Emergency landing theoretical

Question for you guys:

I fly out of Troutdale, Oregon (KTTD) which is at the mouth of the Columbia
River Gorge. Because of sheer cliffs, tunnels, things like that, if I had
to make an emergency landing in a single engine aircraft, in some stretches
it would be treacherous or impossible to land on the road.

As a boater, however, I'm familiar with the river charts and know that much
of it is only 2 to 4 feet deep. So if I knew, reasonably, that I could
ditch very shallow water, would that be a viable emergency landing plan as
opposed to a winding and potentially busy freeway with a 700' cliff on one
side?

Different in high wing verses low wing?

-c