Résumé
Lateral flow L(t) is a major process during flood events, which can be either gains (positive) or losses (negative) to the channel. The inverse problem consists of evaluating L(t) knowing the inflow I(t) and the outflow O(t) on a channel. However L(t) is very difficult to measure on real channels, and we are always not sure to which extent the evaluated L(t) is close to the real one. This paper aims at evaluating L(t) in a channel using the analytical solution of the inverse problem of the Hayami diffusive wave equation (DWE) with L(t) uniformly distributed along the channel. We conceived and built a novel experimental channel where I(t), O(t) and L(t) are highly controlled at 1 s time step and we realize 62 experimental hydrograph scenarios corresponding to different shapes of I(t) and L(t). We validate the hypotheses of both the DWE Hayami model and the corresponding inverse model (with very high criteria functions values for a large majority of scenarios) which reflects the ability of the DWE inverse model to reproduce complex lateral flow hydrograph dynamics. We discuss the limits of application of the DWE especially for short wave lengths. The coupled experimental-modelling approach proposed herein opens promising perspectives regarding the evaluation of lateral flow on real channels.