Historically, the rivers of the Pacific Northwest of the United States were a chaos of fallen timber, deep pools, and irregular currents that prevented normal flow. The logic was to clean them and remove all the trunks to facilitate the passage of water and transportation, something they did not hesitate to do. The problem is that this has subsequently been seen to be a mistake, and they have had to fix it by literally throwing logs into the river with a helicopter. Something that may seem crazy, but that science has endorsed as the best.
A bombardment of wood. The project, led by the Yakama Nation in collaboration with organizations such as The Nature Conservancy has reached an unprecedented milestone. They have managed to place more than 6,000 Douglas fir and cedar logs along the 38 kilometers of rivers and streams in central Washington.
With helicopters. A task that was not easy, and for which helicopters have been required, since access by land to these virgin areas is almost impossible without building roads that would destroy the ecosystem that they are trying to save, in a paradoxical way, ‘dirtying’ the rivers.
That is why the use of cargo helicopters has allowed the wood to be deposited with surgical precision without touching the surrounding forest floor to do as little damage as possible. An image that has actually attracted a lot of attention on social networks due to the impression of seeing a helicopter dumping wood into a river.
A dirty river. Although seeing thousands of logs piled up in a river may seem like a natural disaster, to a biologist it is a perfect work of engineering. And these stacks are called ‘Engineered Log Jams’ and they have a very clear meaning.
The first is that the logs create deep pools and shadows where the water stays cold, which is vital for the survival of salmon and bull trout in the face of rising global temperatures.
Stopping the current. This is another reason why science justifies the need to have these logs in the river, since slowing down the water allows the gravel to settle for the salmon to lay their eggs. Something that is complemented by the possibility of shelter that the trunks provide to hide from predators.
Furthermore, by forcing the water to go around the obstacles, the complexity of the channel is recovered, avoiding accelerated erosion of the banks.
The backup. As we have said before, it has not been a unilateral political decision, but rather it has had the support of science with different studies. These targeted a survival rate of 78% of fauna after major floods, more than meeting the protection objectives.
And the success has been such that they are already being replicated in other parts of the country. The public administration itself is financing similar projects on the Olympic Peninsula and in counties like Cowlitz they have redoubled their bet, placing up to 8,000 logs in the Grays River.
The return of the salmon. This project is not just a question of river aesthetics. It is a battle for food sovereignty and biodiversity. Research in the Elwha River already confirms an immediate positive response with the presence of young salmon in front of these structures.
In this way, what was eliminated decades ago because it was considered “garbage” or obstacles to progress, is today reinserted with high-tech helicopters. It is the recognition that sometimes, for nature to function properly, we need to make rivers “dirty” and full of obstacles again.
Images | Job Vermeulen Magnus Mandrup
In WorldOfSoftware | Finally we have salmon without an environmental footprint, without overfishing and without microplastics. It’s just not salmon
