Actually, here in the east a lot of the whitewater opportunities we have are the result of dam releases. In one case there was actually some opposition from the whitewater community when FERC ordered one hydro dam to release at "run of river". This prevented them from doing a pond and release flow schedule, which killed a lot of the whitewater on that river. Since we're dependent on rain rather than snowmelt, dams can be an asset in some cases in this area.
There are a lot of "flood control" projects in the middle of nowhere, with absolutely no water behind them, that leave you scratching your head. Keeping the Corps busy I guess as has been pointed out.