Actually, he said the Gibraltar waterfall event took place 5 million years ago. Interestingly enough, one of the more odd German plans for the postwar (had the Nazis won) was a hydroelectric project / bridge across the strait, to harness the slight current (I dunno if it goes in or out, but I suspect it's out). Another was to create a huge artificial lake (the old geography of Lake Tritonis, give or take) in order to irrigate the Sahara. ;'D
Ryan's work came from the engineering studies made by the Soviets leading up to the construction of the Aswan High Dam. That's described though in one of the early chapters of Noah's Flood. :')
Yup. I have it but it's been a while since I read it. There's also a one hour TV documentary.
I don't remember that this event/effect was dated. (I'll look back through the book later)