Which of the following best defines "porosity" in context to materials used in drainage?

The best definition of "porosity" in the context of materials used in drainage is the presence of small openings for liquid passage. Porosity refers to the ratio of the volume of voids (spaces) in a material to its total volume. These voids allow fluids, such as water, to flow through the material. In drainage systems, materials with high porosity effectively facilitate the movement of water, promoting efficient drainage and ensuring that excess water can be managed properly.

This characteristic is crucial for applications where water infiltration and drainage management are needed, allowing for the prevention of flooding and erosion. Thus, understanding porosity helps in selecting appropriate materials for drainage applications, as those with optimal porosity can reduce surface runoff and enhance groundwater recharge.