Flash Flood! is built using real scientific data collected in the field. The field site is the Thinhope Burn river in the north of England, part of the South Tyne river system. on July 17th 2007, a small but very intense convective storm centered over the upper reaches of the river catchment, and 59 mm of rain fell in a few hours. This triggered landslides in this part of the river which clogged the channel with debris, causing the building flood water to pool and travel down the river in what was described by witnesses as a “wall of water”.
The water level rose rapidly and the was powerful enough to move rocks and strip away the plants by the river channel. Some even said they could hear the sound of boulders bouncing along the river bed. After the flood, the river valley was scarred, and the once stable and narrow channel became braided and dynamic.
Screenshots of Google Earth showing a section of Thinhope Burn in 2003 and another a short time after the 2007 flash flood from intense rainfall (FFIR) event – the white boxes show the approximate extent of the Flash Flood! environment (thanks to Dr David Milan for these).
Dr David Milan, a Geomorphologist from the University of Hull, has been studying the Thinhope Burn catchment for many years. A Geomorphologist, like David, studies how the landscapes change over time by natural processes, such as wind or water, and he was interested in Thinhope Burn as the valley has a series of terraces which indicate a former location of the river in the past. He can calculate how long it has been since the river last flowed over the terraces and this helps us understand how our landscapes and climates have changed over time.
As part of his research, in 2004, David used a highly accurate Global Positioning System (GPS) strapped to his back to measure the height of the land as he walked up and down the river valley. After the flood, David was able to do this again and calculate how much the river has changed, and by repeating this every few months he can begin to build a picture of hoe the river valley adjusts and recovers after an event like this. More recently, David plus Chris Skinner and Matthew Perks from the NERC-FFIR programme have started using a more accurate and detailed Terrestrial Laser Scanner (TLS) to record this information.
Understanding how rivers recover their stable forms after flash flooding from intense rainfall (FFIR) events, and how long this takes, is important to understanding the change in flood risk with our changing climate. In the UK it is expected that the number of intense storms will increase, and with it flash floods, and these carry a lot of sediment and can cause rivers to travel by a different path altogether – it is likely that our rivers will become more dynamic as a consequence and this will impact on future flood risk. Understanding this is a key aspect of the NERC-FFIR programme.
You can read more on Dr David Milan’s research on Thinhope Burn in this paper (paywall).