In Montana, a small dam is a dam with a reservoir capacity under 50 acre feet at normal operating pool.  Although small dams are not required to obtain operating and construction permits from the Dam Safety Program, the concepts of dam owner responsibility still apply.

Downstream Hazard Assessment for Dams Storing less than 50 ACRE Feet

The “standard of care” nationwide is to know what happens below your dam should it fail. If your dam can store 50 acre-feet or greater, you should apply for a Downstream Hazard Classification.

What if your dam is under 50 acre feet? You still should know what hazards are at risk below your dam. It is possible to estimate the dam breach flood area using a few simplifying assumptions and making some basic calculations. For information and guidance, please refer to the Small Dam Hazard Assessment Inventory.

Repairing a Small Dam?

Please refer to this informative video with good advice.

Another valuable resources is the Small Earthen Dam Construction Guide