LOWER MISSISSIPPI RIVER TRIBUTARIES - CONTRIBUTIONS TO THE COLLECTIVESCIENCE CONCERNING THE FATHER OF WATERS

The geological and geomorphic information preserved in the tributary v alleys of the lower Mississippi River (LMR) contributes to our underst anding of the lower valley's Quaternary geological history. Prominent Pleistocene terraces are preserved in the tributary valleys. Fisk firs t formulated his four terraces framework on the Red River. Caution nee ds to be followed in projecting the Red River terraces across the enti re Lower Mississippi Valley (LMV). The tributary system cannot be assu med to operate in a synchronized fashion in response to changes in cli mate and base level. To compare the collective contribution of the tri butaries of the LMR, the streams are described in terms of: (1) their characteristics, (2) geomorphic development, (3) process and response of the tributaries to and from the LMR, and (4) engineering investigat ions and implications. The characteristics of the tributaries are a di rect function of their drainage basin size and geology. The tributary system drains portions of six physiographic provinces. Synoptically, t he tributaries can be viewed as two groups: the eastern and western tr ibutaries. All of the eastern tributaries are intra-regional, i.e., th ey drain only one physiographic province, the Coastal Plain, and there fore, have a restricted sediment source. Generally, the eastern tribut aries are more numerous and shorter than the western tributaries. The longer western tributaries drain outside the Coastal Plain. The extra- regional nature of the western tributaries adds to the variability of discharge and sediment types. The sediment record of the tributaries r eflects response to the trunk Mississippi. During glacial outwash flus hes, many of the tributaries were alluvially drowned, producing alluvi al cones expressed as flattened longitudinal profiles. More recently, a number of tributaries in the state of Mississippi have experienced e pisodes of accelerated channel erosion. The effects of navigation and flood control modification of the Mississippi River on the tributaries have not been fully studied. Therefore, fluvial geomorphic research i n the tributaries is essential to understanding ways to mitigate the a dverse effects of river engineering, thereby designing engineering wor ks in balance with the alluvial architecture and processes of the stre am system.