I've gotten questions about whether private dams are more likely to fail than publicly owned ones. Being a scientist, I wanted some numbers. This is what I found.

56.4% of dams are privately owned. https://twitter.com/dustinpwalsh/status/1263140689707249664?s=20

Between January 1, 2015 and December 31, 2019, the ASDSO dam incident database records 165 dam failures.

Of these, 124 were privately owned dams. That's 75% of failures.

So in terms of % of failures vs. % of dams, private dams are an outsized problem.

Most of the dams that failed had a fairly small reservoir capacity. Only 11 of the 165 failed dams stored >1000 acre-feet. Of those 11, 7 of them were private. So even though many private dams are small, they still have an outsized footprint for larger dam failures.

But the largest dam (in terms of reservoir capacity) to fail in the 5 years I looked at was the Spencer Dam, in Nebraska, that failed and caused devastating flooding in March 2019. It was owned by a utility. https://www.enr.com/articles/49242-spencer-dam-failure-report-utilities-dam-owners-must-prepare-better-for-ice-runs-in-northern-dams

Here's the ASDSO incidents database if you want to do some more playing: https://damsafety.org/incidents