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Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
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Appendix

B Glossary

1 percent annual chance [exceedance] flood—A flood that has a 1 percent chance of being equaled or exceeded in any given year; also known as the “100-year flood” or “base flood” (http://www.fema.gov/national-flood-insurance-program/definitions)

Average annual loss—Expected long-term loss, which is obtained by multiplying the probability of an event by its expected loss and summing over all possible events (GFDRR, 2009)

Base flood elevation (BFE)—The elevation of surface water resulting from a flood that has a 1 percent chance of being equaled or exceeded in any given year (http://www.fema.gov/national-flood-insurance-program/definitions)

Catastrophe model—A computer-based model that estimates losses from natural or manmade hazards, such as earthquakes, floods, hurricanes, and acts of terrorism (Grossi and Kunreuther, 2005)

Credibility weighting—A statistical analysis that combines theoretical damage with observed damage results. When sufficient claims exist to provide statistical confidence in observed results, the depth–damage relationship is based on the claims data. When claims data are insufficient, the claims data and theoretical damage are combined using a weighting process (http://www.fema.gov/media-library-data/20130726-1748-25045-4777/hazusmr5_fl_tm.pdf)

DED—A term in the NFIP actuarial rate formula to eliminate that portion of the loss that will be borne by the policyholder through his or her deductible (FEMA, 2013d)

DELV—A term in the NFIP actuarial rate formula that estimates damage to the property, expressed as a percentage of the total property (replacement) value, resulting from a specified depth of water (FEMA, 2013d)

Depth grid—A grid is a digital raster dataset that defines geographic space as an array of equally sized square cells arranged in rows and columns. The value in each cell represents the magnitude in that location of the flood depth represented by that particular grid (http://www.fema.gov/media-library-data/1406747117357-744b6bd203c18ada4806ad4e90c18b81/Flood_Depth_and_Analysis_Grids_Guidance_May_2014.pdf)

Detailed studies—Flood hazard mapping studies that are done use hydrologic and hydraulic methods that produce base flood elevations, floodways, and other pertinent flood data (https://www.fema.gov/pdf/floodplain/nfip_sg_appendix_d.pdf)

Elevation Certificate—A certificate that verifies the elevation data of a structure on a given property relative to the ground level. It is used by local communities and builders to ensure compliance with local floodplain management ordinances and is also used by insurance agents and companies in the rating of flood insur-

Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×

ance policies (https://www.floodsmart.gov/floodsmart/pages/glossary_A-I.jsp)

Exceedance probability—Probability that a random event will exceed a specified magnitude in a given time period, usually 1 year unless otherwise indicated (http://www.fema.gov/media-librarydata/20130726-1553-20490-8579/dl_flow_app2.pdf)

EXLOSS (expected loss ratio)—A term in the NFIP actuarial rate formula, which serves as a loading factor for underwriting expenses, a contingency factor, and other factors (FEMA, 2013d)

Exposure—The number of people and value of property that might be harmed by inundation (CDWR and USACE, 2013)

Flood depth—Height of flood waters above the surface of the ground at a given point (http://www.fema.gov/pdf/fima/pbuffd_appendix_b.pdf)

Flood duration—Amount of time between the initial rise of flood waters and their recession (http://www.fema.gov/pdf/fima/pbuffd_appendix_b.pdf)

Flood elevation—Height of flood waters above an elevation datum plane (also called water surface elevation; http://www.fema.gov/pdf/fima/pbuffd_appendix_b.pdf)

Flood hazard—Frequency of occurrence of excess water (large flow rates, high stages, or both) at a location. Commonly, this is represented with flow– or stage–frequency relationships (how severe and how often floods occur) at specific locations (CDWR and USACE, 2013)

Flood Insurance Rate Map (FIRM)—The official map of a community prepared by FEMA that shows the Special Flood Hazard Areas, the base flood elevations, and the flood risk zones applicable to the community. The following designations are made for insurance rating purposes:

  • Post-FIRM building—A building constructed or substantially improved after December 31, 1974, or after the effective date of the initial Flood Insurance Rate Map of a community, whichever is later
  • Pre-FIRM building—A building constructed or substantially improved on or before December 31, 1974, or before the effective date of the initial Flood Insurance Rate Map of the community, whichever is later (http://www.fema.gov/national-flood-insurance-program/definitions)

Flood protection measure—Those physical works for which funds have been authorized, appropriated, and expended and which have been constructed specifically to modify flooding in order to reduce the extent of the area subject to a “special flood hazard” and the extent of the depths of the associated flooding. These systems typically include hurricane tidal barriers, dams, reservoirs, levees, or dikes (http://www.fema.gov/medialibrary-data/20130726-1922-25045-4455/20130703_approachdocument_508.pdf)

