Child’s body discovered from sewerage drain after 68 hours

A body of a child, Kamal Uddin, was discovered in Chittagong, 68 hours after he fell in a sewage drain. The first two days were spent searching the Chasma canal and drains connected to it but there were no signs of the child. His body was discovered from Mirza canal of Muradpur, Chittagong.

How did an open canal turn into a death-trap? Why are these open drains not being covered even after several deaths?