Impacts of small scale rainfall variability in urban areas: a case study with 1D and 1D/2D hydrological models in a multifractal framework

摘要

In this paper the sensitivity to small scale unmeasured rainfall variability (i.e. at scales smaller than 1km by 1km by 5min in time, which are usually available with C-band radars) of a 1D/2D model with a 10m resolution and a semi-distributed 1D model of the same 1.47km(2) urban area is analyzed. The 1D/2D model is the open source numerical platform Multi-Hydro, which couples (open source) distributed models of involved hydrological/hydraulic processes. The methodology implemented to evaluate the uncertainties consists of generating an ensemble of realistic rainfall fields downscaled to a resolution of 12.3m in space and 18.75s in time with the help of a stochastic universal multifractal model. The corresponding ensemble of hydrographs is then simulated. It appears that the uncertainty is significant and that Multi-Hydro unveils much more uncertainty than the simpler 1D model. This points out a need to develop high resolution distributed modelling in urban areas.