Assessing the effect on flood frequency of land use change via hydrological simulation (with uncertainty)

The present work aims to assess the effects that land use change, which have affected a wide portion of Italy in the second part of the last century, have induced on the flood frequency regime. The analysis has been carried out by applying a spatially distributed rainfall-runoff model to generate synthetic river flow series. Reference is made to different historical land use scenarios of the Samoggia River basin (178 km2 in area), located in the Apennines mountains (Italy). The man induced extensive land use changes, which have affected the drainage basin during the last decades, have been assessed by using land use maps which refer to the years 1955, 1980 and 1992. By simulating the Samoggia River flood flows for the different land use scenarios, the variations of the peak flow regime, due to the increasing human activity, have been investigated. Finally these variations have been compared with the magnitude of the simulation uncertainty. The results indicate that the sensitivity of the floods regime to land use change decreases for increasing return period of the simulated peak flow. By considering peak flows with return period ranging from 10 to 200 years, the effects of human activity seem to be noteworthy. However, these results are to be interpreted cautiously, in light of the uncertainty that affects hydrological simulation studies.