The breaking down and undermining of part of a hillslope, triggering small slips. Sapping is significant in valley formation (Nash (1996) ESPL21, 9). See Twidale (2007) Revista C. & G. 21, 1–2 on sapping at a river bluff. For sapping erosion, see Fernández et al. (2008) Geomorph. 95, 3–4.
Subjects: Earth Sciences and Geography.