Hydrodynamic and morphodynamic impacts of a flood discharge tunnel in the Tagus estuary

10/09/2017

Due to frequent flooding in Lisbon, in particular in the lower areas such as Alcântara and Chelas, and the recent worsening of these floods because of climate change and increasing population, there is a need to develop solutions that reduce the impacts of flooding. One such measure, as outlined in the General Drainage Plan for Lisbon 2016 - 2030 (Plano Geral de Drenagem de Lisboa 2016 - 2030 or PGDL) is the construction of a rainwater drainage tunnel which would collect excessive or flooding rain water and discharge it in the Tagus river’s estuary, designed to drain emergency water loads that the standard drainage system currently in place is not able to handle. Using a numerical modelling software (MOHID), this tunnel’s discharge was simulated, with the goal of predicting potential hydrodynamic (changes to the velocity field and modulus and dispersion of a generic conservative pollutant) and morphodynamic (changes to bathymetry, sediment dispersion) impacts on the Tagus river’s estuary. The simulated results suggest that hydrodynamic impacts are both localized and temporary, as 2 hours after the discharge stops, the effects are very small or negligible, whereas during the discharge, the approximate maximum radius of the affected area is 1150m. As for the morphodynamic impacts, the effects of the discharge are very low throughout the simulation, as the discharge doesn’t occur at a sufficient enough depth to significantly affect the bottom. Therefore, these impacts, as simulated, are considered to have a low significance in the general context of the PGDL.

Authors in the community:

• 

  P

  Pedro Miguel Parreira Russo da Costa e Vasconcelos

  ist169702

Supervisors of this institution:

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  M

  Marcos Duarte Mateus

  ist32449

chemical-engineering - Chemical engineering

por - Portuguese

Instituto Superior Técnico