The primary cause of floods in Assam is:

The primary cause of floods in Assam is heavy monsoon rainfall. The monsoon is a seasonal wind pattern that brings heavy rains to South Asia. In Assam, the monsoon season typically runs from June to September. During this time, the Brahmaputra River and its tributaries swell with water, often overflowing their banks and inundating large areas of land.

Tsunamis are large waves caused by earthquakes or volcanic eruptions. They are not a major cause of floods in Assam. Earthquakes are also not a major cause of floods in Assam. Glacial melt is the melting of glaciers, which can cause flooding in some areas. However, it is not a major cause of floods in Assam.

In conclusion, the primary cause of floods in Assam is heavy monsoon rainfall.