1st and 2nd Derivatives The derivative evaluation is performed on a profile basis along the 4 cardinal directions. Since the NW/SE direction reveals the typical shape of the rotational landslide, the steepest slope “S” direction was excluded from this evaluation. The investigation of the derivatives revealed that abrupt changes in elevation along the DEM could be identified by analyzing the profile shapes. The profile for the typical shaped rotational slide shown in Fig 9.3 exhibits a higher first and “S” second order derivative than all the other profiles occurring. Note the signal response is strong where the scarp is located. In comparison, the second derivative is clearly better indicator than the first derivative. All other profiles do not exhibit a particular trend or pattern that identify unique surface features. Figure 9.3. All profile derivatives for landslide 1 Subsequently, profiles were evaluated for two different cases, shown in Table 9.1, along the areas surveyed. The main difference between the two cases is that case 2 includes more evaluations compared to case 1, thus computationally it is more costly. The parameters given in each case are shown in Table 9.1. Parameter Case1/Case2 Description Angle Interval (°) 15.00 /5.00 Angle between profiles from E to W 123.00(37.49 m)/123.00(37.49 Profile Length (ft) The total length of the profile m) Spacing Easting (ft) 20.50(6.25 m)/16.40(5.00 m) Spacing between locations tested Spacing Northing 61.50(18.75 m) /16.40(5.00 m) Spacing between locations tested (ft) Profile Spacing (ft) 0.82(0.25 m)/0.82(0.25 m) Spacing between points on profile Table 9.1. Parameter selection for landslide classification From analyzing the typical shaped rotational slide of landslide 1, a criterion was determined “S” to identify scarp-like features. The constraint values selected are shown in Table 9.2. Parameter Constraint 1st Derivative (ft/ft) 1.00 (0.30 m/m) or -1.00 (-0.30 m/m) ≥ ≤ 2nd Derivative (0.03 m/m2) or -0.10 (-0.03 m/m2) ≥ 0.10 ≤ (ft/ft2) Table 9.2. Constraints for landslide classification
1st and 2nd Derivatives The derivative evaluation is performed on a profile basis along the 4 cardinal directions. Since the NW/SE direction reveals the typical “S” shape of the rotational landslide, the steepest slope direction was excluded from this evaluation. The investigation of the derivatives revealed that abrupt changes in elevation along the DEM could be identified by analyzing the profile shapes. The profile for the typical “S” shaped rotational slide shown in Fig 9.3 exhibits a higher first and second order derivative than all the other profiles occurring. Note the signal response is strong where the scarp is located. In comparison, the second derivative is clearly better indicator than the first derivative. All other profiles do not exhibit a particular trend or pattern that identify unique surface features. Figure 9.3. All profile derivatives for landslide 1 Subsequently, profiles were evaluated for two different cases, shown in Table 9.1, along the areas surveyed. The main difference between the two cases is that case 2 includes more evaluations compared to case 1, thus computationally it is more costly. The parameters given in each case are shown in Table 9.1. Parameter Case1/Case2 Description Angle Interval (°) 15.00 /5.00 Angle between profiles from E to W Profile Length (ft) 123.00(37.49 m)/123.00(37.49 m) The total length of the profile Spacing Easting (ft) 20.50(6.25 m)/16.40(5.00 m) Spacing between locations tested Spacing Northing (ft) 61.50(18.75 m) /16.40(5.00 m) Spacing between locations tested Profile Spacing (ft) 0.82(0.25 m)/0.82(0.25 m) Spacing between points on profile Table 9.1. Parameter selection for landslide classification From analyzing the typical “S” shaped rotational slide of landslide 1, a criterion was determined to identify scarp-like features. The constraint values selected are shown in Table 9.2. Parameter Constraint 1st Derivative (ft/ft) ≥ 1.00 (0.30 m/m) or ≤ -1.00 (-0.30 m/m) 2nd Derivative (ft/ft2) ≥ 0.10 (0.03 m/m2) or ≤ -0.10 (-0.03 m/m2) Table 9.2. Constraints for landslide classification