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National Inventory of Dams

National Inventory of Dams (Photo by AGC)

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­Description and Background

The National Inventory of Dams (NID) is a congressionally authorized database, which documents dams in the U.S. and its territories. The NID was most recently reauthorized in the Dam Safety Act of 2006.  The current NID, published in 2013, includes information on 87,000 dams that are more than 25 feet high, hold more than 50 acre-feet of water, or are considered a significant hazard if they fail.  The NID is maintained and published by the U.S. Army Corps of Engineers (USACE), in cooperation with the Association of State Dam Safety Officials (ASDSO), the states and territories, and federal dam-regulating agencies. The database contains information about the dam’s location, size, purpose, type, last inspection, regulatory facts, and other technical data. The information contained in the NID is updated approximately every two years.

Data Overview

The 2013 NID includes information on approximately 87,000 dams of which 80 percent are regulated by the State Dam Safety Offices and almost 70 percent of the entire inventory is privately-owned dams. The federal government owns or regulates 6 percent of the total NID, which includes approximately 35 percent of the tallest dams.  Dams in the NID are classified according to hazard potential, an indicator of the consequences of dam failure.  A dam’s hazard potential classification does not indicate its condition.  The NID lists 14,726 dams classified as high hazard potential, 12,406 significant hazard potential, 58,956 low hazard potential and 1,271 undetermined.  Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life. Significant hazard potential are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss. Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/ or environmental losses. Losses are principally limited to the owner’s property. More than 27,000 (32 percent) of the dams listed in the NID have a primary purpose of recreation and more than 15,000 (17 percent) are primarily for flood damage reduction and storm water management.

Website Access

The website enables query of dams using any of the 70+ fields of information, including dam name, height, type, purpose, year of construction, and owner, with query results shown on screen.  Users can also display and query dams using the interactive map and show relevant features, such as state, county, congressional boundaries, waterways, and major cities.  To query the database, users must request an account from the NID Website,, Request a Username.  After a short approval process, users will receive an email notification with username and password.  There is a short PowerPoint tutorial available from the Interactive Report as well as other help documentation on the Interactive Map function.

Point of Contact

NID Data Team
Geospatial Systems Directorate
Civil Application Branch