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A stem spacing‑based non‑dimensional model for predicting longitudinal dispersion in low‑density emergent vegetatio

Sonnenwald F., Stovin V., Guymer I.

Acta Geophysica

2019

Vol. 67, no. 3

943--949

Predicting how pollutants disperse in vegetation is necessary to protect natural watercourses. This can be done using the one-dimensional advection dispersion equation, which requires estimates of longitudinal dispersion coefficients in vegetation. Dye tracing was used to obtain longitudinal dispersion coefficients in emergent artificial vegetation of different densities and stem diameters. Based on these results, a simple non-dimensional model, depending on velocity and stem spacing, was developed to predict the longitudinal dispersion coefficient in uniform emergent vegetation at low densities (solid volume fractions < 0.1). Predictions of the longitudinal dispersion coefficient from this simple model were compared with predictions from a more complex expression for a range of experimental data, including real vegetation. The simple model was found to predict correct order of magnitude dispersion coefficients and to perform as well as the more complex expression. The simple model requires fewer parameters and provides a robust engineering approximation.

A practical model to describe temporal variations in total suspended solids concentrations in highway runoff

Stovin V., Guymer I.

Acta Geophysica

2013

Vol. 61, no. 3

706--731

Techniques to predict temporal variations in concentrations and loads of suspended solids from highway runoff are required to estimate impacts on receiving water ecology and to inform the design of interception/treatment devices. A recent UK study included the collection of rainfall, highway runoff rates and sediment load and quality data from six different sites where motorway runoff drained directly into a receiving watercourse. This data set is used to critically evaluate a previously-published model (Kim et al. 2005) aimed at predicting temporal variations in runoff quality. The comparisons, based on discrete samples collected during 21 storm events, suggest that a simplification of the model, requiring just two parameters, provides a robust estimate of temporal variations in total suspended solids (TSS). Generic parameter values are provided, and the model’s application is illustrated. The model captures first flush effects well, but the identified generic parameters fail to fullypredict the variation in absolute TSS values that are observed in practice.