North Carolina Dam Hazard Classification (Class A, B, C)
North Carolina classifies dams by what happens downstream if they fail — not by how tall they are or how much they hold. The criteria are in 15A NCAC 02K .0105, and the distinction between "minor" and "serious" damage comes down to a specific number: 1.5 feet of flood rise.
The single most common error in North Carolina dam safety is assuming a small dam is a low-hazard dam. Classification is a consequence test. A six-foot farm pond dam with an occupied dwelling below it is Class C, high hazard, with everything that follows: an emergency action plan, the high-hazard inflow design flood, and the full inspection schedule.
The three classes
15A NCAC 02K .0105(a) divides dams into three classes, quoted here in full:
| Class | Hazard | Criteria as written |
|---|---|---|
| A | Low | Dams located where failure may damage uninhabited low value non-residential buildings, agricultural land, or low volume roads. |
| B | Intermediate | Dams located where failure may damage highways or secondary railroads, cause interruption of use or service of public utilities, cause minor damage to isolated homes, or cause minor damage to commercial and industrial buildings. |
| C | High | Dams located where failure will likely cause loss of life or serious damage to homes, industrial and commercial buildings, important public utilities, primary highways, or major railroads. |
What "minor damage" means — the 1.5-foot test
Class B turns entirely on the word "minor," and the rule defines it precisely. Damage is minor only when both conditions hold:
- the structures are located in back water areas not subjected to the direct path of the breach flood wave; and
- they experience no more than 1.5 feet of flood rise due to breaching above the lowest ground elevation adjacent to the outside foundation walls, or no more than 1.5 feet above the lowest floor elevation — the lower of the two elevations governing.
The rule then closes the door explicitly: "All other damage potential will be considered serious." There is no engineering judgment left in that sentence. If a structure takes more than 1.5 feet of rise, or sits in the direct path of the breach wave, the dam is Class C.
Why this drives the breach model
The rest of the rule
Subsections (b) through (f) carry requirements that are easy to miss and frequently decide a classification:
| Sub | Requirement |
|---|---|
| (b) | Classifications are proposed by the design engineer and are subject to approval by the Director. Your classification is a proposal until the Director accepts it. |
| (c) | Probable future development of the downstream area must be considered. A dam above vacant land zoned residential is not automatically Class A. |
| (d) | Dams are subject to reclassification if the Director determines hazard potential has changed. Non-structural measures of demonstrated effectiveness — flood plain zoning, early warning systems — may be considered. |
| (e) | Cascade rule. Where dams are spaced so failure of an upper dam would likely fail a lower dam, the consequence of the lower dam's failure is a determining factor for the upper dam's classification. |
| (f) | Where a bridge or roadway is the only damageable property below a dam, consideration must be given to possible loss of life, indirect economic impact through loss of service, and direct cost of damage. |
Class A / B / C versus the NID's Low / Significant / High
These are two vocabularies for the same three-tier scheme, and mixing them up causes real confusion when comparing state records against federal data:
| 15A NCAC 02K | National Inventory of Dams | FEMA P-93 |
|---|---|---|
| Class A | Low | Low |
| Class B (intermediate) | Significant | Significant |
| Class C | High | High |
History note. Statutory authority G.S. 143-215.31 and 143-215.34; rule effective June 15, 1980. The NCDEQ hazard classification criteria form reproducing this rule is revised 02/14/18.
Scope. This page is general information about North Carolina dam safety regulation, current as of 2026-08-28. It is not an engineering opinion about any specific structure and it is not legal advice. Requirements change when the General Assembly amends the Dam Safety Law or the Environmental Management Commission amends the rules — always confirm against the current text of the statute and 15A NCAC 02K, and contact the NCDEQ Dam Safety Program for a determination that binds.