It is not new to science that earthquakes are capable of altering the course of rivers. In 2016, a 7.8 magnitude earthquake in New Zealand knocked the Waiau Toa River — also known as the Clarence River — out of its original path, causing flooding in the surrounding area and never returning to its former path. Now, a study by researchers in the country is trying to predict which areas may be affected by water in similar events.
While floods and earthquakes are already among the most damaging disasters around the world, little has been studied about the simultaneous occurrence of these phenomena. It may seem rare, but tens of thousands of active geological faults in the earth’s crust meet the course of a river – and where this encounter happens, the risks overlap.
During an earthquake, the blocks of rock on either side of a fault can move vertically relative to each other, creating gaps from a few centimeters to several meters. In 2016, the Kaikōura earthquake caused a blockage in the Waiau Toa channel, with a permanent rise of 6.5 meters in height, changing the path of the river.
How to predict these phenomena?
There is no way to predict exactly where and when earthquakes will happen, but knowing the geological faults in a region and where they pass through water courses, researchers are already able to estimate areas that may be affected by changes in the course of rivers caused by tremors.
For this, the New Zealand team built two computational flood models, trying to simulate the behavior on the fault that broke in 2016 — the results could be validated through the real world, seeing where the river started to go. Although it is not possible to know how much vertical displacement will occur, the tool allows investigating the extent of impacts in scenarios where it is greater or lesser. Furthermore, the models showed that if the river volume is low at the time of the tremor, the course change will be significantly slower.
The results show how being prepared can save lives in disasters like these. The two discoveries allow authorities responsible for risky locations to plan emergency actions or even preventive measures in relation to these floods, such as the construction of dams.
Source: Science Advances via: The Conversation
