I stumbled upon this summary of the Mojave flood myth:
Many years ago, people lived under the ground. There came a time when there was no food, when the people sent a humming-bird up to see what he could find for them to eat. He saw the deep roots of a grapevine, which he followed up to the surface of the earth. The people went up through the hole and began living above ground.
One day a man looked down into the hole made by the vine, through which the people had entered the upper world, and saw that water was rising up through it. The wise ones knew that a great flood was coming and that something had to be done to save humankind.
They then cut down a great tree and hollowed it out to make a canoe, placing a young girl in it. The tree-trunk canoe floated high on the waters until nothing but water could be seen in any direction The wise ones had warned the girl not to leave the vessel until it touched land, even if she heard the waters going down.
Finally, the tree-trunk canoe touched ground. When the girl emerged, all the world had been drowned. She wondered whether she would always be alone. She went up to the mountains to rest. As she lay down, the sun shone on her, warming water that dripped down on her body from the rocks. This magic water impregnated her and she later gave birth to a daughter who conceived in the same way. All of us are descended from her.
I wonder what caused the waters to rise. Is there a version of the myth that explains why the flood happened?