Effect of vegetation on floods: the case of the river Magra

Andrés Vargas-Luna, Riccardo Benifei, Luca Solari, Gertjan Geerling, Mijke van Oorschot

Friday 3 july 2015

14:30 - 14:45h at North America (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 16F. Environment - Ecohydraulic

The study of the influence of vegetation on hydraulic risk is of primary importance in river planning and decision making. In this work, we investigate the effects of channel and riparian vegetation on the catastrophic flood event that occurred on 25/10/2011 in the river Magra, (Tuscany region, Italy). This 200-year-return-period flood had produced the loss of many human lives and enormous material damages, especially in the town of Aulla. Preliminary hydraulic studies, carried out with 1D models, showed that riparian vegetation located on the floodplain strongly influenced the flood by increasing the water levels of about 0.8 m in the river reach facing the town of Aulla, thus producing overflow of the embankments and flooding of large urbanized areas. Based on these results, the Tuscany region decided to remove the floodplain vegetation as a preventive action. Ecological damages and major changes in river morphodynamics were reported after removing the riparian vegetation. This work addresses the effectiveness of different flood mitigation strategies by using a more detailed hydrodynamic model, i.e. the 2D morphological model Delft3D which includes a sub-model for evaluating the presence of various species of vegetation in different areas of the river.