A comparative analysis between two pluvial flood events in Barcelona (Spain). An example of a success story

The city of Barcelona is severely affected by pluvial floods, for which the risk management can be further improved. To provide essential information about pluvial flood risk we compare two events that occurred in 1995 and 2018 and put these into context of all convective precipitation events between 2013 and 2018 in Barcelona. The objective is to identify the main drivers of pluvial flood impact and the most flood prone areas. These results will help to further improve pluvial flood risk management in Barcelona, e.g. by developing targeted preparedness and empowerment campaigns.

The event comparison followed the paired event approach (Kreibich et al. 2017). In the 1995 event, the surface runoff of the streets caused a fatality in the Eixample quartier, a total of 2,500 calls were registered to the emergency services, 128,000 subscribers suffered cuts of light, 2 blocks of houses were evacuated, and numerous low floors were flooded.  33.6 Million €₂₀₁₈ were paid by the national insurance company, CCS, to compensate insured losses in Barcelona. The 1995 episode marked a turning point in the development of the sewerage in the city. Although the maximum 5-min intensity in the 1995 event was 235 mm/h in front of 211 mm/h in the 2018 event, the maximum rainfall recorded in 20 min (155,4 mm/h versus 169,8 mm/h, respectively) and 60 min (78,6 mm/h versus 88,1 mm/h), as well as the “average water volume precipitated over the city” (376,5 m³ versus 457,1 m³) was superior in the second event. However, in the 2018 event, only 294 emergency phone calls were received, mainly due to flooding of low plants and basements, water leaks or fallen trees; and 3.5 Million €₂₀₁₈ were paid by the CCS. This analysis shows the effectiveness of the mitigation measures taken in the city after the 1995 flood event that have diminished the vulnerability. The analysis of the 207 convective pluvial events registered by the city's drainage network between 2013 and 2018, with a focus on the 58 events for which radar images are available (Esbrí et al., 2021) provides information on the city quartiers which are most endangered by pluvial floods. Conclusion shows that the structural and non-structural improvements applied in Barcelona are a good example for other cities with similar characteristics, although the improvement in awareness, empowerment and communication with the population is still pending, mainly in the most affected quartiers of the city.

This work has been done in the framework of the I-CHANGE (H2020-2020 Prop.101037193) European project and the C3-RiskMed (PID2020-113638RB-C22) research project, funded by the Spanish Ministry of Science and Innovation.

References.

Kreibich, H., S. Vorogushyn, J.C.J.H. et al. 2017. Adaptation to flood risk – results of international paired flood event studies. Special collection “Avoiding Disasters: Strengthening Societal Resilience to Natural Hazards” in the journal Earth’s Future. Earth’s Future,5,953–965, doi:10.1002/2017EF000606.

Esbrí, L.; Rigo, T.; Llasat, M.C.; Aznar, B. Identifying Storm Hotspots and the Most Unsettled Areas in Barcelona by Analysing Significant Rainfall Episodes from 2013 to 2018. Water 2021, 13, 1730. https://doi.org/10.3390/w13131730.