Floods cause disasters, but they can also be beneficial. Whenever a river overflows its banks,
it dumps sand, silt and debris that it has carried downstream onto the surrounding land. After
the flood waters move away, the soil is more fertile, because of the organic matter and minerals
in this material. That is, as long as there's not too much sand!
Farmers since the time of the ancient Egyptians have known about the benefits that a flood
can bring. Indeed, the ancient Egyptians planned their farming, and their lives, around the
regular flooding of the Nile. They learned over time that, the higher the flood, the better
that year's harvest would be.