Types of floods

In this lesson, we shall look at three major flood types: Flash floods, Rapid on-set floods, and Slow on-set floods.

Flash floods
This kind occurs within a short time (2-6 hours, and sometimes within minutes) and is usually a result of heavy rain, dam break, or snowmelt. Sometimes, intense rainfall from slow-moving thunderstorms can cause it. Flash floods are the most destructive and can be fatal, as people are usually taken by surprise. There is no warning, no preparation, and the impact can be very swift and devastating.

Flash flood fact from Colorado USA, 2013
Flash flood fact from Colorado USA, 2013

Rapid on-set floods
Similar to flash floods, this type takes slightly longer to develop and the flood can last for a day or two only. It is also very destructive but does not usually surprise people like Flash floods. With rapid on-set floods, people can quickly put a few things right and escape before it gets worse.

Slow on-set floods
This kind is usually a result of water bodies flooding their banks. They tend to develop slowly and can last for days and weeks. They usually spread over many kilometers and occur more in flood plains (fields prone to floods in low-lying areas). The effect of this kind of flood on people is more likely to be due to disease, malnutrition or