Monte Carlo analysis of probability of inundation of Rome

Rome's monumental centre has often been inundated by Tiber River. In the last decades of the 19th century, river walls were erected to protect Rome from floods so that the last significant flood, which occurred in 1937, caused only marginal damages. Although the probability of inundation of the city seems to be now substantially reduced, the evaluation of the residual risk is still worthwhile. With this aim, rainfall, rainfall–runoff, river flood propagation and street flooding processes are simulated in detail to produce the inundation scenarios analysed by the Monte Carlo method. The study shows that severe floods, having a return period greater than 180 years, overtop both the left and right river banks and inundate the northern outskirts of Rome, while extreme events, with 1000 years return period, submerge large parts of the monumental centre of Rome.