Modelling the Erosion of Mixtures of Organic and Granular In-Sewer Sediments

Sewer flow quality modelling software uses equations derived from uniform granular sediment studies. Actual sewer sediments are mixtures of organic and granular material and interactions between these fractions may account for the poor performance of current models. Laboratory experiments were carried out using surrogate sewer sediment mixtures to examine interactions between the fractions. Impaction of the bed surface by saltating granular particles increased the erosion of fine grained organic sediments. Changes in the composition of the bed surface over the duration of a test resulted in change in the availability of fine grained sediment. An existing model was further developed to attempt to account for these mechanisms, using a empirically based correction factor.