Author(s): Gabriele Farina; Riccardo Bonomelli; Marco Pilotti

Linked Author(s): Riccardo Bonomelli, Marco Pilotti

Keywords: Dam break wave propagation; Case study; Shallow water; Numerical simulation

Abstract: Title: Effects of anthropic changes on the propagation of the Gleno dam break wave in the Valle Camonica Floodplain Authors: Farina, G., Bonomelli, R., Pilotti, M. Theme: 8.c. Flood risk assessment, mitigation and adaptation measures Text: The catastrophic Gleno dam break flood, which occurred in 1923, claimed the lives of about 500 people. The event has been investigated in the literature considering the 20 km long steep alpine valley separating the dam location from the hamlet of Corna (Pilotti et al., 2011; Milanesi and Pilotti, 2021). In this contribution, we investigate the propagation of the flood wave from Corna, where the computed hydrograph from previous investigation provides the upstream boundary condition, as far as the Lake Iseo. In the middle, the flood wave with a peak higher than 2200 m3/s (1.6 times the T500 discharge in the same location) and a volume of about 4*106 m3 swept a 10 km long stretch of floodplain in Valle Camonica before entering Lake Iseo. The wave caused a swift increase of the lake level, recorded at the lake outlet, 23 km from the tributary entrance. Accordingly, a suitable modeling of the propagation of the flood in the lake provides the unknown entering hydrograph, that can be used to crosscheck the accuracy of the simulation of the floodplain flooding of Valle Camonica. This study highlights some interesting features of extreme floods in a mountaing region: first, it completes the historical reconstruction of the Gleno dam break, computing the extent of the flooded areas on a modified bathymetric reconstruction of 1923 Valle Camonica. Second, the same flood is propagated on the bathymetry of present time Valle Camonica. The comparison highlights the difference in terms of hazard and of risk following 100 years of anthropic pressure and river training works in this valley. The simulation has been accomplished by using the well known HEC-RAS 2D software. Another important fallout of the modelling effort is the reconstruction of the 1923 original bathymetry of the river in Valle Camonica, compared with the present one, affected by 100 years or river training works. References Milanesi, L., and Pilotti, M., (2021). Coupling Flood Propagation Modeling and Building Collapse in Flash Flood Studies, J. Hydraulic Engrg., ASCE, DOI: 10.1061/(ASCE)HY.1943-7900.0001941. Pilotti, M., Maranzoni, A., Tomirotti, M., and Valerio, G. (2011). The 1923 Gleno dam-break: case study and numerical modelling, J. Hydraulic Engrg., ASCE, 137, 480. Keywords: Dam break wave propagation, Case study, Shallow water, Numerical simulation

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221092

Year: 2022