Do You Know Why does it Floods?

If it rains hard and long enough, low lying areas are at risk of flooding. It is a natural occurrence caused by heavy rain.  Flooding is caused by too much rain in too little time.  Human activity influences the frequency and severity of floods, but they are created by Mother Nature.

According to Frank Richards, a National Weather Service hydrologist (a water scientist), "There's more water flowing through the hydrological system than the system can draw off, A flood is an imbalance."

There are two basic  types of floods, Regular River Flood- water slowly climbs over the edges of the river. Flash Flood- when a wall of water quickly sweeps over an area.

Extra water has to go somewhere. Our creeks have a limit of how much water it can hold. When too much rain fall in  just a little time, creeks naturally overflow onto the floodplain. Floodplains are the areas along streams or rivers that are likely to experience repeated flooding. Over thousands of years, nature shaped the floodplain to hold excess water that spills over the banks. Floodplains are designed by nature to flood.

Homes and buildings were often built in floodplains because water was easily available for drinking or commercial uses, floodplain land is often flat and easier to develop than hilly land. It is important to regulate development in higher-risk areas.

Credit: Flood Factors Diagram

A number of factors can contribute to flooding:

• Heavy, intense rainfall

• over-saturated soil, when the ground can't hold any more water.

• High river, stream or reservoir levels caused by the unusually large amounts of rain

• Urbanization, or lots of buildings and parking lots

• Ice jams in rivers

• Frozen soil

• Run-off from a deep snow cover

References:

The Hows and Whys of Floods

Why does it Flood?