Were the flood and God's dealings with Israel expressions of His wrath?
No. The flood and God's strenuous dealings with Israel were not expressions of His wrath; they were disciplinary acts. God's wrath had not yet been poured out on mankind, and the world still does not know what the wrath of God is.
Les teaches that even though God destroyed the human race in the flood and dealt with Israel at times in rather strenuous ways, it was not God's wrath; it was disciplinary. He explains that God's wrath has never yet been poured out, and so far as the wrath of God is concerned, the world does not know what it is. In Psalm 2, after Jew and Gentile reject the Anointed One and are brought to derision and complete confusion, God says He will speak to them in His wrath—not in grace, not in love. That is the first place the word is used regarding God dealing with mankind, contrasting with His earlier disciplinary dealings.