Francisco de Asís Álvarez Romero.
Collado Villalba (Madrid, Spain) is a town located 40 km away from Madrid, next to the Sierra de Guadarrama mountain range. It has a population of 67,274 inhabitants (2025 population census) and is divided by the A-6 highway, the Madrid-Hendaya railway line, and the Guadarrama River.
These three elements had a very important role in the history of Collado Villalba. Regarding the Guadarrama River, the town’s residents used it for different activities such as bathing during the summer, washing clothes, drinking water, or extracting sand from the riverbed to build houses. Even a large factory that belonged to a company called MADE (Material Auxiliar de Electrificaciones), where most of the town’s residents worked and which was located next to the Guadarrama River, used its water to cool the products the factory produced.
However, the river’s frequent floodings caused significant damaged in the nearby streets and buildings. To solve this problem, in the 1970s it was decided to build a canal both in the Guadarrama River and in the Arroyo de la Poveda (a stream that flows into the Guadarrama River right in the centre of the village). Although this canal solved the flooding issues, the activities mentioned before were lost. Furthermore, a serious problem of pollution, filth, and foul odors arose, affecting not only the canal but also the areas where the river flowed naturally.
Recently, it was decided to dismantle part of the canal and renaturalize the Guadarrama River. The project pursued the following objectives:
- Restore the original dimensions of the river.
- Create public spaces for the use and enjoyment of citizens.
- Develop environmental education.
- Manage green areas and ecological corridors sustainably.
- Enhance the quality and diversity of riverside habitats, making the river an attractive area for biodiversity.
- Develop infrastructures that would beautify the river and the city, so as promoting tourism, commercial activities, and recreational and cultural activities.
- Improve flood defenses.
- To make Collado Villalba a benchmark with this project and turn it into a new symbol for the town.
The planned actions were expected to have positive effects on the population, wildlife, and plant species. These actions are listed below:
- Demolition of the concrete canal bottom to recover the natural riverbed, creating new habitats for animals and plant species.
- Construction of an urban river park at the confluence of the Guadarrama River and Arroyo de la Poveda, where a recreational area known as “Parque de las Bombas” is located. Part of the canal walls have been demolished to create a floodable area at river level where the new river park will be situated, equipped with features designed to withstand floods.
Picture 1: Confluence of the Guadarrama River (left) and Arroyo de la Poveda (right) in Parque de las Bombas.
(Photo taken by the author of this post on November 9, 2025).
The picture above shows two walls (the one on the left belonging to the Guadarrama River and the one on the right to the Arroyo de la Poveda), which have not been demolished yet. Between them is the earth that still needs to be removed to build the river park.
- Installation of 20 overlooks on both sides of the river, improving visual connectivity with it.
- Planting to enrich the riverbank and green areas, contributing to local biodiversity and creating an attractive space for plant species and wildlife.
- Continuous monitoring and maintenance of the riverbed with selective cleaning and clearing work to prevent blockages and improve water flow.
- Installation of river depth monitoring and measurement devices that will provide real-time data on the state of the river and send alert messages to the authorities in the event of flooding.
Picture 2: Map of the actions planned in the renaturalization project.
(Source: Collado Villalba City Council).
For the renaturalization works, it was not necessary to divert any of the affected waterways. Even so, at Parque de las Bombas, some metal panels were placed over the watercourse, and pipes were laid underneath to allow the water to continue flowing. From what I could see when I visited that area on November 9, 2025, the wildlife was not displaced. The resulting debris were stockpiled and recycled into construction material that was later used in the project (for example, for the creation of new pedestrian paths).
To inform town’s residents about the project, conferences were held and attended by city council members, local authorities, and residents, along with press conferences and promotional videos that were uploaded in the city council’s social media accounts. Even a storybook for kids (complete with a song) was written and distributed to local schools. Regarding the residents’ opinion on the project, there were, and still are, opinions both for and against the project.
The construction period was estimated in eight months, with work scheduled to begin in February 2025. The project was going to be funded by the European Union (NextGenerationEU funds, with €3,534,000). To get paid this funding, the project had to be completed by December 31, 2025. Unfortunately, the first construction company hired to undertake the project withdrew, delaying its start. Eventually, Acciona took over the project, beginning construction on October 29, 2025, and continuing throughout 2026. As the project was not finished by December 31, 2025, the city council will have to cover a great amount of the cost, which has generated controversy among residents and local political groups.
In June 2026, from what I could see, a good portion of the concrete bottom has been removed, and the river park is almost finished. However, I haven’t seen yet the overlooks installed. Furthermore, there are some parts of the canal (like the one near the bus station) that are still intact (nothing has been done yet).
In conclusion, despite the positive aspects this project would have brought, the loss of European funding due to the project’s failure to meet the deadline has had a huge negative impact. Furthermore, it appears that much work remains to be done. Only time will tell if it was all worthwhile.
To write this post, I have relied on the information published by the Collado Villalba City Council on its website.
If you’d like to find out more, here are some links that might interest you:
Link to the website for the renaturalization of the Guadarrama River:
https://www.renaturalizaciondelguadarrama.com
Link to see more photos of the project.
Link to an Instagram video from the Collado Villalba city council about the state of the urban river park at the beginning of May 2026.
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