Flooding: Why it Happens

Flooding can happen in any part of the U.S. and each year it kills more people than tornadoes, hurricanes, wind, or even lightning!

Though flooding can be caused by many different things, there are three main types.

1. Surface Flooding
2. River Flooding
3. Coastal Flooding

Even though the causes of these different types of flooding varies, the end result is often similar.

Surface Flooding

A surface flood is considered one in which heavy rain causes flooding not associated with a body of water.

• Run-off
  Run-off occurs when rain falls on a slope and the ground is unable to absorb the water so it runs off to lower lying areas.
  This is the type of flooding caused by burn scars from wildfires or developed areas with little ground to absorb the falling rain.
• Urban Drainage
  This is the flooding that occurs in cities or suburbs from excess rainfall and poor drainage.

River Flooding

River flooding occurs when excessive rainfall and run-off causes a river to overflow its banks. River flooding can also be caused by heavy snow melt and ice jams in the spring-time.

• Overbank flooding
  Overbank flooding happens when water rises over the edges of the river or stream. This can be small streams or even some of the biggest rivers in the world.
  This type of flooding can occur far downstream from the actual rain event or snowmelt.
• Flash Flooding
  Flash flooding is the most dangerous type of river flooding. This type of flood is characterized by fast-moving torrent of water in an existing riverbed that hits with little or no notice.
  Often times flash floods are accompanied by a debris flow from what the torrent of water washes from the surface.

There are many elements that go into river flooding.  Things like, the amount of rain, saturation of soil, and geography play major roles in determining how severe a given flood might be.

Coastal Flooding

A coastal flood, as you might guess, happens in coastal areas. That coastline can be that of an ocean, gulf, sea, or any other massive body of water.
Coastal flooding is typically caused by weather such as a strong storm, tropical system, or excess runoff.

Storm Surge
A storm surge occurs when strong wind from a hurricane or storm pushes water toward shore, resulting in extreme tidal conditions.

Coastal flooding can be as small as beach erosion or as large as the devastating storm surges that destroy homes, businesses, and roads.

For WeatherNation — Meteorologist Matt Monroe