If the Lord (or was it God? See the Two Flood Stories commentary) really did tell the Noah's Ark story to the Genesis writer, rather than the flood story merely having sprung from the imagination of the ancients, then he either spoke falsely, or else he is indeed an extremely whimsical god, cruel to animals and the most enviromentally destructive agent the world has ever known.

Here is the story, as recorded in the King James Bible:

An Angry God Orders Noah to Build an Ark

Speaking to Noah--who was to be spared by the Lord, he said,

"Make thee an ark...and thou shalt come into the ark..and thy sons, and thy wife, and they sons' wives with thee. And of every living thing of all flesh, two of every sort shalt thou bring into the ark...they shall be male and female" (Genesis 6:14-19).

Thus, to populate his new earth, the Lord foresightedly commanded that one male and one female of each species be included on the ark. Noah did as he was told:  

"And Noah did according unto all that the Lord commanded him...Of clean beasts...there went in two and two...the male and the female."
(Genesis 7:5-9)

What God Did Next Made No Sense

Then the flood came which destroyed every living thing which was not in the Ark:  

"And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark." (Genesis 7:23).

Now, it is hard enough to understand why the disappointed Lord could not have just waved his hand to make the necessary improvements in existing man instead of killing every human being on earth, but nearly incomprehensible is the Lord's decision to drown the whole planet, destroying "every living substance". After all, the Lord spent the entire third day of creation making the grasses, herbs, and fruit bearing trees (Genesis 1:11-13), and the fifth day making animals (Genesis 1:20-23); why would his anger at man lead him throw all this other good work down the drain? Couldn't the omniscient God think of a way to kill man without wastefully killing the grass and animals, too? The grass hadn't offended God, and the animals hadn't done anything wrong, had they?

Which is more likely? God actually did this, or the flood story (actually, stories) is based on an actual flood that covered a large part of the ground in which ancients Israelites lived, but grew into a flood of biblical proportions as the flood story was told and retold, and embellished, over time? If not the latter, then alternative is to believe that God wasted several days of creation. Why couldn't he just have killed those men and women who angered him, and not all the rest, plus the animals and the plants? Or, since he was allegedly all-powerful, why couldn't he just have snapped his fingers and caused the DNA in all humans to instantly program human behavior to exactly what he wanted? He had the power to do that, so why didn't he do it, if he existed?