| Flood Impacts |
| 34.0 | This is the top of the Hannibal Floodwall. |
| 31.8 | This is the RECORD FLOOD LEVEL that was reached on July 15 1993. |
| 31.0 | This level is expected to be met or exceeded on average once every 500 years. |
| 29.6 | This level is expected to be met or exceeded on average once every 200 years. |
| 28.6 | This is the flood level that was reached on April 25 1973. |
| 28.2 | The Fabius River levee (Right Bank) is overtopped between River Mile 332.4 and 323.5, flooding 14,200 acres. The Marion County levee is overtopped between River Mile 320.7 and 323.5, flooding 4000 acres. |
| 28.0 | The elevated boat club, outside the levee, floods. This level is expected to be met or exceeded on average once every 100 years. |
| 27.8 | The Sny Island and South Quincy levees are overtopped between River Mile 315.4 and 264.3, flooding 110,000 acres. The South River levee is overtopped between River Mile 320.5 and 312.1, flooding 10,000 acres. |
| 27.5 | The South Quincy Levee (Left Bank) is overtopped between river miles 325.4 and 317.8, flooding 5500 acres. |
| 27.0 | A few small bussinesses along the riverfront outside of the floodwall, along Bear Creek and along the minnow branch of Bear Creek are either cut-off or inundated. A large portion of downtown Hannibal is cut-off. |
| 26.2 | The Sny Island Drainage District Levee is overtopped. |
| 26.1 | This level is expected to be met or exceeded on average once every 50 years. |
| 25.3 | This flood level was reached on October 4 1986. |
| 24.0 | Highway 79, south of Hannibal, floods. |
| 23.9 | This level is expected to be met or exceeded on average once every 25 years. |
| 23.0 | Area south of Collier Street and East Side of Sycamore Street outside the Hannibal flood wall floods. |
| 22.5 | The Norfolk Southern Railroad tracks running east and west flood. |
| 22.0 | Major flooding begins. |
| 21.5 | This level is expected to be met or exceeded on average once every 10 years. Additional Flood Gates at Broadway Ave, and Main Street are installed. |
| 20.5 | The Burlington Northern/Sante Fe railroad tracks running North and South and the railroad yards begin to flood. |
| 19.5 | The Hill Street and Center Street flood gates are installed. |
| 19.2 | This level is expected to be met or exceeded on average once every 5 years. |
| 19.0 | The Corps of Engineers begins flood fight proceedures. |
| 18.0 | Moderate flooding begins. Two floodgates are installed. Gate wells are shut down to prevent the sewers from backing up. Also at this level pumps are set to standby. |
| 17.0 | Riverside Parks on east side (inside the Illinois Sny Levee) floods. |
| 16.5 | This level is expected to be met or exceeded on average once every 2 years. |
| 16.0 | Flood Stage. Damage begins to buildings in unprotected low areas. Minor flooding begins. |
| 13.0 | A few unprotected low lands begin to flood. |
