Floods and Flooding

One of the Most Frequent of Natural Disasters

An aerial view of flooded houses in New Orleans after Hurricane Katrina.
Houses lie flooded from Hurricane Katrina September 11, 2005 in the Gentilly neighborhood of New Orleans, Louisiana. (Photo by Jerry Grayson/Helifilms Australia PTY Ltd/Getty Images)

River and coastal flooding are the most frequently occurring natural disasters and are increasing in occurrence. Floods, once purely known as "acts of God," are being rapidly enhanced by the works of humans.

What Causes Floods?

A flood occurs when an area that is normally dry gets submerged in water. If a flood happens in an empty field, then the damage from flooding may be relatively mild. If the flood happens in a city or a suburb, then flooding can cause catastrophic damage and take human lives.

Flooding can be caused by many natural things, such as excessive rainfall, extra snow melt that travels downstream, hurricanes, monsoons, and tsunamis.

There are also manmade features that can cause flooding, such as burst pipes and dam breaks.

Why Are the Number of Floods Increasing?

Humans have spent thousands of years trying to curb flooding in order to protect farmland and  homes. Dams, for instance, are built to help regulate the flow of water downstream. However, there are some man-made features that are aiding flooding.

Urbanization, for instance, has reduced the earth's capability of absorbing excess water. With extra neighborhoods comes an increase in asphalt and concrete-covered surfaces. which cover the once open fields.

The earth underneath the new asphalt and concrete can then no longer help absorb the water; instead, water running over the pavement collects quickly and easily disrupts storm drain systems.

The more pavement, the more likely a flood will occur.

Deforestation is another way that humans have helped increase the potential for flooding. When humans cut down trees, the soil is left without roots to hold down soil or to absorb water. Again, the water builds up and causes flooding.

What Areas Are Most at Risk for Flooding?

Those areas which are most at risk for floods include low-lying areas, coastal regions, and communities on rivers downstream from dams.

Flood waters are extremely dangerous; a mere six inches of swiftly moving water can knock people off their feet, while it takes just 12 inches to move a car. The safest thing to do during a flood is to evacuate and seek shelter on higher ground. It is important to know the safest route to a safe location.

A 100-Year Flood

Floods are often given designations as a "hundred year flood" or "twenty year flood," etc. The larger the "year," the larger the flood. But don't let these terms fool you, a "hundred year flood" does not mean that such a flood occurs once every 100 years; instead it means that there is a one in 100 (or 1%) chance of such a flood occurring in a given year.

Two "one-hundred year floods" could occur a year apart or even a month apart -- it all depends on how much rain is falling or how quickly the snow melts. A "twenty-year flood" has a one in 20 (or 5%) chance of occurring in a particular year. A "five-hundred-year flood" has a one in 500 chance (0.2%) of occurring in any given year.

Flood Preparedness

In the United States, homeowners insurance does not cover flood damage. If you live in a flood zone or any low-lying area, you should consider purchasing insurance through the National Flood Insurance Program.

Contact your local insurance agent for more details.

You can be prepared for flooding and other disasters by assembling a disaster supplies kit. Take this kit with you if evacuating:

  • A portable, battery-operated radio and extra batteries (know the appropriate radio station to listen to during a disaster)
  • Flashlights and extra batteries
  • First aid kit and manual
  • Emergency food and water
  • Nonelectric can opener
  • Essential and prescription medications
  • Cash and credit cards
  • Sturdy shoes
  • Extra clothes and bedding
  • Food and supplies for pets