Author(s): Ivan Collado Fernandez; Eva Crego Liz; Sandra Ruiz Navarro

Linked Author(s): Ivan Collado Fernandez

Keywords: Delta; Tordera; Gloria; Leeves; 2D

Abstract: In 2018, the Catalan Agency of Water (ACA) promoted the “Project Management of the levees of the Tordera river”. One of the main objectives of this project is the reorganization of the exiting levees along the Tordera River in order to analyse if the recovery of the previous flooding areas could reduce the floodrisk in those villages located downstream. The project developed several detailed hydraulic models that operates with 2D and unsteady steady states scenarios. The behaviour of the existing leeves and the feasible actions were analysed in order to redefine their layout and meet the objective proposed. One of the most notable areas of this study is the Tordera Delta. The whole area of the Tordera Delta is under a significant urban, touristic and infrastructure development pressure. This fact makes it necessary to dispose of a very detailed hydraulic model for delimiting flood areas in order to understand how flooding takes place to deal with the reduction of the risk of flooding. The difficulty of develop this hydraulic model is increased by the lack of historical flood data that made it difficult to verify the results with real events. The elaboration of the hydraulic model of the Tordera Delta was completed in August 2019, and just 5 months later, the Gloria storm took place. The Gloria storm took place between 20 and 23 January 2020 and had a special impact on the Tordera Delta where 807 hectares were flooded, affecting the municipalities of Blanes, Tordera, Malgrat de Mar and Palafolls, furthermore 2 bridges collapsed. Extensive graphic material, aerial photographs and videos in helicopters were collected from the floods, which have made it possible to compare the results obtained in the previous hydraulic model with a real success. One of the conclusions that has been drawn from the study and have been verified by the floods of the Gloria is that flood levels did not exceed the coronation level of the current levees. However, the entire delta was flood because the flood came from the river overflowing several miles upstream. Another conclusion is that the transport infrastructure that crosses the river generates significant levels of flooding upstream, and therefore acting with a certain effect of rolling downstream where the Delta is located. On the other hand, the Gloria storm redefined a new Delta with the contribution of sediments that had not been produced for decades. The validation of the results with this event, will allow to define the framework of actions in the Delta of Tordera to make compatible the activities that take place there, as well as the development of infrastructures having clear what is its affectation on the risk of flooding of the area.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022613

Year: 2022