*2.1. The E*ff*ects of Climate Change on Maximum Rainfall Intensity in Barcelona*

Recently, the Climate Research Foundation (Fundación de Investigación del Clima; hereafter, FIC from the acronym in Spanish) provided climate projections and predictions for different climate variables in Barcelona, the results of which are summarized in Figure 2. These results confirm the same trends as other previous studies developed for the city and are in line with the data from the last Climate Plan published by Barcelona City Council [8]. According to the data provided by FIC, phenomena such as extreme rainfall, heatwaves and droughts could experience significant increases due to an acceleration of the hydrological cycle [6,9].

**Figure 2.** Extremes compass rose for Barcelona: maximum point change in extreme climate events over the century, taking into account return periods between 2 and 100 years. The center represents no changes, and the edge corresponds to an increase of 100% for every variable except for heat wave days (the border is +1000%) and extreme temperature (the border is +10 ◦C). Thick lines represent the median scenario, and the shaded area is the uncertainty region (5–95%).

Particularly, in the case of maximum rainfall intensities and the horizon of 2071–2100 for the city of Barcelona, the value of the coefficient of climate change (defined as the ratio between future and

current maximum intensities, for certain return periods and time intervals) [10,11] was found to be in a range between 1.07 and 1.26 depending on the frequency and duration of each maximum rainfall intensity (Figure 3).

**Figure 3.** Fiftieth percentiles of the climate change coefficients obtained for different rainfall durations and return periods for the horizon 2071–2100 for the city of Barcelona [6].

These results were obtained using statistical spatial and temporal downscaling techniques on 20 future pluviometric series provided by 10 general atmospheric circulation models, forced by Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios and previously validated for a historical control period (1976–2005) [6]. The climate change coefficients in Figure 3 represent the 50th percentile of the results obtained.

Once these climate change coefficients were obtained, they were applied to synthetic storms with different return periods (T1, T10, T50, T100 and T500) used for the last drainage master plan of the city of Barcelona [11] obtained through the alternating blocks method. Figure 4 shows the urban drainage Barcelona project design storm for a return period of 10 years with a duration of approximately 2 h and 30 min after the application of climate change coefficients for each different rainfall duration.

**Figure 4.** Urban drainage Barcelona project design storm with a return period of 10 years and a duration of 2 h and 35 min [6].
