Impermeable

Impermeable is an adjective used to describe a material or barrier that does not allow the passage of liquids or gases. The word comes from Latin impermeabilis, meaning not penetrable.

In geology and hydrogeology, impermeable layers impede groundwater flow. Common examples include clay-rich soils, shale, and unfractured rock. Such layers are called aquitards or confining beds and can separate aquifers or prevent the movement of contaminants.

In construction and engineering, impermeable barriers prevent leaks and seepage. They are used in foundations, waterproofing membranes, liner systems for landfills, reservoirs, tunnels, and underground structures. The impermeability is quantified by properties such as the permeability coefficient; design often aims for very low values to meet specifications.

In textiles and consumer products, impermeable fabrics block water ingress. Some waterproof garments use impermeable coatings or membranes, though many modern garments are designed to be waterproof yet breathable. The term is sometimes used more broadly to describe anything resistant to water or liquids.

Environmental planning notes that impermeable surfaces like asphalt and concrete reduce infiltration and increase surface runoff, contributing to flooding. Urban design may employ permeable pavements, green roofs, or other strategies to balance impermeable barriers with controlled water management.