TABLE 6.1 Benefits and Costs of Improved Map Accuracy





Land use: floodplain regulations

Reduced loss of life

  • Able to target higher-risk areas

  • Able to identify evacuation needs


Reduced loss of property

  • Able to target higher-risk areas

  • Lower-risk areas less restricted

  • Building restrictions match risk

  • Less time and money spent on contesting maps

  • Eventual payback on freeboard costs

  • Wise floodplain investment, including infrastructure

  • Increased construction costs

  • Loss of land to development

  • Need to update regulations and inform the public of changes

Reduced loss of business

  • Fewer business interruptions

  • Fewer public service interruptions

  • Increased construction costs

Preservation of natural functions of floodplains

  • Natural storm water management

  • Improved water quality

  • Increased ecological diversity

  • Loss of land to development



  • Structures insured at appropriate levels

  • More consistent insurance ratings through better information about risk

  • Rates may increase for some


  • More insurance purchased because of improved understanding of risk


Property values


  • Lower (or no) devaluations because of better information on risk

  • Change in practices that have led to devaluations


Emergency services

Resource deployment

  • More efficient allocation in planning and response


SOURCE: Compiled from FEMA (1997) and NRC (2006).

others for insurance purposes, land management, mitigation, risk assessment, and disaster response.2 Because these uses are not mutually exclusive, it is appropriate to sum the benefits, as is done in conventional benefit-cost analyses (e.g., NRC, 2006).

Several categories of benefits emerge from benefit-cost analyses of flood maps (FEMA, 1997; NCFMP, 2008) and work on flood and seismic hazards (Bernknopf et al., 1993; Chivers and Flores, 2002; NRC, 2006). Most of these benefit categories arise from improvements in both horizontal accuracy (i.e., proper depiction of the floodplain boundary) and vertical accuracy (i.e., proper assessment of risk), although the nature and level of benefits may differ for each type of accuracy. These benefit categories and their associated costs are summarized in Table 6.1 and described below.

Land Use

More accurate flood maps provide a more reliable measure of risk and enable floodplain managers to better target land use regulations. Owners of properties that were incorrectly designated within the floodplain benefit by having building restrictions lifted or lessened, which will lower future construction costs, eliminate mandatory retrofitting, and enable the land to be used in more ways. Adding building and land use restrictions to properties that should have been designated within the floodplain can lead to measures to protect equipment, inventories, and personal possessions. Although up-front costs are higher, developing and using land commensurate with the true risk will reduce future losses of life, property, and business. A benefit-cost analysis of National Flood Insurance Program (NFIP) building standards in coastal areas found that the benefits of freeboard exceed the construction costs by 3 to 7 percent (Jones et al., 2006).

Another possible benefit of more accurate maps is that fewer individuals will contest floodplain boundaries and levels of risk, saving time and money. Greater trust in the maps could also lead to more, but wiser, investment. Finally, management of floodplains to preserve important natural functions (e.g., slowing storm water runoff, buffering water quality) benefits the entire community. Although some work has been done on valuing


Presentation to the committee by Paul Rooney, FEMA, on August 20, 2007.

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