How does it form?
Anywhere where rain falls a flood can form. Floods usually occur when there is so much water that it won't drain into the ground or run off. It can also happen when a body of water overflows, ice/snow is melting too fast, or a dam breaks. It can take days to form. Places with lots of flooding are called flood plains. Flash floods happen extremely quickly after heavy rain because the water can't soak in causing puddles. The puddles overflow and creates floods. Regular floods can take a while to form while flash floods can form in minutes. This makes flash floods more deadly because we aren't as ready for them as we are regular floods.
Where has it happened?
In 1927, the Mississippi River flooded a great amount causing 500 people to die and 600,000 people to be homeless (http://content.time.com/time/specials/packages/art.... 16 million acres of land were destroyed. Later in 2011, the Mississippi flooded again. This time it wasn't as severe. It was caused by lots of snow melting and made the Mississippi overflow. The area lost $3-$4 billion. This flooded 200 square miles. 3,500 people escaped.
Comparing and Contrasting: Both of these flooded places \and caused damage to the land. They both made the area lose a money and made them have to pay for damages. In 1927, many people died where as in 2014, few if any died. Probably few people died because they get a warning because of technology. They also have better supplies for their house which would help keep the flood at bay.
Impact on Mankind
Not many people died in 2014 and there wasn't as much damage because now people know how to prepare and use those ideas. People who live by places that flood often may not have basements so that the basement doesn’t flood. If they hear a flood is coming, one place you wouldn't find them would be the basement. They also build gutters to instantly get the water away from anything important. Around some parts of the river, humans have built walls to ward off the water from the Mississippi River. Because of floods, thousands of people have died over the years and many properties have been damaged. People had to adapt to save themselves from this kind of severe weather.
In Key West, after Hurricane Wilma, in October 2005
2007 Jakarta flood, in Jakarta, West Java, Banten
"Flood Information, Flooding Facts, Flash Floods, Photos -- National Geographic." National Geographic. Web. 12 Mar. 2015. <http://environment.nationalgeographic.com/environment/natural-disasters/floods-profile/>.
"Mississippi River Flooding to Impact Communities, Port Operations." AccuWeather. Web. 17 Mar. 2015. <http://www.accuweather.com/en/weather-news/mississippi-river-flooding-barges-communities/29380510>.
"Extreme Weather 2011." NOAA:. Web. 17 Mar. 2015. <http://www.noaa.gov/extreme2011/mississippi_flood.html>.