INVERSE ESTIMATION OF BED ROUGHNESS COEFFICIENTS IN OPEN-CHANNELS WITH FLOOD PLAINS BY USING ADJOINT SHALLOW-WATER MODEL

Abstract

This study describes the methodology on an inverse estimation of the bed roughness coefficients in open-channels with flood plains. The coefficients are identified by an adjoint shallow-water model and an optimal control theory. Several twin experiments were carried out with the synthetic data in order to validate the method. The data assimilated consists of values of the water level and depth-averaged velocity. The results showed that the coefficients can be accurately predicted with the velocity data, while the estimation fails with the water level data. This is because the cross-sectionally distributed bed roughness does not always influence the lateral profile of the water level, but the local velocity field. Namely, the relation between the lateral profile of the water level and the bed roughness turns out to be non-unique in open-channels with flood plains.