Fast ERT to estimate pollutants and solid transport in water flow: a laboratory experiment.

The understanding and evaluation of the phenomena related to pollutants diffusion, solid transport or lithic material deposition within a river have a prominent role in hydraulics and fluvial geomorphology. In this respect, the direct measurement of the amount of transported material is certainly one of the most difficult tasks in the field of river hydraulics due to the heterogeneity and representativeness of the samples. In this paper, we investigate the applicability of a very fast (about ten seconds or less), non-invasive electrical resistivity tomography to identify and estimate pollutant and solid transport variations in a fast water flow. To do this, three experimental tests, in a laboratory channel with a flow rate of 0.5 m/s, are presented using both a pollutant flow and different types of solid transport (fine and coarse sands). Data are interpreted by means of classical models that relate the variation in electric conductivity to variations in concentration or in volume fraction of suspended material. Whereas the identification and positioning of the pollutant or solid transport is successful, the estimation of governing parameters still remains mainly qualitative.