FAQ's on Dams, Dam Safety, etc.

1. What is the largest dam in the U.S.?

Dams can be measured a variety of ways. A typical measure of dam size is by the height of the structure. Other measures include the volume of the structure (e.g., how much concrete is there), or the size of the reservoir. The largest by height are: Click here

2. What are the largest dams in the world?

The largest by height

3. How often do dams fail?

No one really knows exactly how many dams fail or how often, because our methods of identifying and reporting failures has not been complete over the years. However, based on available data, the failure rate of dams of all sizes, types, etc. tends to be on the order of one failure per ten thousand dam years of operation. The failure rate for individual dams can vary substantially from this average rate.

4. Who regulates dams in the U.S.?

The regulatory structure of dams in the U.S. is divided between the federal government and the states. The Federal Energy Regulatory Commission regulates hydroelectric projects. The states regulate all non-federal dams. The states regulate approximately 94 percent of the dams in the country. Dams owned by federal agencies are self-regulated.

5. How many dams are there in the U.S.?

Based on the 1998-1999 update of the National Inventory of Dams, there are 76,926 dams.