There is a post in the Mississippi river walleye forum with tips on fishing high water. Those fish have to eat. If they dont they would of starved to death long ago.
Try looking for shoreline current seams. Those fish can be right on the bank. Not un common to pitch a jig on shore and drag it back into the water in some spots. It may take some time searching out the right seams but keep looking.
Back water areas and below islands offer areas with less flow and sometimes cleaner water. Even in the highest water there is always a place with less flow. Many times you can still find a spot where 1/4 ounce jigs or less are plenty for pitching. Find a larger area with less flow and cleaner water try trolling cranks.
Another area I like to look is fast water with lots of current breaks on it. It doesnt take much for a walleye to hid out of the current. A stick, rock, dip in the bottom will all work just fine. Rip rap shoreline is a perfect example of this. It offer tons of current breaks. Side channels with hard bottom and logs work well to. One spot I used to love up here on pool 2 in high water was a little side channel that brushed up against a rocky shoreline where many trees had fallen in. Fast current going though this little area but it held fish like crazy. 3′ to 5′ depth and maybe 50′ wide.
Hope that helps a bit.