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<br />Ramsey County | Multi-Jurisdiction Hazard Mitigation Plan 60 <br />Figure 10. Unstable Soils and Bedrock in South Ramsey County <br /> <br />Source: Ramsey 2040 Comprehensive Land Use Plan <br />3.9.3 EXTENT <br />3.9.3.1 Landslide <br />To determine the extent of a landslide hazard, it is essential to identify affected areas and assess the <br />probability of a landslide occurring within a specified period. Key natural variables that influence <br />landslide activity include soil properties, topographic position and slope, and historical occurrences. <br />Predicting landslides remains challenging, even with ideal conditions and reliable data. Consequently, <br />landslide hazards are often represented by landslide incidence and/or susceptibility, as defined below: <br />• Landslide incidence refers to the number of landslides occurring in a specific geographic area. A <br />high incidence indicates that over 15% of the area has experienced landslides. Medium <br />incidence means that 1.5% to 15% of the area has been affected, while low incidence indicates <br />that less than 1.5% of the area has experienced landslides. <br />• Landslide susceptibility refers to the likelihood of geologic formations responding to natural or <br />artificial alterations, such as slope cutting, loading, or unusually high precipitation. Areas with a <br />history of numerous landslides are particularly vulnerable to new movements under these <br />conditions. Susceptibility is influenced by slope angle and the underlying geologic material. It <br />identifies potential landslide-prone areas but does not specify a time frame for when a landslide <br />might occur. High, medium, and low susceptibility are categorized using the same percentages <br />as landslide incidence: over 15% for high, 1.5% to 15% for medium, and less than 1.5% for low.