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Impervious materials are characterized by their inability to allow water to pass through them. This means they do not allow water flow under hydrostatic pressure, which is the pressure exerted by a fluid at equilibrium due to the force of gravity. Since impervious surfaces, like concrete or asphalt, do not permit water infiltration, they lead to the accumulation of surface water rather than allowing it to seep into the ground. This property can significantly affect drainage patterns and water management strategies in urban planning and landscape design, as it can contribute to increased surface runoff and potential flooding.

In comparison, the other options reflect characteristics of permeable materials or processes. Materials that allow water to flow freely or promote infiltration (often found in vegetated areas or permeable pavements) directly contrast the definition of impervious surfaces. Additionally, while impervious materials do enhance surface runoff potential, the most accurate description of their primary property is their inability to permit water flow under hydrostatic pressure.