Define the Coefficient of Permeability: (K)

A measurement of the ability of the soil or an aquifer for the movement of water through it. Also termed "hydraulic conductivity", Clay and granite have low K values, are tightly packed, therefore have few pore spaces for water movement. Gravel has large openings between aggregate and water can move freely, larger K.   

Table: Typical Permeability

Units are typically (gal/day-ft²) or (ft³/day-ft²) or (ft/sec)