Gabions are tools of the engineering geologist, facing elements that are used to stabilize over-steep slopes, such as sea cliffs or railway/roadway cuttings; they also have military applications. The word is derived from the French, gabion, and Italian, gabbione, and originally referred to “A wicker basket, of cylindrical form, usually open at both ends, to be filled with earth, for use in fortification and engineering” (Little et al., 1983, p. 823). A modern gabion used in engineering geology is a cage, box or cylinder, commonly infilled by rocks or concrete, and sometimes sand or soil (https://en.wikipedia.org/wiki/Gabion).
Essentially, gabions provide a stable retaining wall that is semi-permanent. That is, they can be more easily removed, modified or replaced than a permanent structure made in concrete, brick or steel. Although they may be aesthetically unpleasing, gabions provide stability in situations where serious erosion problems may exist, which cannot be controlled by alternatives such as re-vegetation (Freeman and Fischenich, 2000). This is a simplification and studies such as that of Druse (2015) explain something of the complexities.