RiverFlood-1D v 1.0: coupling parabolic and backwater (PAB) scheme and Muskingum-Cunge model for river flood routing, with application to the Po River (Italy)

RiverFlood-1D is a discharge routing model for simulating flood wave propagation in rivers with arbitrary cross-section geometries. It couples the parabolic-backwater (PAB) scheme with the Muskingum-Cunge (MC) approach, dynamically updating routing parameters at each computational step based on steady water surface profiles that account for downstream conditions. The model was verified against four test cases, including compound channels, mixed flow regimes, and a dam-break experiment with highly irregular cross sections. It was then applied to a real flood event along a 60 km reach of the Po river (Italy, April 2009), achieving mean absolute percentage errors of 0.230 and 0.119 for discharge and water depth, respectively, comparable to HEC-RAS (0.210 and 0.080). RiverFlood-1D remained stable in the dam-break test where HEC-RAS's unsteady solver failed to converge. The model combines accuracy similar to full dynamic-wave solvers with greater numerical robustness, making it well suited for operational, real-time flood-forecasting applications.