ABSTRACT
This chapter focuses on the general physical and morphometric changes associated with the 1993 flood, including soil erosion, channel scours, bank erosion, and the movement and deposition of eroded sediments and chemicals. Most of the streambank erosion occurred in high-energy areas where old meander loops existed, and bank erosion occurred on the outside banks of the rivers. During the 1993 flood, the Missouri River's velocity remained quite high, even with numerous levee breaches, due to the existence of narrow floodplains. Levee breaches were associated with scour hole development followed by deposition of sediment in a fan-shaped area extending in the downstream/down valley direction. The chapter discusses effects on river water quality extending down the lower reaches of the Mississippi River and into the Gulf of Mexico. During the latter part of the flood, ground-water levels essentially mimicked river water levels, and high groundwater levels can be responsible for extensive flooding in lowlands adjacent to the rivers.
