Oh that one is simple. Try because many human settlements were constructed next to bodies of water.
Though it’s notable that the Tibetans don’t have an indigenous flood myth, which has much to do with the fact that they live at an altitude of 10,000 feet above sea level or greater.
Though there’s a difference between flood episodes that left behind them observational evidence of their occurrence, and the fantasy “global flood” myth that the authors of your favourite mythology plagiarised from the Epic of Gilgamesh, then embellished with a raft of ridiculous fantasy extras.
Indeed, I can provide numerous cogent and consilient reasons why the fantasy “global flood”, asserted to have occured within the pages of your sad little goat herder mythology, never happened. Strap yourself in for the ride, Looby Loo, this one’s going to be a roller coaster.
[1] If the fantasy “global flood” had ever happened, then geologists would have found this out, courtesy of the existence of a single, deep, globally present sedimentary stratum dating unequivocally to a young age. This was never found. Instead, geologists found that the global map of strata was varied, with in some cases ancient strata found close to the surface, including igneous strata that should never have appeared in the fantasy “global flood” scenario.
One of those ancient strata, the Canadian Shield, being a Precambrian stratum, unequivocally dates to 1.8 billion years before present, and covers no less than 8 million square kilometres of land. Likewise, the Siberian Traps is another massive igneous rock stratum, covering 7 million square kilometres of land, which dates unequivocally to the end-Permian, 250 million years before present. The Deccan Traps in India, covering 500,000 square kilometres of land, and dating unequivocally to the late Cretaceous, around 70 million years before present, is a third example.
None of these strata would even exist, if the “global flood” bullshit was something other than the product of the televisions in the heads of mythology fanboys.
[2] Archaeologists have found ZERO evidence that several major civilisations extant at the time, ceased activity upon being purportedly drowned under 9,000 metres of water. The Ancient Egyptians and the Ancient Chinese, provide a vast body of archaeological evidence to the effect that they continued their activities unbroken, right about the time that creotard masturbation fantasists assert that they were under 9,000 metres of water.
[3] If the fantasy “global flood” had ever happened, whole swathes of aquatic life would have been exterminated. This includes tropical fish species I kept and bred successfully in the aquarium during a 35+ year career as an aquarist. The species in question would have been wiped out through osmoregulatory shock within about 72 hours, if this fairy tale had ever been real. I don’t even need to have studied fish physiology in order to know that this would have happened, but of course, the requisite scientific training helps here. ALL of the Ostariophysan fishes alone would have been exterminated, because they are ALL intolerant of salt, and something like twenty entire Orders of marine fishes, including all the reef-dwelling fishes, would have met a parallel fate. The species I’ve successfully bred in captivity have stringent water chemistry requirements, that would have been violated wholesale by the fantasy “global flood”.
Oh, and don’t try and peddle the creationist garbage that a few “kinds” somehow survived, then underwent massive speciation to produce the 33,000 species known to science, because this too is garbage. First of all, creationist liars for doctrine can’t even agree among themselves what a “kind” purportedly is, and second, among the species I’ve bred successfully is Corydoras panda, a South American catfish with tightly defined water chemistry requirements, which has a distant relative that was alive in the Eocene - the fossil of that ancestor, Corydoras revelatus, was found in 1922. That fossil wouldn’t even exist if creationist assertions about the “global flood” were something other than the products of their rectal passages.
Also part of the death toll, would have been all the higher aquatic plants, which would have been exterminated wholesale not only from osmoregulatory shock, but from being buried under millions of tons of silt, and shut off from sunlight by 9,000 metres of water. Entire phyla of freshwater and marine invertebrates would also have been exterminated for the same reasons, a particularly apposite example being the reef building corals, which not only need stringent water chemistry parameters in order to live, but also need access to light, courtesy of a symbiotic relationship with zooxanthellae (a clade of algae), which require access to light for photosynthesis if they are to remain alive.
[4] The physical and biological unreality of made up shit creationist attempts to treat science dishonestly as a branch of apologetics, to try and prop up this fairy tale, on its own tosses this vicious little exercise in psychotic fiction into the bin. Starting with Kent Hovind’s wank-break “vapour canopy” bullshit, which would have resulted in ludicrous thermodynamic exchanges, first cooling the entire planet to the ambient temperature of Pluto (around 30 Kelvins), at which point the breathable gases of the atmosphere would be liquefied or in some cases even turn into solid ices, This would then be followed by a second set of thermodynamic exchanges resulting in the ambient temperature of planet Earth rising to that of molten Copper. I’ve run the numbers on this.
