The northeastern portion of Ohio is categorized as a region of high landslide susceptibility and hazard potential. The areas that are most susceptible to landslides are located along steep-sided valleys and along roads cuts through weak glacio-lacustrine silts and clays. Landslide hazard includes any direct or indirect hazard posed to humans and properties because of landslide activity. In order to identify slopes exhibiting varying degrees of hazard potential, and to help engineers prioritize their remediation efforts, this dissertation proposes a new landslide hazard rating system for Northeastern Ohio.
Forty nine slopes with different hazardous levels (low, moderate, high) were selected for development of the hazard rating system. The slopes were selected so that they were representative of the variations of geometric, geologic, hydrologic, and traffic conditions in the study area. Twelve parameters were initially considered for developing the landslide hazard rating system. These parameters were divided into three groups: the soil-related and hydrologic group, the slope-geometry related group, and the traffic-related group. Univariate, bivariate, and cluster analyses were performed on the collected data to identify parameters that were most significant in distinguishing between slopes of varying hazard potential. The statistical analysis identified six of the twelve parameters as statistically significant. These six parameters were included in the final rating system. In addition, three other parameters that were not found to be statistically significant but
have been shown to be important by the existing rating system were retained in the final rating system.
The nine parameters used in the final landslide hazard rating system for northeast Ohio include liquidity index, recharge area, slope height, slope length, slope angle, average daily traffic, decision sight distance, degree of vehicle risk, and length of roadway affected. Based on site condition, each parameter in the system was assigned scores using an exponential scale (3, 9, 27, 81), with the total score for a given slope being the sum of the scores for individual parameter.
According to the rating scale, the minimum scores should not be less than 27 and the maximum scores could not exceed 729. The lowest score a site in the study area scored is 87 and the highest score is 567. Based on hazard criteria discussed in the dissertation and field observations of hazard potential, sites with scores < 200 were categorized as low hazard potential sites, those with scores between 200 and 300 as moderate hazard potential sites, and those with scores > 300 as high hazard potential. The final system rated 23 sites as low hazard potential sites, 15 sites as moderate hazard potential sites, and 11 sites as high hazard potential sites whereas field observations at the start of the study categorized 26, 13, and 10 sites belonging to the low, moderate, and high hazard potential categories, respectively.