Floods

What is flooding?

     Flooding is a serious concern for many people around the world.  All parts of the U.S. experience the same after effects of a flood, but what causes the flood varies depending on location.  Floods occur when a normally dry area experiences heavy rain. According to PBS, floods can be described very simply.  If we are discussing floods in our classroom, hopefully, we have previously done lessons on the water cycle.  If students understand the water cycle, then floods are simply defined as when that cycle gets backed up, the water is not evaporating into the atmosphere fast enough.  According to PBS, the following are some ways that this cycle can become unbalance:

• heavy, intense rainfall
• run-off from a deep snow cover
• over-saturated soil, when the ground can't hold anymore water.
• frozen soil
• high river, stream or reservoir levels caused by unusually large amounts of rain
• ice jams in rivers
• urbanization, or lots of buildings and parking lots

     There are also two different types of floods: the regular river flood and the flash flood.  I will go over these two different types of floods in more detail in the following paragraphs.  But first, as a future teacher I can't help but thing of this topic in the context of teaching this within a weather unit.  I would take these two different types of floods and have the students compare and contrast them.  Which do you think that we experience in Iowa? What is the difference between Iowa floods and the floods that occur along the coastlines?  These are the types of discussions that we would have based on the information they learn about different types of floods.

River Flood

     River flooding is, for the most part, fairly easy to predict.  However, it causes a lot of damage to property.  Scientists, and even residents, can tell when they are going to be flooded because they can see the river rising every day as it continues to snow or rain.  This gives authorities enough time to warn and evacuate the people living in the danger zones of the flooding area.  

     Winter weather can also cause river flooding.  Flooding in the winter time is caused by ice jams in the river.  Large chunks of ice floating in the river can get piled up.  This pile up of ice can stop the water flow in the river.  PBS explains this winter flooding by relating it to driving on an interterstate when you come upon a construction area and the multiple laned road becomes a one way.  The traffic begins to get backed up, just like the water does when ice chunks block it's flow.  

      Here are some pictures from the flooding that occurred in the Midwest United States in 2011.

Many roads were closed due to water flowing over them.

Notice how high the water is in relation to the white house in the top left-hand corner.

Many fish and other animals from the river suffered and were exposed as the water levels started to decrease.

Notice the sandbags that were air lifted to different levy breaks along the Missouri River.  In the background, baseball fans gather in Omaha for the 2011 College World Series. 

http://www.ibtimes.com/flooding-midwest-latest-photos-disaster-707337

     I would be sure to include pictures and articles from the flooding in the Midwest of the United States, because some students may be able to make personal connections to this concept of flooding.  Many people volunteered to help move sandbags in hopes to protect property. Now, let's compare what we know as flooding to what the coastal states experience. 

Flash Flooding

     Flash floods are typically the more dangerous type.  The rainfall is so intense and happens so quickly that flash floods serve a great challenge to meteorologists. However, technology is every improving and the Doppler radars have greatly assisted meteorologists to better predict flash flooding.  

     An article by Andrea Thompson discusses how lightning is able to help meteorologists predict flash floods.  She mentions that, in the past 30 years, more people have died from flooding than from hurricanes, tornadoes, or lightning (Thompson 2008).  Intense strikes of lightning may provide a warning that a flash flood is going to occur. Flash floods occur spontaneously with intense rain fall in a short period, usually several inches in one hour (Thompson 2008).  Most of the time, flash floods occur when a storm remains in one area for a long time, or when multiple storms pass through the same area repeatedly (Thompson 2008).  When this intense rain occurs, the ground cannot absorb the rain quickly enough and that is when the flooding occurs.  The flooding is usually more severe in the cities, because they have more concrete (which doesn't absorb water as efficiently as soil).  Most of the deaths associated with flash floods occur when people are in their cars and they lose control of the vehicle.  Thompson says that many people underestimate the power of water; it only takes two feet of water to float a car (2008).  

     When using lightning to predict rainfall, the meteorologists use what is call nowcasting. Nowcasting predicts weather in a shorter time scale, than compared to forecasting which predicts weather days in advance (Thompson 2008).

     Below is a video from the flood in Mississippi that happen in 1927.  This video came from the USGS website that shares water resources for the United States. 

http://archive.org/details/mississippi_flood_1927

This video, along with the information discussed about new technology that is used to predict flash floods would make a great writing assignment or discussion prompt for the students.  The students can compare and contrast past floods to present floods.  They can also compare and contrast flash floods to river floods.

Reference List

Thompson, A. (2008).  Lightning warns of flash floods.  Live Science. 
http://www.livescience.com/7611-lightning-warns-flash-   floods.htmlutm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Livesciencecom+%28LiveScience.com+Science+Headline+Feed%29 

N.A. The hows and whys of floods. PBS.  http://www.pbs.org/newshour/infocus/floods/science.html

Signal Corps of the Mississippi flood of 1927 (Producer).  (1936).  Mississippi river flood of 1927.  Internet   Archives. Retrieved from: http://archive.org/details/mississippi_flood_1927