The higher the annual rainfall, the greater the number of periods of heavy rainfall. The steeper the topographic slope, the faster will be the velocity of storm water runoff, other things being equal. Soil Type . More rainfall will soak into sandy soils than into clay soil. Hence, for a given rainfall intensity, the volume of runoff will be greater from areas underlain by clays or other low permeable soils than from permeable sandy soils.
Velocity tends to decrease as stream width increases.
Merging streams, eddy currents, and curves in streams are other factors that may reduce the velocity. Generally, the shorter the distance from the lead deposit to the property line, the more likely it is that lead fragments in suspension will be transported off-site. Shooting directly over a water body ensures that the lead reaches the water. Vegetative cover and man made structures like dams and dikes reduce the water's velocity and greatly reduce the size and weight of the lead particles the water can carry. Since lead particles are heavy compared to the other suspended particles of similar size, they are more likely to be deposited under the influence of anything that reduces velocity of the storm runoff.