I'm looking more at surface evidence like scablands from rushing water, the Columbia River Gorge type if geology, erosion of hills which have a distinct rushing water type of geology, giant current ripples, water level flood marks on hills and mountains, locations, and size as well as types of loads of flood sediments left behind, source of flood water, those types of visible evidence.
The Ice Age Flood happened 12,000 years ago and there is still lots of visible evidence everywhere. If, and that's a pretty big "IF", a Global flood actually happened a mere 4000 years ago, all of the Ice Age flood evidence would all be washed away by the imagined proceding world wide flood. Not only that, but we would see clear evidance of that flood everywhere we looked. There's no way to visibally hide a water event that huge and angery.
Washington scablands after Ice Age Floods:
Channeled Scablands
Video of ripples left behind from Ice Age Flood:
Columbia River Gorge:
https://www.fs.usda.gov/recmain/crgnsa/recreation