G.K. Chesterton does not address the flood stories as far as I know, but he does address the story of the Garden of Eden in his book, The Thing in the chapter called “The Outline of the Fall.” Here are his thoughts. I’m including my comments in brackets:
When a man is as great a genius as Mr. [H.G.] Wells, I admit it sounds provocative to call him provincial. But if he wants to know why anybody does it, it will be enough to point silently to the headline of one of his pages, which runs: "Where is the Garden of Eden?" To come down to a thing like that, and to think it telling, when talking to an intelligent Catholic about the Fall, that IS provinciality; proud and priceless provinciality. The French peasants of whom Mr. Wells speaks are not in that sense provincial. As Mr. Wells says, they do not know anything about Darwin and Evolution. They do not know and they do not care. That is where they are much better philosophers than Mr. Wells. They hold the philosophy of the Fall, in the form of a simple story which may be historic or symbolic, but anyhow cannot be more important than what it symbolises. In comparison with that truth, it does not matter twopence whether any evolutionary theory is true or not. Whether or no the garden was an allegory, the truth itself can be very well allegorised as a garden. And the point of it is that Man, whatever else he is, is certainly NOT merely one of the plants of the garden that has plucked its roots out of the soil and walked about with them like legs, or on the principle of a double dahlia has grown duplicate eyes and ears. He is something else, something strange and solitary; and more like the statue that was once the god of the garden; but the statue has fallen from its pedestal and lies broken among the plants and weeds. [My emphasis] This conception has nothing to do with materialism as it refers to materials. The image might be made of wood [rather than pre-human primates]; the wood might have come from the garden; the sculptor[God] presumably might, and probably did, allow for the growth and grain of the wood in what he carved and expressed [thus allowing for the possibility of some sort of pre-human evolution, as Pius XII allowed for in Humani Generis (1950)] . But my fable fixes the two truths of the true scripture. The first is that the wood [pre-human body that became human] was graven or stamped with an image, deliberately, and from the outside; in this case the image of God [the human, spiritual soul expressed in the body]. The second is that this image has been damaged and defaced [The Fall, no matter how it actually occurred], so that it [the statue of the god—human nature] is now both better and worse than the mere plants in the garden, which are perfect according to their own plan. There is room for any amount of speculation about the history of the tree before it was turned into an image [ideas of evolution or not]; there is room for any amount of doubt and mystery about what really happened when it was turned into an image [God breathing into the clay? Other means?]; there is room for any amount of hope and imagination about what it will look like when it is really mended and made into the perfect statue we have never seen. But it has the two fixed points, that man was uplifted at the first and fell; and to answer it by saying, "Where is the Garden of Eden?" is like answering a philosophical Buddhist by saying, "When were you last a donkey? [referring to the idea of reincarnation current in Buddhism]"You can read the entire Chapter (31) here.