What structure is made of wire mesh and stone, used for erosion control?

A gabion is a structure constructed from wire mesh that is filled with stones, typically used for erosion control and stabilizing slopes. The design allows for flexibility and permeability while effectively resisting soil erosion caused by water or wind. Gabions can absorb the energy of flowing water, which protects the soil beneath from being washed away. They effectively promote vegetative growth and can enhance the aesthetic aspects of a landscape when planted with vegetation.

In contrast, a filter strip is an area of vegetation that helps filter out pollutants from runoff but does not serve the same structural purpose as a gabion. A foundation refers to a structural element that supports load-bearing walls, and does not relate to erosion control. Free water typically refers to water that exists in a free state in the environment, often in reference to hydrology, and is not an erosion control structure. Therefore, the gabion is the correct answer as it specifically addresses the needs of erosion control using a mesh and stone composition.