Before Regret · Research
A county-by-county summary of what the US Army Corps of Engineers’ National Inventory of Dams records for the 17,049 dams it classifies as high hazard potential: how each is rated for condition, and whether an emergency action plan is recorded on file. All figures are the assessments of the regulating agencies themselves.
Interactive · 2,274 counties
Every US county with at least one dam classified high hazard potential. Type a county to see how many it has, and what the inventory records for their condition ratings and emergency action plan status.
High-hazard dams in
“High hazard potential” is a classification of what would be at stake if a dam failed. It is not an assessment of how likely any dam is to fail, and it is not a safety ranking. A county with a higher count is generally a county with more dams and more development below them, not a county in danger. These figures describe records, not risk.
Dams in the National Inventory of Dams carry a hazard potential classification. The highest of these, high hazard potential, is assigned where failure would be expected to result in loss of life. It is a classification of potential consequences, based on what lies downstream. It is expressly not an assessment of the dam’s condition, and not a statement that failure is likely.
17,049 dams carry that classification. The inventory separately records a condition assessment for many of them, and separately again records whether an emergency action plan is on file — the document setting out notification procedures in the event of an emergency.
Those three fields are published together, but the inventory does not summarise them against one another. This page does that, at county level, and nothing more. Every classification, rating and status reported here was assigned and recorded by the relevant regulating agency. None of it is our assessment, and we have not inspected, evaluated or formed any view about any dam.
Of the 17,049 dams classified high hazard potential, 2,791 — 16.4% — have a recorded condition assessment of Poor or Unsatisfactory: 2,287 Poor and 504 Unsatisfactory. These are the inventory’s own rating categories, applied by the regulating agency responsible for each dam.
A further 3,784 (22.2%) have no condition rating recorded in this release — entered as not rated, not available, or left blank. A missing rating in the published file indicates that no assessment is recorded here. It does not establish that no assessment exists, and it says nothing about the condition of the dam.
An emergency action plan is a procedural document. It sets out who is notified, and in what order, if a dam emergency occurs, and it commonly includes inundation mapping. Whether one is on file is recorded in the inventory as a separate field from condition.
2,476 dams classified high hazard potential (14.5%) are recorded as having no emergency action plan on file. Of those, 636 also carry a condition assessment of Poor or Unsatisfactory. That overlap is the narrowest group this summary identifies.
Two limits on reading that number. The field reflects what has been reported to the inventory, so an absent record is not proof that no plan exists at the operator or state level. And an emergency action plan is a notification procedure, not a physical measure — its presence does not make a dam safe, and its absence from the record does not make a dam unsafe.
The dams in that group have a median recorded completion year of 1955, and 90.8% of those with a year recorded were completed before 1980 (n = 2,353).
This is a description of the group’s age, not an explanation of its condition ratings. The inventory does not publish the reasoning behind any assessment, and age alone does not determine condition: the same file contains dams of similar vintage rated Satisfactory. We have not tested why any dam holds the rating it holds, and this page does not attempt to.
77.4% of dams classified high hazard potential have an emergency action plan recorded (13,201 of 17,049). The median high-hazard dam in the file has a last inspection date in 2023, and among those rated Poor or Unsatisfactory the median condition assessment date is also 2023.
That context belongs alongside every figure above. These records indicate an inspection and reporting regime that is active and current for most dams in the classification. The smaller groups described on this page were identified by that regime, by the agencies operating it, and recorded in its own published file. This page counts those records. It does not evaluate the agencies, the dams, or the adequacy of any programme.
Hazard classification describes consequences, not probability. This is the most important limitation on the page. A dam classified high hazard potential is not a dam predicted or expected to fail. The classification reflects what is downstream if failure were to occur. A well-maintained high-hazard dam may be in better condition than a low-hazard one. Nothing here ranks any dam by likelihood of failure, and no figure should be read as doing so.
This is not a safety assessment. We are not engineers, we have not inspected any structure, and we express no opinion on the safety, integrity or management of any dam, operator or agency. Every rating reproduced here is the recorded determination of the responsible regulating authority, reported as published.
Records may be incomplete or out of date. The inventory is compiled from submissions by many federal and state agencies on differing schedules. A blank or absent value indicates what the file contains, not what exists in the world. Ratings and plan status change, and this page is a snapshot of the 2026-08-28 release.
Ratings are not issued by a single authority. Most dams are regulated by their state, and states differ in inspection practice, frequency, and where the boundary between rating categories falls. Counts should not be read as a like-for-like comparison between states.
