Floods are arguably one of the worst natural disasters we face on our Earth today. They can strike within hours, sometimes destroying entire neighborhoods, leaving thousands without homes. They affect nearly everywhere on the globe, and are extremely hard to rebound from. Some floods take days to develop; others strike in a few hours. No matter the type of flood that may hit an area, it is important that we understand what exactly floods are, and why they happen, so that we can make their impact minimal, not only for us, but for the environment as well. So, in this post, I will be discussing what floods are, why they happen, and how humanity might have made them such a large problem.
What Exactly is a Flood?
We all know the general definition of a flood: a natural disaster that causes normally dry ground to overflow with water. However, there are actually many different classifications of floods that are not talked about. Understanding these types of floods can help us better prepare for them when they may hit our area of residence. Here are the three major types of floods:
(Big thanks to intermap.com for providing the information used in this section).
River Flood (Fluvial)- Fluvial floods are caused when a large amount of rainfall causes a river or stream to overflow. This is the most well known type of flood, and is the most common as well. While the main cause for this flood is excess rainfall, they can also be caused by heavy snow melt and ice jams (when lots of water builds up behind a heavy block of ice). Within the classification of a Fluvial flood, there are two more sub-types that help to specifically define the type of flood. They are:
Overbank flooding- when the water in a stream of river overflows from its edges.
Flash flooding- when a very high torrent of water is generated in a stream, causing it to overflow with very little notice (more dangerous).
Surface Flood (Pluvial)- this type of flood occurs when heavy rainfall itself creates a flood, rather than heavy rainfall near a river. Because they occur independent of a body of water, these types of floods can happen anywhere; you don't have to live near a river or stream to be affected. While it is more common for these types of floods to happen in areas with a lower elevation, they still can happen in higher elevated areas. Like Fluvial flooding, there are two sub categories withing Pluvial flooding that help to further define the extent of the flood. These are:
Urban drainage system overflow- the heavy rainfall fills a town's drainage system causing excess water to flow into the streets.
Run off- floods cause by water that flow down from nearby hills that are unable to absorb the water. They occur most often in areas that have had recent forest fires.
Coastal Flood (Surge Flood)- the final type of flood, known as a Surge Flood, only happens in areas that are near to a large body of water, such as an ocean or lake. They are normally caused by extreme tides, which in turn can be caused by severe weather in that particular ocean/lake. These tides push excess water onto the land nearby. If there are neighborhoods near these bodies of water, they can be very easily overrun and destroyed by a Surge Flood. More often then not, this flood affects lower elevation ground. There are three different categorizations for Surge Floods. They are:
Minor: the flood only causes a little bit of beach erosion, and causes very little or no damage to nearby buildings.
Moderate: a fairly large amount of beach erosion occurs, and there is damage to nearby buildings.
Major: the flood causes extreme beach erosion, and lots of damage not only to buildings in that area, but to infrastructure such as roads as well. When these floods occur, residents in that area should be evacuated.
What causes floods?
So, now that we know what the different types of floods are, why are they caused? Very similar to a drought, the cause of a flood seems obvious: too much rain! While this is true, different areas of the world have characteristics that leave them more susceptible to floods than others. Here are some common characteristics of areas that are more likely to have a flood than others:
The resting water level of a river is high- often times, if a river near an area has a normal, resting water level that is very close to the top of the ground nearest to it, it is susceptible to flooding. It is hard to identify what exactly "close" is, as it is different in each area. However, a good rule of thumb is that if a river's water level is at least one foot away from the top of its bank, then it will be safe during most floods.
Low vegetation- areas that do not have much vegetation (trees, grass, bushes, etc.) are more susceptible to flooding. This is because the ground in that area cannot absorb water very well, causing easy overflow.
Topography- if you live in a lower elevation area, then floods are more likely to occur. If you live at the bottom of a hill for example, rainwater from the hill will build up in your area, and it would have no place to go because you are at the lowest point in the area.
Are We Responsible For These Floods?
Over the past few decades, the severity of many floods throughout the world has begun to increase. This has been seen all throughout the world, from the Louisiana area, even to the Northeast in the past few days. Many debate whether or not these "super-floods" are a product of human pollution and Climate Change. Like droughts, floods occur naturally, and we will likely never be able to stop them, however there is a pretty straightforward correlation between Climate Change and floods, and it has to do with the water cycle. As the Earth continues to warm, more and more water is evaporated from the ground. This disrupts the balance in the water cycle. Instead of having a constant period where some water in condensation and some of it remains in the ground, we see more drastic periods where either all of the water is in collections, or all of it is in condensation.
A drought is caused when most of this water is being evaporated, leaving little to none for the wildlife below. Then, when rainfall finally occurs, it is so much stronger than normal, because of all the water that had been built up previously. This causes floods to occur more frequently, and with a much stronger force.
Conclusion
Of course, I can't hope to cover all the information you need to know about floods in one post, without it being thousands of words long. So, in next week's post I will be covering how you can protect yourself from floods, and do your part to limit the amount they occur. Until then, if you would like to learn more about floods, please feel free to visit the links I have provided down below. They give some great information that I was not able to cover. Thanks for reading.
All credit for information used in this article goes to:
http://www.nationalgeographic.com/environment/natural-disasters/floods/
http://www.intermap.com/risks-of-hazard-blog/three-common-types-of-flood-explained
http://www.ga.gov.au/scientific-topics/hazards/flood/basics/causes
http://www.weather.gov/aprfc/terminology
Images:
http://www.couriermail.com.au/news/special-features/in-depth/how-the-floods-changed-brisbane/newsstory/14a422da6bf5ff6ed5d52f3df2de8087
https://www.yahoo.com/news/thousands-evacuated-floods-batter-paris-191008609.html
http://www.dailymail.co.uk/news/article-2238931/UK-floods-The-city-sank-storm-Woman-dies-5ft-wall-water-drives-hundreds-homes.html
https://oshmatters.wordpress.com/2015/10/19/the-flooding-is-imminent/
http://www.timesunion.com/news/article/New-England-braces-for-coastal-flooding-4338092.php
http://www.atta.travel/heritage/2016/06/default.aspx
http://reynolds.asu.edu/topo_gallery/intro_title.htm
http://www.cnn.com/2016/06/25/us/west-virginia-flooding-deaths/
http://www.printablediagram.com/diagram-of-water-cycle/
https://pdrmacomb.wordpress.com/
Comments