Scarp seems the likeliest:

1. Fortif. = ESCARP n. 1. 1589 P. IVE Pract. Fortif. 10 The scarpe that the Curtin will make may bee some 28. foote, or more or lesse. 1654 COKAINE Dianea IV. 280 On the top they [the walls] are made after the fashion of a scarpe. 1709 LUTTRELL Brief Rel. (1857) VI. 471 The enemy..lye 2 leagues off behind the scarp. 1876 BANCROFT Hist. U.S. III. xiii. 199 The left extended to a scarp surmounted by an abattis.

b. The total pitch or 'batter' of a bank. Obs. 1639 R. NORWOOD Fortif. 113 If the ditch be dry it must be the deeper, and have the lesse scarpe. 1669 STAYNRED Fortif. 7 The Inward Scarp of the Parapet... The outward Scarp of the Rampire... The Scarp of the Ditch.

2. The steep face of a hill; = ESCARP n. 2. 1802 PLAYFAIR Illustr. Huttonian Theory 410 The scarps of the hills face indiscriminately all points of the compass. 1901 H. TRENCH Deirdre Wed 32 Far up, where darkling copses over-grow Scarps of the gray cliff from his river'd base.

(Oxford English Dictionary)