Then there’s Baumgartner’s idiotic “runaway subduction” nonsense, which would have released enough heat to boil all the oceans off into space. Followed by Walt Brown’s “hydroplate” nonsense, which apart from being in direct violation of the Gas Laws, hilariously invokes a level of meteorite bombardment that would have sterilised the planet, and turned your 600 year old barge captain and his floating petting zoo into plasma. Finally, there’s the ludicrous “accelerated nuclear decay” drivel from Russell Humphreys, which would have generated enough heat to ignite helium fusion in the Earth’s core in the best case scenario, and in the worst case scenario, heated the planet to Grand Unification physics temperatures (yes, a whopping 1031 Kelvins).
[5] The exquisite sorting, in time and taxonomic order, of the fossil record, which involves sorting particles ranging from fossil pollen grains 50 microns across, to the carcasses of 100-ton Sauropod dinosaurs. The idea that this exquisite time and taxonomic sorting would have been produced by the fantasy “global flood” is manifest bullshit, especially to anyone familiar with the mathematics of fluid dynamics, and the behaviour of the Navier-Stokes equations, which describe the requisite behaviour of fluids, and which are used by Boeing and Airbus to design airliners successfully (the recent 737 Max débacle notwithstanding - though that was a software issue, not an aerodynamics issue).
The bullshit about “hydrologic sorting” peddled by professional liars for creationist doctrine, was flushed down the toilet by television footage of the 2004 Indian Ocean tsunami and the 2011 Sendai tsunami, in which the resulting turbulent water flows produced no “sorting” of any variety. Plus, the manner in which any reasonable supercomputer model using the Navier-Stokes equations would have to be tampered with to a galactically dishonest extent, in order to produce so-called “hydrologic sorting”, again flushes this fantasy down the toilet.
[6] The idea that a wooden ship twice the size of a Ticonderoga Class guided missile cruiser would be seaworthy, is a deluded fantasy, as any marine architect will tell you. The largest wooden ship ever built in recent times, was considerably smaller, and needed constant pumping to stop seawater ingress as it suffered from hogging and sagging as it traversed the waves. It’s the reason we build aircraft carriers out of high tensile strength steel alloys, not wood. That wooden ship eventually succumbed to the stresses of flexing as it traversed the waves, as documented here:
That ship fell apart in heavy seas with the loss of all hands in 1924.
Furthermore, the idea that people with Bronze Age technology were capable of building a large wooden ship is again a fantasy. Greek triremes (warships constructed from wood) wre no bigger than 120 feet, and involved a considerable investment of resources and engineering skill on the part of Greek civilisation, which was in may respects far more advanced than the collection of nomadic tribes living in the Middle East. Indeed, HMS Victory, a famous wooden warship built by the British between 1759 and 1765, was considered to be impressive because it was 186 feet long, though its structure was reinforced with metal, which almost certainly helped ensure that it was seaworthy when launched.
Indeed, HMS Victory pretty much established the maximum specifications for operational naval vessels built of wood for some time afterwards, which were only exceeded when the first ironclads were laid down. While larger wooden ships were built, these were reinforced with metal hull frames, a classic example being the American clipper ship Great Republic, which had a multiplicity of steel cross braces to ensure the structural rigidity of the hull. Every wooden ship longer than 250 feet has either failed to remain seaworthy, or needed extensive metal strructural reinforcement in order to be operational.
Quite simply, the idea that a small family of Bronze Age nomads could build a vessel twice the size of a Ticonderoga Class guided missile cruiser, is a fantasy only the truly deluded could entertain.
Oh by the way, there’s another little detail from this diseased fantasy, that contributes to its absurdity. Which centres upon Genesis 7:2, viz:
Just one teensy little problem with this passage … according to creationist orthodoxy, the fantasy “global flood” occurred sometime around 2,400 BCE. Except that, oops, the part of your mythology that defines what constitutes “clean” and “unclean” animals, namely Leviticus, wasn’t written until 1,500 years after this date. How did the captain of your fantasy floating petting zoo know the difference betwene “clean” and “unclean” animals, fully 1,500 years before this was defined?