Wake County Hazard Mitigation Plan - January 2020


Vulnerability Assessment This section quantifies, to the extent feasible using best available data, assets at risk to natural hazards and potential loss estimates. People, properties and critical facilities, and environmental assets that are vulnerable to the hazard are identified. Future development is also discussed in this section, including how exposure to the hazard may change in the future or how development may affect hazard risk. The vulnerability assessments followed the methodology described in the FEMA publication Understanding Your Risks — Identifying Hazards and Estimating Losses (August 2001). The vulnerability assessment first describes the total vulnerability and values at risk and then discusses vulnerability by hazard. Data used to support this assessment included the following:  Geographic Information System (GIS) datasets, including building footprints, topography, aerial photography, and transportation layers;  Hazard layer GIS datasets from state and federal agencies;  Written descriptions of inventory and risks provided by the State Hazard Mitigation Plan; and  Written descriptions of inventory and risks provided by the previous Wake County Multi- Jurisdictional Hazard Mitigation Plan.  Exposure and vulnerability estimates provided by the North Carolina Emergency Management IRISK database.  Crop insurance claims by ca use from USDA’s Risk Management Agency NCEM’s IRISK database incorporates county building footprint and parcel data. F ootprints with an area less than 500 square feet were excluded from the analysis. To determine if a building is in a hazard area, the building footprints were intersected with each of the mapped hazard areas. If a building intersects two or more hazard areas (such as the 1-percent-annual-chance flood zone and the 0.2-percent-annual- chance flood zone), it is counted as being in the hazard area of highest risk. The parcel data provided building value and year built. Building value was used to determine the value of buildings at risk. Year built was used to determine if the building was constructed prior to or after the community had joined the NFIP and had an effective FIRM and building codes enforced. Census blocks and Summary File 1 from the 2010 Census were used to determine population at risk. This included the total population, as well as the vulnerable elderly and children age groups. To determine population at risk, the census blocks were intersected with the hazard area. To better determine the actual number of people at risk, the intersecting area of the census block was calculated and divided by the total area of the census block to determine a ratio of area at risk. This ratio was applied to the population of the census block. For example, a census block has a population of 400 people. Five percent of the census block intersects the 1-percent-annual-chance flood hazard area. The ratio estimates that 20 people are then at risk within the 1-percent-annual-chance flood hazard area (5% of the total population for that census block). Two distinct risk assessment methodologies were used in the formation of the vulnerability assessment. The first consists of a quantitative analysis that relies upon best available data and technology, while the second approach consists of a qualitative analysis that relies on local knowledge and rational decision making. The quantitative analysis involved the use of NCEM’s IRISK database, which provides modeled damage estimates for flood, wind, and wildfire hazards. Vulnerability can be quantified in those instances where there is a known, identified hazard area, such as a mapped floodplain. In these instances, the numbers and types of buildings subject to the identified hazard can be counted and their values tabulated. Where hazard risk cannot be distinctly quantified and modeled, other information can be collected in regard to the hazard area, such as the location of critical

Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019


Made with FlippingBook - professional solution for displaying marketing and sales documents online