20th Century Stage Trends Along the Mississippi River

Abstract

River regulation has systematically increased along much of the Mississippi River throughout the 20th century. There is only a cursory understanding of changing hydrological processes along the entire length of the Mississippi River over this same time period. This study compared four measures of river hydrology, at the beginning and at the end of the 20th century . River-stage data were statistically analyzed from 15 equidistant gauges along the main stem of the Mississippi River. The findings revealed (1) significant changes in components of river hydrology between both time periods and (2) varying patterns of change between the different river segments. The Upper Mississippi River (UMR) experienced significant increases in peak, mean, and minimum monthly stages between the periods, while variance of these same stage conditions declined. The Middle Mississippi River (MMR) exhibited significant increases in the magnitude and variance of river stages. The frequency and duration of flood stages increased between the two periods on the MMR. The Lower Mississippi River (LMR) demonstrated a mixed response during this time period. Gauges at the upper and lower end of the LMR changed similarly to the gauges on the UMR. However, gauges on the central part of the LMR showed decreases in peak, mean, and minimum river stages. [Key words: engineered features, hydrology, Mississippi River, river stage.]

The Mississippi River source-to-sink system: Perspectives on tectonic, climatic, and anthropogenic influences, Miocene to Anthropocene

“…Decreases in bed elevation are attributed to bed scour below Gavins Point Dam, as well as channelization of the lower Missouri River. Discharge-specific stage increases of > 3 m are documented in various parts of the Mississippi main stem, from Minnesota to Louisiana (Wasklewicz et al, 2004;Remo et al, 2009). The US-ACE has recognized and addressed this problem by increasing the height (and breadth) of main-stem levees, beginning in 1897 (4m), then in 1928 (7m), 1972 (9 m), and 1978 (10.5 m) (Smith and Winkley, 1996).…”

Hydrologic history of the Mississippi and Lower Missouri Rivers based upon a refined specific‐gauge approach

“…They reported that the maximum change occurred in the reach between Fulton, TN, and Lake Providence, LA, where slope increased by 27% to 36% and stream power increases range from 20% to 38%. A statistical comparison of hydrologic data between early and late 20th century (Wasklewicz et al, 2004) reported a decrease in both peak and minimum monthly stages in the central part of the LMR. As previously discussed, specific-stage decreases for Q low typically can be interpreted as channel incision, while increases are interpreted as aggradation.…”

Enhanced stage and stage variability on the lower Missouri River benchmarked by Lewis and Clark

“…Stage is directly and easily measured, whereas daily discharge is calculated from stage, channel dimensions, and velocity profiles, and has uncertainties of 5%-15% (Wasklewicz et al, 2004). Moreover, stage quantifies the level of the water relative to landforms and directly affects riverine biota, especially sandbar availability, vegetation recruitment and regeneration, and habitat provision at specified depths.…”