1. FACTOR OF SAFETY Determining slope stability in Holtwood, PA in the aftermath of Hurricane Sandy Kristina Lofman November 27, 2012 EPS 109

2. S = Shear resistance (strength) T = Shear stress C a = apparent cohesion (kPa) γ f = unit weight of soil and field moisture (kN/m 3 ) z = vertical soil depth (soil mantle thickness*cosα) α = slope angle (degrees) Φ = internal angle of friction (degrees) u = pore water pressure at the failure surface (kPa) At failure, S = T Sidle, R. C., & Swanston, D. N. (May 01, 1982). Analysis of a small debris slide in coastal Alaska. Canadian Geotechnical Journal, 19, 2, 167-174. MECHANICS OF FAILURE FACTOR OF SAFETY Pore water pressure is the only value that changes: Increasing precipitation Increasing pore water pressure Decreasing shear resistance

3. To calculate FS for spatial data of slopes, run projectcode.Lofman.m using slope data ( clip_output.txt ) Black: minimal slope Yellow: stable Red (maroon): unstable