Inferring the flood frequency distribution for an ungauged basin using a spatially distributed rainfall-runoff model

摘要

The estimation of the peak river flow for ungauged river sections is atopical issue in applied hydrology. Spatially distributed rainfall-runoffmodels can be a useful tool to this end, since they are potentially able tosimulate the river flow at any location of the watershed drainage network.However, it is not fully clear to what extent these models can providereliable simulations over a wide range of spatial scales. This issue isinvestigated here by applying a spatially distributed, continuous simulationrainfall-runoff model to infer the flood frequency distribution of theRiarbero River. This is an ungauged mountain creek located in northern Italy,whose drainage area is 17 km2. The hydrological model is first calibratedby using a 1-year record of hourly meteorological data and river flowsobserved at the outlet of the 1294 km2 wide Secchia River basin, of whichthe Riarbero is a tributary. The model is then validated by performing a100-year long simulation of synthetic river flow data, which allowed us tocompare the simulated and observed flood frequency distributions at theSecchia River outlet and the internal cross river section of Cavola Bridge,where the basin area is 337 km2. Finally, another simulation of hourlyriver flows was performed by referring to the outlet of the Riarbero River,therefore allowing us to estimate the related flood frequency distribution.The results were validated by using estimates of peak river flow obtained byapplying hydrological similarity principles and a regional method. Theresults show that the flood flow estimated through the application of thedistributed model is consistent with the estimate provided by the regionalprocedure as well as the behaviors of the river banks. Conversely, the methodbased on hydrological similarity delivers an estimate that seems to be not asreliable. The analysis highlights interesting perspectives for theapplication of spatially distributed models to ungauged catchments.