https://www.sierraclub.org/missouri/blog/2013/06/causes-taum-sauk-reservoir-breachAn interesting read, and a few similarities with our dams. Steepness of outboard slope, sand filled, long history of leakage. etc.
In the following report from the ASDSO, they state,
Contributors to Failure
Traditionally, it has commonly been assumed that safety is the default for dams and other systems, and that failures are therefore due to atypical physical factors (eg, ‘Acts of God’) and/or egregious ‘human errors’. However, research over the past few decades suggests that this paradigm should be reversed, with the new default view being that a natural tendency is for systems to move towards disorder and failure (in line with the concept of increasing entropy), and with continual human effort thus being needed to maintain order and prevent failure.