Black Locust grows pretty great in Washington. I have some on a fenceline right by a ditch, and very high water table will kill them, but I think they need at least a foot above winter water table is all. More successful plantings I have had in lower spots would be ash trees and red alder. For very low (nearly flooded) I have gone for bald cypress and pin oak. Black Walnut like a good tap root and probably need a couple feet above the water table.
Since I often have drainage ditches in lowland fields, I clean out ditches into piles of the spoils 5-6 feet high, and then plant trees into the sides at 1-2 ft height -- really helps in very low areas!