Move the levees back to reduce flood risk — the case of the Tordera River Basin
Eva Crego Liz from Agència Catalana de l’Aigua (ACA) illustrates the case of the Tordera Delta and the feasibility studies made to diminish the flood risk in this RECONECT demonstrator.
Short description of your area (geographical context, morphological problems and goals of the NBS implementations)
The Tordera River Basin is one of the main watersheds in Catalonia, Spain, still unregulated. It has a typical Mediterranean rain regime (scarce and irregular) and flash floods usually occur. Vulnerable activities occupy flood-prone areas as the middle part of the basin is highly industrialized, while the Delta is a popular tourist spot with different campsites. Besides, the Delta is an important area for agricultural production. In this context, the main goal of the NBS implementations in the basin has to be the reduction of flood risk in highly vulnerable areas, reducing the impact of floods on economic activities.
On the other hand, part of the Tordera River Basin has been designated as Natura 2000 site, while the river reach where the NBS is intended to be developed has been identified as a highly modified water body with a bad ecological status in the context of the EU Water Framework Directive. In this sense, the second main goal to be reached with the implementation of NBS is the conservation of the environmental values associated to the area, contributing as well to the improvement of the ecological status of the water body.
Status of work
The Catalan Water Agency (ACA) is currently developing the “Tordera Levee Management Plan”, a measure included in the first “Flood Risk Management Plan of the River Basin District of Catalonia”. The aim of the Levee Management Plan is, firstly, to assess the flood hazard at the watershed scale and, secondly, to evaluate the feasibility of different flood protection measures that help to reduce flood risk at the basin level. In this sense, NBS have been prioritized over more conventional type of solutions.
We concluded the flood hazard assessment in late June 2019. The results were published in December 2019, in the context of the “Flood Hazard and Flood Risk Maps” of the second cycle of implementation of the EU Floods Directive. In February 2020, we finished the pre-feasibility studies of different flood protection measures. In this respect, the results of our analysis show that giving more room to the river in the final reach of the Tordera will help to reduce flood risk in the Tordera Delta.
So, now we are conducting a feasibility study and a cost-benefit analysis of a NBS consisting in setting back the levees of the final reach of the Tordera to give more space to the river, on the one hand, while trying to improve and restore the hydro-morphological status of the river reach on the other hand.
ACA organised the first RECONECT workshop: which topics have been touched?
We had in February our first RECONECT workshop, where we presented to key stakeholders the RECONECT project and the feasibility studies we are conducting in the context of the Tordera Levee Management Plan. The workshop was held just after the storm Gloria hit Eastern Spain and the Tordera River Basin, causing huge economic damages in the area (e.g. two bridges collapsed, loss of crops and agricultural infrastructure like greenhouses, important damages in tourist infrastructure like campsites). Farmers, campsite managers, factory managers, representatives from municipalities, environmental organizations, research centres, and general public attended the meeting. So, the discussion following the workshop was very controversial, as the interests and views of different stakeholders in the audience were sometimes confronted. In this sense, we can say that the meeting was successful. But the need for more spaces of debate became evident, where to expose different opinions and discuss the Tordera River Delta, its problems and its future.
Can you identify other areas where to use the same approach?
Definitely. We are also developing a levee management plan for the Ter and Muga river basins, in which the suitability of NBS for flood risk reduction is being analysed. We are trying to prioritize NBS over grey solutions for flood risk protection, when possible, as the measures we execute have to comply not only with the EU Floods Directive but with EU Water Framework Directive as well. In this sense, the environmental co-benefits that NBS can provide are key to enhance or at least to not deteriorate the ecological status of a water body.