Can the Flood actually be disproved, or is it just generally accepted scientific reasoning?
In the sciences, your hypothesis needs evidence to support it along with being potentially falsifiable via testing (if X occurred, then you'd expect to find Y). Otherwise there's no reason to accept it, even if there are no other candidate explanations.
In the case of the Noachian flood, much of the early history of geology involved individuals trying to find evidence that earth's landscapes and geologic strata were the result of such an event. This was the underlying assumption that geology worked on the pretty much all of the 18th century and the early part of the 19th.
However, as research continued, it became apparent that there evidence presented by nature didn't support a single, massive event shaping the surface of the earth and the geological column. The Noachian Flood became untenable as a hypothesis sometime around the 1830s/1840s because the evidence being found didn't support it, and other hypotheses had better support.
There were a range of competing theories that began to be developed over the second half of the 18th century to try and better explain what was being observed. Neptunism, plutonism, gradualism, catastrophism, diluvialsim, gap creationism, glaciation and so on. Some of these were efforts to keep God's end in (so to speak), but even these were progressively abandoned by academic/professional geologists through the latter half of the 19th century.
However, it's important to remember that there remained a strong overlap between religion and the sciences during the first half of the 19th century. So the 'naturalist clergy' and 'scriptural geologists' (religious ministers with some scientific credentials) made a real push in the 1820s through 1830s to try and resurrect a literalist view. By the 1850s though, this had been pretty much abandoned, even in the popular scientific press of the time.