Rivers change their course over time, but it is not because of how big they are

Rivers are alive. They change over time and the process cannot be stopped. Rivers alter the landscape of the environment they are going through, but how do they do this? Scientists from the Universities of Edinburgh and Rennes in France studied waterfalls and say that it doesn‘t really matter how much water passes in the river – coasts are formed by something else.

Waterfalls move upstream over time, but it is not because of how strong the river is – it is because of what the riverbed is made of. Image credit: Diliff via Wikimedia(CC BY-SA 3.0)

Well, of course it is water that is washing away the shores. However, over time rivers change direction and that is not because of how much water passes. This happens because of the rock that shores are made of. The material which forms the river bed is pretty much the key to where the river is going to flow in the future. For example, waterfalls tend to migrate upstream over time. This changes the entire landscape, which can be a problem for land owners.  At first scientists conducted experiments in a laboratory.

Laboratory experiments involved a scale model of a river with a waterfall. Scientists determined that the upstream move is influenced mostly by the composition of the river bed, rather than by the water flow. For example, waterfall remained in the same position when the river flow was altered. In fact, rivers proved to be adaptable to the changes in water flow. However, changing riverbed material in the site of the waterfall greatly influences its move upstream. These findings go hand in hand with results of previous researches that revealed how changes to the landscape are not determined by changes in the water flow. It doesn’t really matter how big the river is – relatively small waterfalls in Scotland may migrate faster than the Niagara Falls.

While it is nice to know that rivers change over time, it may cause problems. Rivers erode the landscape, which is important for landowners and preservation efforts. It can also have an effect on, for example, where new building will be constructed. Dr Mikaël Attal, one of the scientists from the study, said: “Accurately modelling how rivers change is important for understanding landscape evolution in the past, present and future. The nature of the rock on the river bed plays a more important role than the size of flow in influencing how rivers evolve, and ongoing studies should take this into account”.

It is not difficult to see where the river used to be. However, people change the landscape quite a lot. This may have implications even on historical researches, because if a source mentions a river, you cannot be sure about the specific location.


Source: University of Edinburgh

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