Which property describes the ease of fluid flow under pressure in soils or rocks?

Permeability is the property that describes the ease with which fluids can flow through soils or rocks when pressure is applied. It is a critical factor in hydrogeology and geotechnical engineering because it determines how water moves through different materials. A high permeability indicates that fluids can move easily, while low permeability surfaces impede fluid movement.

This property is particularly important when designing structures that interact with water, such as dams, roads, and foundations, as well as in the assessment of groundwater resources and contamination. It also plays a role in understanding natural processes like drainage and aquifer recharge. Understanding permeability helps engineers and scientists determine how quickly aquifers can be replenished or how contaminants might spread through subsurface materials.

The other choices refer to different characteristics: hydraulic gradient relates to the change in pressure with distance, porosity refers to the volume of voids in a material, and saturation describes the extent to which the pores in a material are filled with water. While all these factors are interconnected in the context of fluid movement, permeability specifically focuses on the ease of flow.