Flood for thought: Fluvial flooding

Back with another installment of flood for thought, today we’re going to be covering fluvial flooding, also known as river flooding. Fluvial flooding is one of the two main categories of flooding – fluvial or pluvial. (we’ll be covering pluvial next week)

Looks can be deceptive. A calm, gently flowing river might not seem like it could ever cause destruction or death, but it can. Fluvial flooding occurs nowhere near as fast as flash flooding (its in the name), although it can be just as dangerous. Fluvial floods occur when rivers burst their banks as a result of heavy rainfall. Rain falls directly into the river but also saturates the earth so much that it also runs off the surface and into rivers. Fluvial flooding usually happens on a huge scale because of the length of some rivers. Smaller rivers also feed into larger rivers meaning that entire and towns and counties can be affected by fluvial floods – Villages surrounded by rivers can be cut off from the outside world by both transport access and communication. Even areas further downstream that might not have even seen much rainfall can be heavily affected.

The severity of a river flood is simply determined by the amount of rainfall across the area of the river(s), more rain means more destruction. River flooding can be seen coming much longer before it actually happens, unlike flash flooding. This means that precautions can be put in place and if needs be, people can be evacuated from their homes before flooding actually occurs. 

Those who face the most danger from a fluvial flood are those living closest to a river/dike/bank that has been breached. This is because at the time of breach the speed at which the water flows is immense and can be compared to that of a flash flood. Cars and large objects will be moved due to the sheer strength of the water, however, as the water moves further away from the breach onto lower ground the water begins to ‘stand’ rather than flow.

One of the worst river floods to date is the flooding of Hull via the river Hull in 2007 – 96mm of rain was recorded prior to the flood. One life was lost, 9000 homes and businesses were flooded as well as 95 out of 98 schools. 6300 people were forced into temporary acommodation, some for over 12 months. It goes to show that fluvial flooding, although not as immediate as flash flooding, is still dangerous.

If you have any questions or photos of flooding that you would like to share then please get in touch! Email me at Kevin@floodsense.co.uk