Mike -
It was my understanding that the flow last October was the highest since first of the dams had put in place.

I believe that the high flows from more than a century ago are based on flood or scour marks on the canyon walls there at the Dalles and calucations of what flows it took to create those marks - the dates based on ages of the trees.

The dams do provide some protection by storing some of the flood waters. Using the flood of last October as a base - if that rain event had lasted even a 1/2 day longer, or there were lots of snow on the ground or it was one of several closely spaced events (occurring prior to the dam operators having a chance to release the stored water caught in an earlier event) they would provide only limited protection from those really large events. Given the history of the area it is not a question of if that type of flood (200,000 t0o 500,000 cfs - last October was 166,000) will occur again but rather than when. Hopefully it will not be in our life times but who knows.

Tight lines
S malma