The critical shear stress required to initiate sediment motion depends on ­

(1) particle size or grain size,

(2) particle density relative to the density of water (sediment specific gravity),

(3) particle shape of individual particle (angular or rounded or other shape), ­

(4) porosity of the deposits of which those particle are a part,

(5) degree of clay mineral content as clay mineral tend to bind grains, and

(6) cohesiveness as indicated by degree of cementation between the grains or other means other than by clay contents.