Everyone has experienced a flood in one way or another. Whether it is water ponding on a sidewalk or a river surging through an entire city, a flood is simply defined as water existing in locations that are normally dry. The unforgiving nature of water makes floods the second deadliest weather phenomenon in the United States.
The National Weather Service in Des Moines alerts the public to two types of flooding: river floods and flash floods.
As the name implies, this type of flooding is associated with the rivers, lakes, and streams that flow across the state. While fluctuations in the height of these waterways throughout the year is quite normal, there comes a point at which rising water begins to adversely impact the surrounding towns and roadways. At this point, it is said that the river has reached flood stage. Over 100 river and stream gauges exist across central Iowa, and a flood stage has been determined for most of these sites based on analyzing the impacts of prior floods. River floods can be caused by any number of reasons, including:
River floods can vary widely in duration and intensity. Some may only briefly touch flood stage and last a few days while others can reach record heights and last for months on end, such as the Mississippi River Flood of 1993 and the Missouri River Flood of 2011.
Terms to Know:
|The Different Flood Stages|
|Action Stage||Usually a few feet below flood stage and serves as a heads up that a river is rising close to flood stage.|
|Minor Flood Stage
(or Flood Stage)
|Minimal or no property damage occurs, but possibly some public impacts.|
|Moderate Flood Stage||Some inundation of structures and roads near the river or stream. Some evacuations of people and/or transfer of property to higher elevations.|
|Major Flood Stage||Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.|
A flash flood is defined as a flood that develops in under six hours, though they can form in a matter of minutes. They tend to occur in low-lying areas with poor drainage, with urban areas particularly at risk. Some causes of flash flooding include:
Flood waters associated with flash floods tend to be fast moving, further increasing the danger for anyone attempting to navigate through them. Many people who die in flash floods are swept away as they attempt to walk or drive through the flood waters.