Answer :
River Civilization often occur in River Deltas. Deltas are a collection of the sediments the river has collected in a long span of time. This delta's are the cradle of many civilization like the Indus Valley Civilization, as well as the Egyptian Civilization. There are multiple reasons for the thriving of civilization, but primarily it is due to agriculture. River provides a natural irrigation that helps farmers grow crops more than a village needs. The surplus of goods slowly builds up and allows other occupations to rise up, with that civilizations grow.