A series of unusually cold winters in the river basin concluded in the winter of 1972-1973 , when high precipitation saturated much of the watershed , especially in the Ohio Valley and lower Mississippi Valley . This was followed by more rain in early 1973 , with river flow cresting on March 31 at Red River Landing , Louisiana , and a heavy snowmelt in the Rocky Mountains which caused western tributaries such as the Missouri and Arkansas to form a final catastrophic high in June . The flood resulted in the largest volume of water to flow down the Mississippi since the Great Mississippi Flood of 1927 . Both the Bonnet Carre Spillway and the Morganza Spillway were employed . The Bonnet Carre was fully opened between April 7 and June 14 for a record 75 days . The 1973 flood was the first time the Morganza Spillway was opened : from April 19 through June 13
Great Mississippi Flood of 1927
Great Mississippi Flood of 1927
Mississippi flood of 1973