SECTION 4: RISK ASSESSMENT
Probability of Future Occurrence From 1995 through 2018 there have been 11 landslide events in the planning area, which equates to an annual probability of 45.8 percent. This probability applies to Wake County and jurisdictions in western Wake County, but reflects only the probability of a minor event. Jurisdictions in eastern Wake County that do not have any historical occurrences or susceptibility are unlikely to experience any landslide events in the future. Across all areas of the county, the probability of a severe landslide event is unlikely. Probability: 1 – Unlikely Climate Change Per the Fourth National Climate Assessment, frequency and intensity of heavy precipitation events is expected to increase across the country. Additionally, increases in precipitation totals are expected in the Southeast. Increased flooding may also result frommore intense tropical cyclone; researchers have noted the occurrence of more intense storms bringing greater rainfall totals, a trend that is expected to continue as ocean and air temperatures rise. More rainfall falling in more intense incidents could contribute to an increase in landslide events.
Vulnerability Assessment Methodologies and Assumptions
This assessment of vulnerability to landslide in Wake County was based solely on records of past events. Data on susceptibility is limited for the planning area and only available in an area-wide aggregate. People People are unlikely to sustain serious physical harm as a result of landslides in Wake County. Impacts would be relatively minor and highly localized. An individual using an impacted structure or infrastructure at the time of a landslide event may sustain minor injuries. Property Landslides are infrequent in Wake County and occur in small, highly localized instances relative to the general area of risk. Additionally, these events are generally small scale in terms of the magnitude of impacts. As a result, it is difficult to estimate the property at risk to landslide. On average, a landslide event in the planning area may cause minor to moderate property damage to one or more buildings or cause localized damage to infrastructure. A landslide event may also result in the need for debris removal. Environment Because landslides are essentially a mass movement of sediment, they may result in changes to terrain, damage to trees in the slide area, changes to drainage patterns, and increases in sediment loads in nearby waterways. Landslides in Wake County are unlikely to cause any more severe impacts. Consequence Analysis
Table 4.43 summarizes the potential negative consequences of landslide. Table 4.43 – Consequence Analysis - Landslide
Category
Consequences
Public
Any impacts to the public are expected to be minor. Individuals may sustain injuries if they are in an affected structure or using affected infrastructure when the event occurs. Impacts to responders are unlikely. Personnel responsible for debris cleanup or roadway closures may face increased risk.
Responders
Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019
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