[cc438]

That number is nowhere near accurate as we learned during the South Carolina floods back in October. The state estimates there are between 10,000 and 20,000 unregulated dams in South Carolina alone: http://www.thestate.com/news/local/article41315256.html

Those are the dams that pose the greatest threat. You can't plan for something you don't know about and the threat posed by such an extensive system of "invisible" dams is immense. A small earthen dam on a farm may not pose much of a threat by itself but its failure can cause a cascade of failures further downstream if it breaks when those dams are already at their limit.

[jameshart]

So, in South Carolina, The State reports that the state estimates that there are between 10,000 and 20,000 dams in the state which are not regulated by the state.

You'd think that a publication called 'The State' would be a lot more careful about throwing that term around, but within that article, it talks about "the state" meaning South Carolina as a geographical area, "the state" meaning the SC government as a regulatory authority, "the state" meaning government actors in general, and "the state" as a newspaper (though they do refer to themselves as "The State newspaper". Presumably they aren't claiming to be the official state newspaper, just a newspaper called 'The State').