The process responsible for the formation of delta at a place where rivers meet the sea is 

1.  Emulsification

2.  Colloid formation

3.  Coagulation

4.  Peptisation

HINT: It is because of coagulation.

Explanation: River water is a colloidal solution of clay and sea. Water contains various electrolytes. When river water comes in contact with sea water, then the electrolytes present in sea water coagulate the suspended colloidal particles which ultimately settle down at the point of contact.