Floods

Floods occur when more precipitation falls than can be absorbed by the ground or rivers & streams. Photo courtesy of CK-12. 

Floods are a natural part of the water cycle. A flood is an overflow of water in one place. Floods occur when precipitation falls more quickly than water can be absorbed into the ground or carried away by rivers and streams. Flood waters overflow the banks of streams or rivers and spread out over the adjacent land (called a floodplain). 

Some floods take hours or days to build, giving people plenty of time to evacuate. Flash floods are sudden and unexpected, taking place when very intense rainfall happens over a short period of time. A flash flood may do its damage miles from where the rain actually falls if the water travels far down a dry streambed. 

The destructive power of water is intimidating. When rivers overflow their banks they can carry away cars, bridges, and houses. Water is a powerful agent of erosion. People try to protect areas that might flood with dams and levees. 

Not all consequences of flooding are negative. Rivers deposit new nutrient-rich soils when they flood, so floodplains have traditionally be good for farming. Floods are responsible for moving large amounts of sediment within streams. Those sediments provide habitats for animals, and the periodic movement of sediment is crucial to the lives of several types of organisms. For example. fish and plants along the Colorado River depend on seasonal flooding to rearrange sand bars. 


Watch the following video.


Source: Flooding. Retrieved from http://www.ck12.org/earth-science/Flooding/lesson/Flooding/ on January 25, 2014. 

Last modified: Thursday, 16 February 2017, 2:23 PM