The inventory does not publish downstream population. This release contains no population-at-risk field, so nothing here indicates how many people or homes are below any dam, and no such inference should be drawn.
High-hazard dams by state, with how many are rated Poor or Unsatisfactory, how many lack an emergency action plan, and how many are both.
| State | High-hazard | Poor/Unsat | No EAP | Both |
|---|---|---|---|---|
| NC | 1,678 | 247 | 635 | 120 |
| TX | 1,648 | 217 | 328 | 70 |
| GA | 556 | 193 | 60 | 38 |
| SC | 679 | 162 | 168 | 62 |
| PA | 788 | 145 | 37 | 10 |
| NM | 255 | 145 | 115 | 80 |
| MS | 349 | 140 | 40 | 25 |
| OH | 421 | 132 | 81 | 36 |
| NY | 451 | 116 | 3 | 2 |
| KY | 277 | 106 | 8 | 1 |
| IN | 282 | 91 | 126 | 46 |
| HI | 118 | 88 | 3 | 1 |
| KS | 328 | 75 | 35 | 8 |
| VA | 452 | 66 | 37 | 8 |
| NH | 163 | 60 | 3 | 1 |
| NJ | 232 | 58 | 0 | 0 |
| WA | 416 | 53 | 35 | 10 |
| MA | 342 | 53 | 4 | 1 |
| CA | 877 | 47 | 53 | 5 |
| NV | 163 | 43 | 0 | 0 |
| WV | 448 | 41 | 115 | 12 |
| MT | 214 | 41 | 16 | 4 |
| OK | 446 | 40 | 31 | 2 |
| CO | 474 | 37 | 3 | 0 |
| MO | 1,478 | 35 | 51 | 20 |
| AZ | 170 | 34 | 13 | 3 |
| RI | 95 | 34 | 46 | 21 |
| MD | 107 | 33 | 69 | 26 |
| OR | 173 | 31 | 2 | 1 |
| SD | 93 | 23 | 4 | 3 |
| ME | 79 | 22 | 0 | 0 |
| AR | 197 | 21 | 9 | 2 |
| VT | 69 | 20 | 0 | 0 |
| MI | 161 | 19 | 4 | 0 |
| CT | 282 | 17 | 16 | 2 |
| WY | 102 | 14 | 9 | 3 |
| UT | 283 | 13 | 5 | 1 |
| ND | 55 | 12 | 3 | 2 |
| FL | 104 | 11 | 54 | 5 |
| NE | 164 | 10 | 2 | 0 |
| WI | 198 | 6 | 9 | 2 |
| TN | 275 | 5 | 0 | 0 |
| IA | 95 | 5 | 7 | 0 |
| ID | 106 | 4 | 2 | 1 |
| AK | 31 | 4 | 2 | 1 |
| LA | 42 | 4 | 1 | 1 |
| DE | 57 | 3 | 4 | 0 |
| AL | 228 | 2 | 178 | 0 |
| MN | 59 | 1 | 0 | 0 |
| IL | 252 | 0 | 50 | 0 |
Every figure here comes from one public file and can be rebuilt from it. If you are writing about a specific county, the lookup above gives you its own numbers, and the inventory itself will give you the individual dams by name.
Corrections and questions: hello@beforeregret.com. If a dam is listed here whose rating or plan status has since changed, we would rather be told than not — the inventory updates and this page is a snapshot of 2026-08-28.
The full county table, 2,274 rows, one per US county with at least one dam classified high hazard potential. The same numbers as the lookup above.
high-hazard-dams-by-county.csv · the full figures as JSON
If you total the county file it comes to 16,931 high-hazard dams, not the 17,049 quoted above, and that difference is in the records rather than in the arithmetic: 37 of them are not placed in one of the 50 states, and a further 81 carry no county. Every national figure on this page counts all 17,049. The 636 dams rated poor or unsatisfactory with no emergency action plan appear as 635 in the county file for the same reason.
Every exhibit on this page as a high-contrast image, free to reuse with credit. The PNG drops straight into a document or a slide; the SVG stays sharp at any size.
Exhibit 1 (PNG) · SVG
Exhibit 2 (PNG) · SVG
Of 17,049 US dams classified high hazard potential, about one in six carries a condition rating of poor or unsatisfactory, and 636 of those have no emergency action plan on file, according to an analysis of the National Inventory of Dams by BeforeRegret.
High-Hazard Dams by County, Before Regret, 1 September 2026. Data source: USACE National Inventory of Dams. https://www.beforeregret.com/research/high-hazard-dams/
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