Fly Fishing around the world

Biology in the river

Many fishermen ask this question: Why are the rivers cleaned?

Every time we see how the river grows people living along the river between those who are mayors, farmers and anyone else claim the “cleaning” of the river. These people also say without any doubt that the flood is serious “due to the fact that the river is not clean”.

This interpretation of the facts is erroneous and generally unanimous. In addition, many media are a permanent loudspeaker of this demand. In a recent survey in France, only those over 65 are still calling for this measure to combat flooding (“it is symbolic, traditional and political, even if it is not effective”).

What is really cleaning a river?

You always have to put “to clean” in quotes, because it is an inaccurate expression even if it is said comfortably. Actually, cleaning is to eliminate what is dirty, so in this case this verb should be restricted to remove the trash (residues of human origin) that may be in rivers. These practices are performed with heavy machinery, without environmental monitoring, without public information and without environmental impact procedure.

A useless and counterproductive action

The geomorphological and ecological damages caused by the “cleanings” of the river are enormous and in themselves justify that these practices should be radically prohibited. But in addition, they are negative actions for all citizens, since we pay them with our taxes.

In the first place the “cleanings” are useless, since in the next flood of high waters the river will again accumulate materials in the same areas, recovering to a great extent a morphology very close to the original one. If the canal is dredged, in the first few hours of the next flood the sediments will fill the gaps.

cleaning a river

The river does the cleaning

The flows are precisely the mechanisms that the river has to periodically “clean” its own canal. And the river does it well, much better than us, it has hundreds of thousands of years of experience. The river system is a system of transport and self-regulation. The canal serves to transport water, sediments and living things. With its own morphology and with the help of riparian vegetation, it is able to self-regulate its excesses and floods.

Yes, we can help the river clean by simply disposing of debris from streams by hand, without using machinery, or by removing dead wood from bridges or dams where it has been retained and can be a hazard. That the wood must be transferred to the riverside forests to remain part of the river ecosystem. These would be good cleaning and maintenance practices.

Let’s see if the reason wins and we think a little more about how a river works and what can be done to better manage the search for civilized solutions to floods. We have to look beyond the short term, because floods will continue to exist, there will always be floods, and flood zones, by definition, will flood and flood forever.

Final conclusion

The “cleaning” with heavy machinery is a destructive action of the river that does not serve to reduce the risks of flood. In addition, it can have serious consequences both in the natural environment and in the human uses of the fluvial space. Awareness and continuing education are needed to ensure that society relinquishes these actions and to promote alternative risk management and distribution mechanisms.

admin • August 28, 2017

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