A flood is an enormous amount of water. If the street is full of water, it's flooded. Too much of anything can also be called a flood.
Whenever it rains and rains and rains, there's the danger of a flood, a type of disaster where water is out of control. Because a flood is so powerful, people use the word when overwhelmed by other things. A top college graduate could be flooded with job offers — that's a good kind of flood. People can also be flooded with emotion. Words with similar meanings are deluge and overflow. Too much — or just a lot — of anything can seem like a flood.