Estimation of flood design hydrographs using bivariate analysis (copula) and distributed hydrological modelling

Abstract

Abstract. In this paper a procedure to derive Flood Design Hydrographs (FDH) using a bivariate representation of rainfall forcing (rainfall duration and intensity) using copulas, which describe and model the correlation between these two variables independently of the marginal laws involved, coupled with a distributed rainfall-runoff model is presented. Rainfall-runoff modelling for estimating the hydrological response at the outlet of a watershed used a conceptual fully distributed procedure based on the soil conservation service – curve number method as excess rainfall model and a distributed unit hydrograph with climatic dependencies for the flow routing. Travel time computation, based on the definition of a distributed unit hydrograph, has been performed, implementing a procedure using flow paths determined from a digital elevation model (DEM) and roughness parameters obtained from distributed geographical information. In order to estimate the return period of the FDH which give the probability of occurrence of a hydrograph flood peaks and flow volumes obtained through R-R modeling has been statistically treated via copulas. The shape of hydrograph has been generated on the basis of a modeled flood events, via cluster analysis. The procedure described above was applied to a case study of Imera catchment in Sicily, Italy. The methodology allows a reliable and estimation of the Design Flood Hydrograph and can be used for all the flood risk applications, i.e. evaluation, management, mitigation, etc.