Issue 46

M. L. Puppio et alii, Frattura ed Integrità Strutturale, 46 (2016) 190-202; DOI: 10.3221/IGF-ESIS.46.18 194 The average pluviometric data of the stations in Bocca D’Arno, Santa Luce, Livorno Mareograph and Pisa Agraria give the return periods (Tab. 4). (a) (b) Figure 5 : Rainfalls Scheme. Map of 24hours accumulated rainfalls - from the 0.00 of the 11th September 2017 (a) ; Station of Bocca d’Arno, Pisa - 1.00 m above the sea level (b) . Name of Station Duration of rainfalls (mm) 15 min 1 hour 2 hours 3 hours Quercianella 42.4 121.8 188.6 206.2 Valle Benedetta 38.4 120.8 210.2 235.0 Santa Luce 23.0 66.4 98.2 105.8 Castellina Marittima 40.2 89.6 109.6 122.2 max 42.4 121.8 210.2 235.0 Table 3 : Duration of rainfalls. Longest duration 1/4 1 2 3 hours Return period 16 756 2036 1240 years Table 4 : Return period of the more severe events. Number Name of the bridge Water catchment [km 2 ] Hydraulic pattern [km] Average slope Concentration time [h] 1 Tre Ponti 21.2 3.7 0.010 2.0 2 Chioma 18.6 9.8 0.010 2.7 3 Limoncino 4.9 8.6 0.019 1.7 Table 5 : Hydrological main data. Estimated return periods associated to 1 and 3 hours rainfalls recorded during this event are much longer than 200 years (estimated numeric values of 500-1.000 years). It should be specified that the statistic data related to rainfalls in the [0, 200] year period do not allow their extrapolation, though providing a rather significant indicator.