http://ericir.syr.edu/Projects/Newton/12/Lessons/floods.html#main activity
It is hard to believe that a small, slow-running stream could cause harm. During a flood, however, even the calmest brook can become a torrent and cause unforeseen misery and damage. http://nrcdec.nrc.state.ne.us/floodplain/mitigation/mitigation.html
• 90% of all Presidentially-declared disasters since 1990 have been due to floods.
• 64% of all flood-related fatalities in 1998 occurred after vehicles tried to cross flooded roadways.
• Floods cause 40% of all fatalities from natural hazards.
• In the 1990's annual flood damage has risen over $4 billion.
• The worst flood in American history happened in 1900 when a hurricane submerged Galveston Island, Texas, killing at least 6,000.
• Some of the worst floods in American history have happened because of dam failures. Examples:
Johnstown, PA in 1889 killed 2,209Rapid City, SD in 1976 killed 243 people and caused $165 million in damage.
• The force of 6 inches of water can wash people off their feet; less than 2 feet of water can float cars.
• Accumulated debris of ice, often at bridge piers and channel constrictions, can lead to worse flooding. Water can rise in minutes rather than hours.
When these dams let loose, they can send walls of water downstream, causing further flood problems.
• Once the flood water recedes, cleanup and aftereffects can claim more lives through disease and accidents.
Many people like to live near a body of running fresh water. Rivers and streams provide recreation, food and, drinking water. But when rain or melting snow produces large amounts of water, rivers and streams may flood, causing problems for those who live nearby. Although we describe floods as disasters, they are, in fact, natural phenomena.
To minimize the effects of a flood, engineers, build levees and dams to constrict the overflow of rivers. As more communities build levees, the water in a river is forced to run at a higher level because it cannot spread out. Water behind a dam builds up and forms a reservoir that is later used to supply the area with water for drinking, irrigation, and recreation. The deeper the water, the greater the pressure. An activity to demonstrate why forcing water to stay within a small area puts it under pressure can be found at: http://ericir.syr.edu/Projects/Newton/12/Lessons/floods.html#insights
Investigations for your students:
1. Is there a problem with flooding in your area?
2. What plan could you develop to improve the situation? Who would need to be involved?
3. Has there ever been a major flood in your area?
4. What measures have been taken to help prevent it from reoccurring?