bed volume V-e.