Does excessive rainfall cause flood

Yes, excessive rainfall can cause flooding. The water has to go somewhere, and if the rainstorm is widespread enough and long enough, the water may overflow the river channel and flood wide areas. In his book "Life on the Mississippi", Mark Twain described sailing his steamboat across large areas of Mississippi farmland to rescue stranded people.

Almost every year, the rains and snowmelt in the northern midwest cause floods on the Red River in North Dakota.