USACE CWMS - Mississippi River Watershed MVR

The Corps Water Management System (CWMS) includes four interrelated models to assist with water management for the basin:

- GeoHMS (Geospatial Hydrologic Modeling Extension)
- ResSIM (Reservoir System Simulation)
- RAS (River Analysis System)
- FIA (Flood Impact Analysis)

The Mississippi River Basin is the largest river system in the United States, covering approximately 1.15 million square miles, or over 40% of the area of the Continental U.S. Several large tributary rivers flow into the Mississippi, including the Missouri, Ohio, and Arkansas Rivers. Maximum topographic relief varies from approximately 1,475 feet near the headwaters at Lake Itasca to 0 feet at the Gulf of Mexico.
The scope of this project focuses on the Upper Mississippi River (UMR) and delineation of the watershed will be the responsibility of MVP, MVR, and MVS respectively. For the most part, the modeling extents will be divided along district boundaries. However due to hydraulic complications, flood fight activities, and general operations, the area between L/D22 and L/D 24 on the Mississippi and around La Grange L/D on the Illinois will be modeled by both MVS and MVR. The Common Computation Points (CCP’s) for data hand off between districts will be L/D 10 for MVP to MVR and L/D 22 and La Grange L/D for MVR to MVS.

In the Rock Island District, the Mississippi River and its tributaries drain an area of almost 84,500 square miles, however only about 28,900 square miles will be modeled for this project. The remaining areas of the watershed (the Des Moines River basin, the Iowa and Cedar River basin, and the Illinois Waterway) have already been modeled, are in the process of being modeled, or are scheduled to be modeled next year. Most of the watershed is located within Iowa and Illinois with additional contribution areas from Minnesota, Wisconsin, and Missouri. Throughout a majority of the district, the typical floodway ranges between ½ mile to about 1½ miles and is flanked on either side by vast floodplains (up to 10 miles wide) extending to the bluffs. In most areas, a majority of the floodplain has been constricted with agricultural levees and urban development. A prime example of this constriction is located in the Quad Cities downstream of L/D 15 and another one is located just upstream of Hannibal, MO. The extensive system of levees and floodwalls in this section of the Mississippi River will make modeling difficult, especially when the full scope of flood fight activities of this region are taken into account.

From the district boundaries, the basin is roughly 315 miles long and has a maximum width of about 400 miles. The Mississippi River has a mildly sinuous channel with low banks and a small slope. During times of heavy rains, the valleys in the basin can be subjected to serious flooding as was seen in the 1993 and 2008 floods of record. The primary land use in the basin is agriculture. The largest urbanized areas in the watershed (population over 10,000), include Dubuque (IA), Clinton (IA), the Quad Cities Metro Area (IA-IL), Muscatine (IA), Burlington (IA), Fort Madison (IA), Keokuk (IA), Quincy (IL), and Hannibal (MO). There are also several other small towns located along the banks of the Mississippi River and spread along its tributaries throughout the basin.

There are 12 navigation dams located within this section of river that are operated by the Rock Island District. The primary purpose of these locks and dams is to facilitate travel and trade along the river and throughout the Midwest. The dams are primarily used to controlling the water levels during low flow conditions and have a negligible impact in providing flood damage reduction.