Before revision: This dimensionless ratio (the Shields parameter) was first described by Albert Shields and reads: , in which is the critical bottom shear stress; is density of sediment; is the density of water; is the acceleration of gravity; is the diameter of the sediment.
After revision: This dimensionless ratio (the Shields parameter) was first described by Albert Shields and reads: , where: is the critical bottom shear stress; is the density of the sediment; is the density of water; is the acceleration of gravity; is the diameter of the sediment.