Why Might a Several-Week Rise in the Mississippi or Missouri

Why might a several-week rise in the Mississippi or Missouri River cause earthen levees (built of soil and sediment) along the riverbanks to fail?

A) The water tables in the levees would rise with the rising river levels
B) Floodwaters would drown plants on the levee banks, kill the plants and roots, and thereby decrease the soil-binding effects of the plant roots on the levees.
C) Rains would wash away the levees.
D) All of the above are correct.