Hazard is about what’s downstream
Every dam gets a hazard classification based on what its failure would do, not on how likely failure is. A dam in excellent condition can still be High hazard if a town sits below it. Condition is rated separately.
Failure would probably cost lives
People live or work in the path of the water. These dams face the most frequent inspections and are expected to keep an emergency action plan.
Failure would cause major damage
No expected loss of life, but flooding could take out roads, bridges, utilities or property downstream.
Failure would cause limited damage
Losses would fall mostly on the dam owner’s own property, with no expected loss of life.
What each dam page shows
Safety ratings
Hazard potential and condition assessment, side by side, with the condition scale explained from best to worst.
Emergency plans
Whether an emergency action plan is on file. High hazard dams are expected to have one; the inventory shows which do.
Inspection history
The date of the most recent inspection on record, and how long ago that was.
The structure
Height drawn to scale, length, storage, dam type, owner, and the year it was completed.
Browse by state
The red bar is the share of each state’s dams rated high hazard.
Rankings
Oldest Dams
Dams dating back to the 1600s — centuries of American infrastructure.
Tallest Dams
America's highest dams, towering hundreds of feet above their foundations.
Largest Reservoirs
The biggest reservoirs in the U.S., ranked by storage capacity.
High Risk Dams
High hazard dams with poor or unsatisfactory condition ratings.
Understanding Dam Safety Data
Every dam in the National Inventory of Dams receives a hazard potential classification based on the consequences of failure — not the likelihood. A "High" hazard dam is one where failure would probably cause loss of human life. This classification determines inspection frequency, emergency action plan requirements, and regulatory oversight.
Condition assessments rate the physical state of the dam: Satisfactory means no deficiencies recognized, Fair means minor issues being addressed, Poor means recognized deficiencies requiring remediation, and Unsatisfactory means serious deficiencies requiring immediate attention.
DamLookup.com makes this public safety data searchable by address, state, and county so you can understand the dam infrastructure near you.