How do you know the Noahic flood was falsified?
I do archaeology. I am very familiar with 4300 year old sediments.
In the western US we have cultural continuity across the 4300 time period.
We also have a mitochondrial DNA record across this time period, with no replacement by Middle Eastern DNA.
The major floods we see were in Washington state at the end of the last ice age (google "channeled scablands"). They are readily identified and dated. A global flood would have 1) been much larger and more easily discovered, and 2) eliminated evidence of the earlier flood.
Early geologists seeking to prove the flood largely gave up by about 1830.