Project design flood The project design flood is a hypothetical " maximum probable " flood of the Mississippi River used by the United States Army Corps of Engineers to aid in the design and execution of flood protection in the Mississippi Valley . The current project design flood was developed in 1956 by the Mississippi River Commission with input from the Weather Bureau . It is based on a scenario of three rain events in the lower Mississippi Valley occurring 3 days apart : the January 1937 ( increased by 10 % ) , January 1950 , and then the February 1938 rain event with its center adjusted to the north and rainfall pattern rotated to achieve a hypothetical worst - case flood of the tributaries of the Mississippi River . Assumptions were made based on the completion of tributary reservoirs and dams by 1960 . When the Commission reviewed the plan after the 1973 Mississippi River floods , the Project Design Flood in use was determined to be " based on sound technology that was still reliable by current standards . The project design flood peak discharges remained unchanged . " Once the project design flood was developed , flow rates at critical points are used to determine how high levee s need to be , how deep the dredging needs to be , and the flowrates at which flood control structures need to be used . 1928 project design flood . In response to the Great Mississippi Flood of 1927 , the Flood Control Act of 1928 authorized the Mississippi River and Tributaries Project ( MR & T ) , which is implemented by the Mississippi River Commission ( MRC ) . The MRC estimated a maximum probably flood discharge of at Cairo , Illinois that was greater than the 1927 flood but less than the 1927 flood combined with the maximum recorded discharge of the Ohio River in 1913 . In a separate analysis , the U . S . Weather Bureau determined that a " maximum possible " flood would result in a discharge of based on the maximum recorded flows of the upper Mississippi , Ohio , Cumberland , and Tennessee Rivers . In a combined analysis , the higher flow rate estimate was used . Adding the flows of the Arkansas and White River s , the maximum flow farther downriver at Arkansas City , Arkansas was estimated to be with a flood stage of . Adding the flows of the Yazoo and Red River s , the Weather Bureau estimated a flow of just North of Baton Rouge at Red River Landing , Louisiana . 1941 project design flood . The Ohio River flood of 1937 caused the flood stage at Cairo to reach despite a flow of only . In response , the United States Congress ordered the MR & T to review of the flood control plan . Maximum flows were changed to at Cairo , at Arkansas City with the White River backwater area levee overtopped , and Red River Landing unchanged at . Current project design flood . The current project design flood was developed at the request of the Senate Public Works Committee in 1954 . The Mississippi River Commission and the Weather Bureau worked together to investigate hypothetical flood conditions . The study of a set of 35 combinations of actual storms resulted in the selection of combination called " Hypo - Flood 58A , " a combination of previous storms in 1937 , 1938 , and 1950 . The peak discharges were found to be at Cairo , at Arkansas City , and at Red River Landing . After the 1973 Mississippi River floods , the MRC reviewed the project design flood and found that it was still reliable based on current standards .