Floods Are Written in the Rivers

PROBLEM: Predicting extreme river flooding has typically been based on whether that river has already flooded in the past. However, “[f]or this method to work, you have to wait for something bad to happen,” notes Stefano Basso of the Norwegian Institute for Water Research.

SOLUTION: Basso and colleagues developed a technique to identify the susceptibility of a river to extreme flooding regardless of whether it has a history of floods. They studied 30+ years of discharge and flooding data from more than 100 rivers in Germany and the United States, separating the flood data into two categories: small floods that would be expected for that particular river, and extreme floods that were 20–35 times larger than a normal flood for that river. They studied the properties of the rivers with extreme floods, including frequency and quantity of rainfall and the amount of time it took water to flow from surrounding regions to the river. The researchers determined that the structure of stream networks and types of river flow define a river’s extreme flood risk, and they identified two specific critical variables: the river basin’s capability to retain and release water, and the proportion of rainfall the river receives versus the amount of water that evaporates from the area. The research team then used these parameters to assess the vulnerability of more than 2,500 U.S. and German rivers to extreme flooding. They identified a number of rivers that have never experienced a severe flood but are at risk based on the two parameters, including the Baron Fork of the Illinois river and the Cowpasture River in Virginia, and they have expanded their research to include other locations. Their research was published in Nature Geoscience. [Source: New Scientist]

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