Why flooding can kills plants?

How can I effectively design my lawn slope for drainage purposes? How is rohypnol grown? How can I successfully grow a mimosa tree? Does green grass have sugar in it? Are rye grass and fescue grass in same family of grasses? How much light does a dieffenbachia require to thrive? How can I effectively prevent and manage leaf mold on my tomato plants? What is the small yellow edible plum like fruit of an Asian evergreen tree called? Why does the bearberry only bloom in between march and June? How can I effectively deter geese from my property? What are the examples of fertilizers? What does a star on your palm mean? How can I effectively prevent and manage the growth of yellow fungus in my houseplant soil? Are there any sassafras trees in PA? Are any parts of a carnation poisonous to humans? If you cut sunflowers back will they grow again? Will hydroxyzine stop poison ivy itching? Why aren't my seeds sprouting despite following all the necessary steps for germination? Were plants or humans on earth first? Why do you grow plants in a greenhouse and not outside?