How Does Rain Cause Floods?

Question

How Does Rain Cause Floods?

3 Answers

Answer Question

Answer 1

A flood can occur due to several reasons including heavy and intense rainfall. A number of other factors that can cause a flood include run-off from a deed snow cover, when the ground can't hold more water or over saturated soil, ice jams in rivers, urbanization or a lot of buildings and parking lot.

There are two types of floods, a regular river flood and a flash flood. A flash flood is much more dangerous and approximately 92 people die in flash floods every year. Flash flood is not caused particularly by rain but is always accompanied with heavy and intense rainfall.

Rain can cause a river flood and a flood in a city. As it rains heavily and continuously, the water level in a river starts to rise and goes over the edges of the river, which leads to a flood. In urbanized towns, a flood can occur due to heavy rainfall as most of the land has been covered with concrete. There is a very little soil land left to soak the water, which leads to saturated soil and causes a flood.

Answer 2

The flood plain, of a river is normally grassy and normally steep ..
As the rain fall hits the surface of the flood plain, if the ground is impermeable the water will not seep through and will become 'surface run off' and due to the gradient of the hill gravity will pull down the rain fall at a faster speed, as their is more rain fall and it is not be soaked up by any vegetation (when it is it is called vegetation interception) and it is moving down towards the river at a faster rate .. The water hits the river and begins to make the water levels rise, each river has what is known as 'bank full' which is the max amount of water a river can carry before flooding ... The excessive amount of water means the river fills up more quickly and therefore floods more.

Answer 3

"Normal" stream and river levels are what result from the "normal" water runoff from an area. (The area associated with a particular stream is called its watershed.) When the amount of water that is to be drained from an area increases, as from "excessive" rainfall, the stream and river levels must rise to accommodate the extra volume. When they rise enough, we call it a flood.

When one considers that variation in rainfall is the usual condition, what constitutes "normal" and what constitutes "excessive" is largely a matter of experience. For example, I have only experienced once in my lifetime the condition that the Missouri River in central Missouri filled its valley from bluff to bluff (many miles across the flood plain). However, the existence of such a flood plain is evidence that it happens regularly in geologic time.

Engineers and insurance underwriters base their decisions about what economic activity to allow on the history we have accumulated as a society. In many cases, it is clear that our recent historical experience is different from long term variations that are possible.