What is a Megaflood?

In this video, Dr Dan Hobley explains the difference between floods and megafloods.

Megafloods are caused by something entirely different than regular floods. Regular floods are caused by rainfall whereas megafloods are:

Megafloods

caused by a large volume of water being released from behind some kind of store

Types of stores

In the video, a number of different stores that can cause megafloods were mentioned.

Artificial dams

Two extreme events in our recent history we referenced were both caused by the failure of artificial dams.

1975 Banqiao dam failure, China

The failure of the dam led to 701 million cubic meters of water being released in 6 hours.

2015, Bento Rodriguez dam disaster, Brazil

Around 60 million cubic meters of iron waste was released into the Doce river and eventually into the Atlantic ocean.

Natural dams

Megafloods can also be caused by the failure of natural dams.

These are formed when a landslide or glacier blocks a river. If these are particularly large they can store vast amounts of water.

One recent example of a landslide blocking a river is in Attabad, Pakistan. In 2010 a massive landslide blocked the Hunza river and created Attabad Lake.

Changes in sea level

Another cause of megafloods are changes in sea level. This type of megaflood occured around 450,000 years ago in the Dover Straits, between modern day England and France.

Map of the Dover Straits between England and France by NormanEinstein is licenced under CC BY-SA 3.0

In this case the Dover Straits which were previously a dry river valley were completely flooded due to gradual changes in sea level. This separated modern-day England and France.

This was a truly extreme event that left a lasting impact on our planet.