Laserfiche WebLink
• 3.0 Probability Based Upon Observed Landslide <br />Movements <br />Probabilities for landslide outcomes using observed landslide movements assume a coefficient of <br />variation in the landslide classifications. Each landslide classification has a corresponding <br />movement velocity (which can be measured) and an associated landslide outcome. <br />3.1 Velocity of Landslide <br />The velocity of the landslide was determined before the corrective measures were installed using <br />1997 movement rates, as measured by the survey monitoring points listed in Appendix A Prior to <br />the corrective measures, the maximum landslide velocity in the spring of 1997 was about <br />9 feedyear (average between the head, body, and toe), and the corresponding fall velocity in 1997 <br />was about 0.5 feedyear (average between the head, body, and toe). The measured velocity during <br />the short period of observation since the pins were installed is about 2.5 feedyear (average spring <br />velocity of the head and body only) and .08 feedyear currently (July and August 1998). This data <br />is also presented in Appendix A <br />• 3.2 Landslide Velocity Class (LVC) <br />Based upon Vaznes, the landslide may be classified according to its velocity (Landslide Velocity <br />Classification, LVC). A relationship between the landslide velocity and landslide classification is <br />shown on Figure 5. Figure 6 shows the Varnes scale and the Landslide Velocity Classifications. <br />The LVC can be estimated using the velocities prior to corrective measures in 1997 and after <br />corrective measures in 1998 and using Figure 5. Based upon the measured velocity in 1997, the <br />LVC was 3.1 in the spring and 2.5 in the fall. In 1998, after correction with pins, the LVC was 2.8 <br />in the spring and is currently 2.1. <br />3.3 Coefficient of Variation <br />Assuming a 30 percent coefficient of variation within the LVC values, and assunung that the <br />average LVC value calculated for 1997 and 1998 represent the pre-correction and post-correction <br />LVC, respectively, the probability of the LVC can be determined (i.e., a 30 percent coefficient of <br />variation means that the LVC can vary between about 2 and 4, which seems reasonable). For this <br />analysis, the probability is based upon a normal distribution of values for LVC in the spring using <br />• <br />0626024\60558-UCET 5 <br />