Flood risk—Risk is the potential for an unwanted outcome. The flood risk to economic activity is the chance that individuals will lose property due to flooding. The risk is measured by economic metrics, such as direct and indirect costs (Traver et al., 2014)

Floodplain—Any land area susceptible to being inundated by flood waters from any source (http://www.fema.gov/national-flood-insurance-program/definitions)

Fragility curve (or function)—Describes the likelihood of flooding due to a levee breach, given the loading on the water side of the levee (CDWR and USACE, 2013)

Full-risk premium rate—A rate charged to a group of policies that results in aggregate premiums sufficient to pay anticipated losses and expenses for that group; also referred to as an actuarial rate (http://www.fema.gov/national-flood-insurance-program/definitions)

LADJ—A factor in the NFIP actuarial rate formula to account for loss adjustment expenses (FEMA, 2013d)

Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×

Lidar (light detection and ranging)—A remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to Earth. These light pulses—combined with other data recorded by the airborne system—generate precise, three-dimensional information about the shape of Earth and its surface characteristics. Lidar terrain data are used in hydraulic models of the floodplain (http://oceanservice.noaa.gov/facts/lidar.html)

Lowest floor—The lowest floor of the lowest enclosed area (including basement) of a building (http://www.fema.gov/national-flood-insurance-program/definitions#L)

Negatively elevated structure—A structure in the Special Flood Hazard Area with the lowest floor elevation below the base flood elevation

PELV—A term in the NFIP actuarial rate formula that estimates the annual probability that flood waters will reach or exceed a given depth relative to the base flood elevation (FEMA, 2013d)

Performance—The effectiveness of flood or floodplain management measures (CDWR and USACE, 2013)

Replacement value—The current cost of a similar new item having the closest usage to the item being replaced. The item does not need to be replaced with an exact replica including all the item’s deficiencies, superadequacies, or obsolescence (USACE, 1995)

Special Flood Hazard Area—Portion of the floodplain subject to inundation by a 1 percent annual chance [exceedance] flood (http://www.fema.gov/pdf/fima/pbuffd_appendix_b.pdf)

Subsidized premium rate—A rate charged to a group of policies that results in aggregate premiums insufficient to pay anticipated losses and expenses for that group (http://www.fema.gov/national-flood-insurance-program/definitions)

UINS—A term in the NFIP actuarial rate formula to adjust for how much policyholders have underinsured their property (FEMA, 2013d)

Vulnerability—The susceptibility of people and property to be harmed from the hazard (i.e., how flooding adversely affects people and property; CDWR and USACE, 2013)

Zone—A geographical area shown on a Flood Hazard Boundary Map or a Flood Insurance Rate Map that reflects the severity or type of flooding in the area (http://www.fema.gov/national-flood-insurance-program/definitions)

Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×

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Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×
Page 69
Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×
Page 70
Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×
Page 71
Suggested Citation:"Appendix B: Glossary." National Research Council. 2015. Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain. Washington, DC: The National Academies Press. doi: 10.17226/21720.
×
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Floods take a heavy toll on society, costing lives, damaging buildings and property, disrupting livelihoods, and sometimes necessitating federal disaster relief, which has risen to record levels in recent years. The National Flood Insurance Program (NFIP) was created in 1968 to reduce the flood risk to individuals and their reliance on federal disaster relief by making federal flood insurance available to residents and businesses if their community adopted floodplain management ordinances and minimum standards for new construction in flood prone areas. Insurance rates for structures built after a flood plain map was adopted by the community were intended to reflect the actual risk of flooding, taking into account the likelihood of inundation, the elevation of the structure, and the relationship of inundation to damage to the structure. Today, rates are subsidized for one-fifth of the NFIP's 5.5 million policies. Most of these structures are negatively elevated, that is, the elevation of the lowest floor is lower than the NFIP construction standard. Compared to structures built above the base flood elevation, negatively elevated structures are more likely to incur a loss because they are inundated more frequently, and the depths and durations of inundation are greater.

Tying Flood Insurance to Flood Risk for Low-Lying Structures in the Floodplain studies the pricing of negatively elevated structures in the NFIP. This report review current NFIP methods for calculating risk-based premiums for these structures, including risk analysis, flood maps, and engineering data. The report then evaluates alternative approaches for calculating risk-based premiums and discusses engineering hydrologic and property assessment data needs to implement full risk-based premiums. The findings and conclusions of this report will help to improve the accuracy and precision of loss estimates for negatively elevated structures, which in turn will increase the credibility, fairness, and transparency of premiums for policyholders.

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