Dam Failure Inundation Explorer

Overview

The United States has over 92,000 dams. The Army Corps of Engineers classifies 16,805 of them as high-hazard potential — meaning failure would likely cause loss of life. Despite this, most Americans have no idea whether they live downstream of a compromised dam. This explorer maps every high-hazard dam in the National Inventory of Dams (NID), scores each one by structural risk, and estimates the downstream reach of a potential failure using the Froehlich (1995) breach discharge equation.

Data Source

All dam data comes from the National Inventory of Dams (NID), maintained by the US Army Corps of Engineers. The dataset downloaded for this analysis contains 92,445 dams and was last updated March 15, 2026. The NID includes dam name, location, hazard classification, condition assessment, height, storage volume, dam type, year completed, owner, and inspection history.

Dam Risk Score (0–100)

Each high-hazard dam receives a composite risk score based on four factors:

Factor	Weight	Description
Condition Assessment	35%	Unsatisfactory=1.0, Poor=0.85, Fair=0.50, Satisfactory=0.20, Not Rated=0.40
Reservoir Storage Volume	25%	Normalised to 99th percentile; larger reservoirs = more energy if they fail
Dam Age	20%	Older dams score higher; normalised over 120-year range
Dam Height	20%	Taller dams produce higher flood waves; normalised to 99th percentile

Risk Tiers

Risk scores are grouped into four tiers:

• Critical — Score ≥ 70: Worst condition, large storage, old age
• High — Score 50–70: Multiple compounding risk factors
• Elevated — Score 30–50: One or more elevated risk factors
• Moderate — Score < 30: Adequate condition, smaller scale

Froehlich (1995) Breach Discharge Estimate

For each dam with known height and storage, the app estimates the peak breach discharge using the empirical Froehlich equation:

Q_p = 0.607 × V_w^0.295 × h_w^1.24

Where V_w is the reservoir volume in m³ and h_w is dam height in metres. The estimated downstream inundation reach is then approximated as 1 mile per 1,000 m³/s of peak discharge, capped at 20 miles. This is a simplified screening tool — not a substitute for formal dam breach inundation studies.

Important Limitations

• This is a screening-level risk index, not a formal hydraulic analysis.
• Inundation reach estimates are highly simplified — actual flood extents depend on channel geometry, downstream obstacles, and breach mechanics not captured here.
• Condition ratings in the NID reflect the most recent inspection; many dams are rated "Not Rated" due to gaps in inspection data.
• This tool is for public education and research purposes only.

Source Code

Full methodology, data processing notebooks, and source code are available on GitHub.