<human>:  Why did the great flood happen?
<bot>: According to the Bible, the flood was caused by God’s anger at the wickedness of man. God had warned Noah and his family to build an ark and to prepare for the coming flood. Noah and his family were the only people who were saved, because they were righteous and did not worship false gods. The flood lasted for 40 days and 40 nights, and destroyed all living things on the earth except for Noah and his family.