Is interpreting Noah's flood as a civilization-wide event compatible with Roman Catholicism?

The Catechism divides Scripture, according to intent of the writers, in the following ways:

115 According to an ancient tradition, one can distinguish between two senses of Scripture: the literal and the spiritual, the latter being subdivided into the allegorical, moral and anagogical senses. The profound concordance of the four senses guarantees all its richness to the living reading of Scripture in the Church.

116 The literal sense is the meaning conveyed by the words of Scripture and discovered by exegesis, following the rules of sound interpretation: "All other senses of Sacred Scripture are based on the literal."

117 The spiritual sense. Thanks to the unity of God's plan, not only the text of Scripture but also the realities and events about which it speaks can be signs.

1. The allegorical sense. We can acquire a more profound understanding of events by recognizing their significance in Christ; thus the crossing of the Red Sea is a sign or type of Christ's victory and also of Christian Baptism.

2. The moral sense. The events reported in Scripture ought to lead us to act justly. As St. Paul says, they were written "for our instruction".

3. The anagogical sense (Greek: anagoge, "leading"). We can view realities and events in terms of their eternal significance, leading us toward our true homeland: thus the Church on earth is a sign of the heavenly Jerusalem.

118 A medieval couplet summarizes the significance of the four senses:

The Letter speaks of deeds; Allegory to faith; The Moral how to act; Anagogy our destiny.

As to the specific intention of the story of the flood, and thus the mode of interpretation under which the story would fall, like most other accounts of specific descriptions and verses in the bible, there is no 'official' doctrine regarding such matters. What is ascertained is that in any case the stories and the details as they were intended to be are true in such capacities. This means that in any one of the previous ways one wishes to interpret the flood story, it must in any way be true, rather than partially true or false.

Much of the beginnings of Genesis have been traditionally allegorically interpreted. To name only one example, St. Augustine thought of the 'light' that God made and divided from the 'darkness' could be meaningfully interpreted as the creation of angels. The allegorical approach to Genesis has the benefit of avoiding some problems that come with the more literal interpretations seen in many Protestant groups (which invariably leads to conflict between what appear to be inherent contradictions, and contradictions in science). But what is more important is that this approach also seems to garner greater meaning. Instead of being concerned with the literalness of whether God created the stars before 'light' or 'light' before the stars, we can focus more so on the meaning of these events, not simply as events in themselves but as potential symbols or phrases that carry greater theological weight. At the same time, the nature of the interpretation in such matters is existentially neutral to the fact of its existence. So whether or not the flood truly occurred, as in a sequence of events, need not deter our understanding of the story's meaning in an allegorical interpretation. This applies to all modes of interpretation. The Church is clear however that there are specific cases (the New Testament for example) in which our mode of interpretation must necessarily include the literalness of the specific events described. This also applies to the monogenism present in the Adam and Eve story, where the Church states it is necessary to recognize all human life essentially originates in its nature in two persons, who were created with original justice but who fell into sin, and who thereafter transposed such a fallen nature to mankind.

Thus, to answer more specifically the question, as to whether or not your specific understanding of the flood is aligned with the Catholic Church's stance on the story is somewhat of an arbitrary desire (though by no means unwarranted). The answer is that there isn't necessarily an answer. At most we can state that your interpretation must not deny the essential truth of the story, which is that God is both merciful and just, and enacts both essences in the deprived and sinful state of humanity. Furthermore, your interpretation must not deny that God speaks and breathes in His human creation through a covenant language, in which He is perfectly loving and just. These are the essential and primary purposes for which the story has been written, and as such it is these details that must not be left to individual interpretation, lest the perfect spiritual wisdom of Scripture be tainted by individual failures. In any such case of interpreting Scripture, the essential meaning and primary purpose of such Scriptures must be referred to the Church's Apostolic ministry for greater wisdom and authority, be such wisdom found in the present members or members of the past (there is a reason St. Augustine is so popular, and it's not due only to his cool name). And it is under canon law and the living Spirit that such ministers must be guided into wisdom.