When the Ganges swells, the delta becomes inundated. Also, most of the land lies below sea level. The monsoon however, does not necessarily equate to flooding. That's right, even here in the United States we have a monsoon. The southwest portion of the country experiences monsoon thunderstorms roughly from June through September.
Winds shift from a general winter direction of west or northwest to south or southeast.
Unlike the monsoon in India, torrential long lasting rains are not common. However, spectacular monsoon thunderstorms with beautiful lightning shots are very common. After all it is a season, but caused by a dominant wind I know I've spent a lot of time on the monsoon and not necessarily floods, but that's the whole point. Some people think floods and a monsoon are synonymous. Now you know, and knowing is half the battle.