"the primary purpose of these floating gardens is to
(1)increase regional food supplies
(2)provide more goods for export
(3)serve as an island bridge to the mainland
(4)expand recreational areas for children
"

The floating gardens primary purpose of the  Gaibandha district was to increase the regional food supplies. The land during the monsoon season would be flooded and no way for the people to grow crops. This helped them to have food. These floating gardens were made to provide food for the poorest people of Bangladesh.