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Floods

Floods. NOVA Video. https://www.youtube.com/watch?v=WvJlENenpJA How are floods different than other types of natural disasters? How did the flood begin? Be detailed. Why does a river need to periodically occupy its floodplain? What is the best way to prevent a city from flooding?.

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Floods

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  1. Floods

  2. NOVA Video • https://www.youtube.com/watch?v=WvJlENenpJA • How are floods different than other types of natural disasters? • How did the flood begin? Be detailed. • Why does a river need to periodically occupy its floodplain? • What is the best way to prevent a city from flooding?

  3. Bellringer • What causes lightning?

  4. Objectives • Complete lightning quiz • Finish answering all the questions about the flood video

  5. 23 min • Why is it sometimes a good idea to break open a levy? • How long did Valmeyer stay underwater? • Where did Valmeyer move to? Why? • How can you flood proof your house? • What are humans doing that make floods worse? • Why is the government buying back flood plains?

  6. Bellringer

  7. Objectives

  8. Lightning Quiz • Class average was a 77.

  9. Floods • Where does all the water come from? • Watershed: An area of land where surface water from rain and melting snow or ice converges to a single point at a lower elevation.

  10. Flooding • What factors do you think effect the intensity of a flood? • What factors do you think effect the duration of a flood?

  11. Flood Intensity • The intensity of a flood is determined by the amount of rainfall and the amount of time that it rains. • The worst floods happen when there is heavy rainfall over a long period of time. • Flash flooding happens when there is very heavy rainfall for a short period of time.

  12. Duration of a Flood • The duration of a flood is determined by the amount of rainfall, the amount of time it rains, and the areas ability to get rid of the water. • Flashfloods show up quickly, but also move on quickly. • Heavy rainfall for weeks, or months produce the worst duration of flooding.

  13. Duration of a Flood • If the ground soil can absorb the water from the flood quickly, it will decrease the time the area is flooded. • Some areas have rivers or lower level land which can help divert or move out the excess flood water.

  14. Changing the Landscape • How do you think deforestation (cutting down natural landscapes), and urbanization (building cities) has impacted flooding?

  15. Deforestation • Deforestation causes faster runoff of water from the watershed and into the river. • Leaves on the ground allow water on them to evaporate instead of flowing away. • Leaves reduce raindrop impact, and gentler rain causes less erosion. • Tree roots absorb water from the soil. • Tree roots hold soil in place, and reduce erosion.

  16. Urbanization • Pavement is even less absorbent than naked soil, so it causes even quicker runoff. • Sewer systems also help expedite the water from a city. • These variables also cause flash floods in rivers and towns downstream from the city to become more frequent, and more severe.

  17. Flash Flood vs. General Flood • Both flash floods and floods can be extremely dangerous. • Flash floods generally happen quickly after very heavy rainfall, and they can be hard to forecast and predict. • Flash flood waters move at very fast speeds, and can roll boulders, tear out trees, destroy buildings, and obliterate bridges.

  18. Flash Floods • https://www.youtube.com/watch?v=NXPNWFBd3h8 • Flash flood water walls can reach 10 to 20 feet. • Results in localized flooding typically occurs in hilly or mountainous terrain, but also occurs in urban areas. • Fatalities are more common than with general floods. • The best response to a flash flood is to move immediately and quickly to higher ground.

  19. General Floods • General floods involve the whole watershed, and take at least several days to build up. • General floods can even build over months. • Water level rises slowly, but consistently. • The best response is to seek higher ground, but usually these floods won’t sneak up on you.

  20. General Floods • Stream gauges monitor water levels so they are fairly predictable

  21. General Floods • Can results in wide-spread flooding. Flood-plain areas are prone to flooding. • A flood is said to be occurring when a stream or river rises above its channel. The level of flooding is reported as “feet above flood stage”. • Fatalities are few in the US from general flooding; however, the economic cost is high

  22. The 2011 Flood • http://www.erh.noaa.gov/bgm/WeatherEvents/Flood/september072011/ • How did it compare to the video we just watched?

  23. Dangers of Floods • The force of six inches of swiftly moving water can knock people off their feet. • The best protection during a flood is to leave the area and go to shelter on higher ground. • Cars can easily be swept away in just 2 ft of moving water. • If flood waters rise around a car, it should be abandoned.

  24. Dangers of Floods • Floods are the most common and widespread of all natural disasters – except fire. • Most communities in the US can experience some kind of flooding. • Like many other natural disasters people are often injured because of their neglect for the severity of the event.

  25. Dam Failures • Dam failures are potentially the worst flood events. • A dam failure is usually the result of neglect, poor design, or structural damage cause by a major event such as an earthquake. • When a dam fails, a gigantic quantity of water is suddenly let loose downstream, destroying anything in its path.

  26. Killed by Floods • The count of flood deaths is highest in South America, Southern Asia and Eastern Asia. • Central Africa, Japan and Western Europe each account for less than 0.6% of flood deaths. • Approximately 10,000 people in the US have died from flooding since 1900.

  27. Killed by Floods

  28. Worst Flood Ever • An estimated 3.7 million people died in central China in 1931 from one ongoing flood. • Heavy snowfall in the winter started to thaw in the spring. • The spring had very heavy continual rain that only grew heavier as spring became summer (more than 2ft of rain per month). • The flood was at its peak from July to late August.

  29. Worst US Flood Ever • 51st worst flood in the world. • 2,209 people died. • Occurred in Johnstown Pennsylvania in 1889. • It was triggered by a failing dam, not months of continual heavy rainfall. • First major disaster relief effort handled by the American Red Cross.

  30. Checkpoint • Which is worse, a flash flood or a general flood? Why? • Which areas of the world suffer the most deaths from floods?

  31. Engineering Around a Flood • http://ees.as.uky.edu/sites/default/files/elearning/module12swf.swf • Test out how a flood will effect the three different types of regions. • Then change the type of flood control to use in the area. • You will record your results.

  32. Flood Data

  33. Flood Questions • What do you think is the best way to prepare a city for a flood? Why? • What do you think is the best way to prepare a farm for a flood? Why? • What effect will construction cost have on which design you would pick?

  34. http://www.discoveryeducation.com/teachers/free-lesson-plans/flood.cfmhttp://www.discoveryeducation.com/teachers/free-lesson-plans/flood.cfm

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