This is a shot of the dam showing the relatively small openings and why the water 'gushes' out. I read today the dam is designed to withstand a 1 in 5000 year flood. Personally, I doubt the structure will be there in 4,550 years, but I guess you never know! http://en.wikipedia.org/wiki/Scrivener_Dam
A 'slow' shutter speed blurs the water surface, which meant that HDR could be used this time! :)