Genesis 8:11

And the dove came to him at the evening time, and, behold, a leaf of olive gathered, broken off, she brought in her mouth, and which she had taken from the Mount of the Meshiha. And Noah understood that the waters had lightened from being on the earth.

AND LO AN OLIVE LEAF. From the plain meaning of this verse it would appear that the trees were not uprooted or blotted out in the flood because there was there no flooding stream since the whole world became full of water. But in Bereshith Rabbah the Rabbis have said, “From where did the dove bring the olive leaf? Rabbi Levi said, ‘She brought it from the Mount of Olives since the land of Israel was not inundated by the waters of the flood. This is as the Holy One, blessed be He, said to the prophet Ezekiel: Son of man, say unto her: Thou art a land that is not cleansed, nor rained upon in the day of indignation.’ Rabbi Biryei said, ‘The gates of the garden of Eden were opened for the dove and from there she brought the leaf.’” Thus the intent of the Rabbis is that the trees were uprooted and blotted out in those places where the flood was, and surely the leaf faded. Similarly the Rabbis said, “Even the [solid substance of the] lower stationery millstone was blotted out in the flood,” and [to substantiate this statement] they expounded the verse, The waters wore the stones, [as referring to the waters of the flood which wore down stones]. And their saying that “the Land of Israel was not inundated by the flood” is to be understood as meaning that the rain of the flood was not there, as it is written, nor rained upon; the fountains of the great deep were not therein. But the waters did spread over the whole world, and all the high mountains that were under the whole heaven were covered,, 19. as it is clearly written, and there is no partition around the Land of Israel to prevent the waters from entering. And so did the Sages say in Pirkei d’Rabbi Eliezer: “The waters of the flood did not come down from heaven upon the land of Israel, but they rolled in from other lands and came there, as it is said, Son of man, say unto her, etc.” Now according to the opinion of Rabbi Levi, [mentioned above, that the dove brought the olive leaf from the Mount of Olives], it was because the torrential rain did not come down upon the land of Israel and the windows of heaven were not opened there that the trees remained there while in the rest of the world they were broken and uprooted by the flood and His mighty rain.
But I wonder about their saying that [the olive leaf was brought by the dove] from the garden of Eden. If it were so, then Noah did not know that the waters abated from off the earth for there [in Eden] the waters of the flood did not enter. But perhaps its gates were closed so that the waters did not enter there, but when the waters abated they were opened. [Thus the olive leaf indicated the opening of the gates which in turn indicated that the waters had abated.]
It is on the basis of this opinion of theirs [—that the trees were broken and uprooted in the entire world during the flood — that the Rabbis] have said there in Bereshith Rabbah, “And he [Noah] planted a vineyard. And from where did he have a branch? Said Rabbi Abba bar Kahana, ‘When he went into the ark he had taken with him branches of the vine, shoots of fig trees, and stumps of olive trees.’”

ותבא...לעת ערב, it came (back) at evening time of the same day it had been dispatched.

טרף, both vowels in this word are kametz, indicating that the word is an adjective similar to having been spelled טרוף, as a participle. The word implies that the pigeon had torn this leaf off an olive tree with its beak in order to bring it back to Noach. This is the reason why the Torah used the word טרף, to show that Noach realised that it had torn it off the tree and broken it from the olive. [not just from a branch. Ed.] This was not a leaf which had been found floating on the surface of the water.

כי קלו המים, that they had decreased in quantity. When something is in short supply it is often referred to as being קל, whereas when something is in ample supply it is called כבד. Examples of this are found in Job 14,21 יכבדו בניו,”his sons become ‘heavyweights’ (important, of consequence) We have the expression מקנה כבד, a great deal of cattle (Exodus 12,38) or חיל כבד, an army of numerous soldiers (Kings II 18,17). Why did the pigeon choose a leaf from an olive tree? Perhaps it was the first tree it encountered after flying away from the ark. Or, seeing that the leaves of the olive tree stay on the tree all year round it was the most likely leaf available. According to Sanhedrin 108 the pigeon reasoned that even a bitter tasting leaf eaten in freedom was preferable to being cooped up in luxurious surroundings. In the final analysis, the pigeon preferred to entrust its future to G’d rather than to man.

והנה עלי זית טרף בפיה, “and behold, it had a sprouting olive leaf in its beak.” The word טרף in this sense also occurs in Ezekiel 17,9 i.e. כל טרפי צמחה תיבש, “all its sprouting leaves may wither.” [The normal translation of the word טרף is familiar to us from Genesis 37,33, where Yaakov used it when confronted with the bloodied shreds of his son Joseph, is “torn.” Presumably, the author felt that if that was the meaning of the word here, it would have been unnecessary, as how else could the pigeon have gotten hold of it. Ed.] Seeing the sprouting leaf, Noach knew that the waters had receded significantly. It was also clear to him that the pigeon had not found that leaf floating on top of the water. He was certain that it had been plucked from a tree that was in good condition.