Clean water

Silt laden water

Sandy Loam non colloidal

0.5

0.8

Silt Loam non colloidal

0.6

0.9

Ordinary firm loam

0.8

1.1

Stiff clay

1.1

1.5

Fine gravel

0.8

1.5

Coarse gravel, non colloidal

0.2

1.8

Cobbles

1.5

1.7

Grassed banks

0.9

1.5

Soft rock

1.3

2.5

Hard rock

3.0

4.6

Cement/concrete

4.6

7.6