Scaling properties of flood hydrographs and their use to derive design flood hydrographs

摘要

For planning water management projects, design flood hydrographs are required. These hydrological tools are inputs for hydraulics modelling which provide a delineation of the flooded areas. These hydrographs are mostly relative to the instantaneous discharge associated to a predetermined return period and their shape is computed by mathematical formulations. In this paper, a method for deriving hydrological scenarios is presented. This method is based on the analysis of the observed hydrographs. Parameters describing the shape of the hydrographs are defined : K, the scale coefficient, ECARTY, a parameter characterising the spread near the peak and, ASY, the asymmetric parameter and a duration δ which reflects the dynamic of the observed floods. ECARTY represents the concentration of the volume around the peak discharge and ASY gives information about the location of the volume in comparison with the peak. Starting with the assumption of invariant shape of hydrographs with the runoffs magnitude, reference scenarios are built by using the average of observed hydrographs, which are preliminary standardised by the mean volume flowing over a duration δ . An application on catchments with different hydrological regimes is carried out to evaluate the relevance of shape invariant assumption. Finally, design flood projects obtained with this method are computed by reference discharges quantiles and compared to observed flood events in term of shape characteristics.