a lot of very shallow, very salty water
A significant fraction of the valley floor, maybe 10 percent, had standing water. I made the mistake of dipping a hand with recent cuts in the water and it smarted for quite a while - it's much saltier than ocean water.
There were several kayakers out floating around on the valley floor. I waded in calf-deep, but I doubt anywhere it's more than waist deep, if that. The floor is very flat.
While I'm sure the standing water only happens in the winter, I believe the big flash floods are summer-time storms.