ABSTRACT
The US Army Corps of Engineers has observed and recorded seepage phenomena during floods along Mississippi River levees in some detail since the early 1930s, and in the early 1950s the first comprehensive studies were made of the phenomena of underseepage and sand boils. This chapter reviews and revaluates some of the findings and conclusions reached in this earlier study concerning the effect of geologic factors on underseepage; to discuss underseepage data collected along a randomly selected 40-mi reach of the river during the 1973 flood; and to relate such data to geologic mapping completed in the late 1950s. In fact, few sand boils of consequence were reported by the various teams who surveyed underseepage along the levees during the maximum height of the 1973 flood. Top stratum landward of the levees can be classified into three categories: no significant top stratum, top stratum of insufficient thickness, and top stratum of sufficient thickness.
