Due to the amount of water involved the tributaries were already inundated so the excess water in the Mississippi flooded 354 counties in 9 states.
The water overwhelmed levees, erased towns and destroyed other infrastructures such as bridges and airports.
Friction between moving air and the water creates drag.
Depending on the distance over which this process occurs (fetch) and the velocity of the wind, water can pile up to depths of over 7 metres.
This is due to the vast geographical distribution of river floodplains and low-lying coastal areas. It is largely classified as 'an overflowing of water onto normally dry land' .
This encompasses the simple notion that a flood involves an excess of water compared with average water levels.
This decreases the carrying capacity of the rivers, causing the peak flow of the river to increase.
Examples of the different types of floods can be found in the occurrence section.
There are many reasons why floods occur, these can be divided into categories of causes.
These are flash floods, storm surge, and dam and levee failures.
Dam and Levee Failures Dam and levees may be designed to contain a flood at a location on a water way that has a certain probability of a flood occurring in a specific year, i.e. If the flood is larger than the one predicted the structure built to contain it will be overtopped and will fail.
This causes a sudden burst of water which causes a flash flood downstream.
Failed dams and levees can cause catastrophic floods due to the intensive energy involved in the sudden burst of water.