Was the flood an act of God's wrath?
No. The flood was not an act of God's wrath. Although God destroyed the human race in the flood, the context says it was disciplinary, not wrath. God's wrath had never yet been poured out, and the world does not know what God's wrath is.
Les explains that although God destroyed the human race in the flood, that destruction was not God's wrath; it was disciplinary. He notes God's wrath had never yet been poured out, and that God's dealings with Israel at times were also strenuous but disciplinary rather than wrath. Les adds that the world still does not know what God's wrath is, and he points to Psalm 2 as perhaps the first use of that word regarding God dealing with mankind, where after Jew and Gentile reject the Anointed One, God will finally speak in wrath, not grace or love.