Valencia Floods: What Really Happened?

18 December 2024

Miguel Cano of Anglian Water talks to Planet Possible host Niki Roach about the devastating flooding that hit the Spanish city in October 2024

This month on CIWEM’s Planet Possible podcast, host Niki Roach talks to Miguel Cano, a principal hydraulic modeller at Anglian Water who was raised in Valencia, about the devastating flooding that hit the Spanish coastal city this past autumn.

Here we bring you a taster of that illuminating conversation, with Niki and Miguel discussing the challenges inherent in Valencia’s unique flood risk infrastructure.

If you like what you read, you can listen to the conversation in full here or search for Planet Possible in your favourite podcast app or on Spotify. Subscribe so as not to miss any of our in-depth monthly episodes.

Planet Possible tells the stories of the people paving the way for positive planetary and societal change, so join Niki as she explores what's possible with practitioners and visionaries working on the big issues, from resilience to climate change, to enhancing our natural environment, to improving equality, diversity and inclusion in the environment sector. You’ll find the Planet Possible MiniPod on the same feed, bringing you a monthly 15-minute burst of topical environmental discussion with some of the leading voices in water and environmental management.

Now, over to Niki and Miguel…

Niki Roach: Bienvenudos a Planet Possible, Miguel. You are in Valencia at the moment. Tell us what it's like there.

Miguel Cano: Valencia right now feels relatively normal. After the flooding event, we had a few weeks that were very challenging, because we lost two of the main entries into Valencia and the supermarkets were empty. What has been really affected are the outskirts of Valencia in the south. The situation is really far from normal. The roads are still full of mud, and because it has been over a month, it's very difficult to clean because it has dried out. All the ground level shops and supermarkets are gone so it’s very difficult to get food and to live a normal life. It's a bit heartbreaking.

NR: And there's still water in underground areas that's being pumped out, is that right?

MC: Yes, we still need to pump out lots of water – it's very difficult to know if they can pump, because there are lots of buildings with structural damage.

NR: Tell us why Valencia itself was relatively untouched in comparison to the outskirts of the city.

MC: The River Turia used to run through the middle of the city. In 1957 Valencia had a really severe flood that destroyed most of the city so after that flooding event, it was decided to divert the Turia through the south of Valencia. When it was diverted the capacity was increased from around 2,000 cubic meters per second to over 4,000 cubic meters per second.

NR: What does the diverted Turia look like most of the time?

MC: It’s a concrete structure, 250 meters wide, that most of the time is empty. I don't think that I have ever seen even one drop of water in that diversion. And what you could see is lots of biodiversity, trees and vegetation thriving in that channel. It looks like a city park under normal weather condition. Many people have questioned why we have this massive concrete structure through the south of Valencia that’s always empty. But it has proved that when it's needed, it's very useful.

These gardens are in the former channel of the Turia River

NR: And also reinforces the importance of talking to people about water and the water environment that they live in.

MC: However, south of the Turia, we have a system of water courses called the Rambla del Poyo that, most of the time, are completely dry. They usually take water when we have heavy rainfall. What is very interesting is the difference in elevation: between the high point and the low point is 1,000m, over only 40km in length. That is a very steep system, and from a hydraulics point of view, that means that water is going to move really, really quickly. In this system, there is no hydraulic structure to control the flows. So if there is rainfall in one point, it's just going to move along the system without any control. This system discharges into a lagoon called La Albufera.

South of the Rambla del Poyo we have the River Magro. It has really low flow during normal condition, but it can take really high flows during a storm. And in that river, we have a dam that can regulate the flows. That dam was built between the sixties and seventies. Just before the storm last October, that reservoir was only around 10 per cent full and in a matter of hours, it was full up, which is amazing.

NR: How big is that reservoir?

MC: That reservoir has a maximum capacity of 37 million cubic meters.

NR: That's a lot of water in a very short amount of time.

MC: A lot of flow was coming into the reservoir, and the dam was only allowing lower flows to go down a stream. When the reservoir got 100 per cent full, that means that there is no longer protection, and everything that was coming in was coming out, and we have floods downstream of the dam. But the effect downstream of the dam wasn't as bad as in the Rambla del Poyo, because in the Rambla del Poyo there was not any protection.

There’s much more where that came from, so listen to the full conversation here or search for Planet Possible in your favourite podcast app or on Spotify.