|Improving Flood Map Accuracy
From National Academies Press
A new report from the National Academies Press, Mapping the Zone: Improving Flood Map Accuracy, examines the factors that affect flood map accuracy, assesses the benefits and costs of more accurate flood maps, and recommends ways to improve flood mapping, communication, and management of flood-related data.
Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps portray the height and extent to which flooding is expected to occur, and they form the basis for setting flood insurance premiums and regulating development in the floodplain. As such, they are an important tool for individuals, businesses, communities, and government agencies to understand and deal with flood hazard and flood risk. Improving map accuracy is therefore not an academic question--better maps help everyone.
Making and maintaining an accurate flood map is neither simple nor inexpensive. Even after an investment of more than $1 billion to take flood maps into the digital world, only 21 percent of the population has maps that meet or exceed national flood hazard data quality thresholds. Even when floodplains are mapped with high accuracy, land development and natural changes to the landscape or hydrologic systems create the need for continuous map maintenance and updates.
The report, currently a pre-publication version, was authored by the Committee on FEMA Flood Maps; Board on Earth Sciences and Resources/Mapping Science Committee; National Research Council.
Data quality standards projected to be achieved for individual counties by the end of the Map Modernization Program. Green counties meet or exceed national flood hazard data quality thresholds. Yellow counties meet some standards. In red counties, the maps have been updated digitally.