A low-head dam in Hochatown, Okla. At a similar low-head dam on the Elk River in Noel, Mo., a man died over the weekend after becoming trapped in the dam’s hydraulics while trying to save a boater.

In recent weeks, visitors have been constructing dams at Big Rock, situated in Beargrass Creek between Cherokee Park and Seneca Park, in an effort to form makeshift pools for recreational swimming ...