Dams in Idaho
Idaho has 406 dams in the National Inventory of Dams, of which 106 are classified high hazard — and only 1.9% lack an emergency action plan, one of the better records nationally. Inventory, condition and hazard data computed from the USACE extract stamped 2026-8-28, with the governing law cited below.
Verified inventory data and a pointer to where Idaho's dam safety law lives. It deliberately does not summarise what that law requires — those requirements have not been checked against current primary sources for Idaho, and a stale paraphrase of a dam safety statute is worse than none.
For a state written up in full, see North Carolina.
Idaho by the numbers
| Measure | Count | National rank |
|---|---|---|
| Total dams | 406 | 44th |
| High hazard | 106 | 38th |
| — with an EAP recorded | 104 | |
| — with no EAP recorded | 2 | 42nd largest gap |
| — EAP not required | 0 | |
| High hazard rated Poor | 2 | |
| High hazard rated Unsatisfactory | 2 |
4 of Idaho's high-hazard dams are rated Poor or Unsatisfactory (3.8% of them).
Governing law
The Idaho dam safety statutes are enumerated in the Idaho Code Section 42-1709 through 42-1721 (IC §§ 42- 1710 § 42-1720). The regulations are contained in the Idaho Administrative Rules, Rules 37.03.05 37.03.06 (IDAPA r.
Citation compiled from the ASDSO 2020 summary of state dam safety laws and checked to refer to Idaho. It tells you where the law lives, not what it currently says: statutes get amended and section numbers get renumbered. Read the current text before relying on it, and contact the Idaho dam safety program for a determination that binds.
Counties with the most dams
| County | Dams | High hazard | Poor/Unsat. |
|---|---|---|---|
| Owyhee | 50 | 4 | 10 |
| Valley | 41 | 4 | 2 |
| Washington | 24 | 5 | 0 |
| Franklin | 21 | 8 | 2 |
| Caribou | 20 | 8 | 0 |
| Twin Falls | 19 | 5 | 0 |
| Elmore | 18 | 3 | 2 |
| Fremont | 16 | 4 | 1 |
| Ada | 16 | 4 | 2 |
| Custer | 15 | 2 | 4 |
| Bonneville | 15 | 6 | 0 |
| Lemhi | 13 | 0 | 4 |
Where to go for Idaho's requirements
This page does not summarise what Idaho law requires. These do, or will point you at someone who can:
- ASDSO — Idaho dam safety programme. The Association of State Dam Safety Officials maintains a page per state with the programme contact. Start here if you need to reach a regulator.
- National Inventory of Dams. Search by state or county for an individual dam's record — the source of every figure on this page.
- FEMA National Dam Safety Program. Federal guidance that underpins most state schemes, including P-93 on hazard classification and P-94 on selecting design floods.
- How four neighbouring states differ. North Carolina, South Carolina, Georgia and Virginia compared on permit thresholds, classification and emergency action plans — useful for calibrating what to expect from any state programme.
How Idaho compares
Nationally, 2,476 of 17,049 high-hazard dams have no emergency action plan on record. Idaho accounts for 0.1% of that gap. Full rankings, method and the downloadable dataset are on the national EAP gap page.
Data source. Computed from the U.S. Army Corps of Engineers National Inventory of Dams national extract, stamped 2026-8-28. NID reflects what state and federal programs have reported to USACE; an "EAP Prepared: No" flag means no plan is recorded rather than proof that none exists.